The Tor Browser: comparison media/libpng/pngwutil.c

--1:000000000000
+:79be750f98ac
+/* pngwutil.c - utilities to write a PNG file
+*
+* Last changed in libpng 1.6.2 [April 25, 2013]
+* Copyright (c) 1998-2013 Glenn Randers-Pehrson
+* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
+* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
+*
+* This code is released under the libpng license.
+* For conditions of distribution and use, see the disclaimer
+* and license in png.h
+*/
+#include "pngpriv.h"
+#ifdef PNG_WRITE_SUPPORTED
+#ifdef PNG_WRITE_INT_FUNCTIONS_SUPPORTED
+/* Place a 32-bit number into a buffer in PNG byte order.  We work
+* with unsigned numbers for convenience, although one supported
+* ancillary chunk uses signed (two's complement) numbers.
+*/
+void PNGAPI
+png_save_uint_32(png_bytep buf, png_uint_32 i)
+{
+buf[0] = (png_byte)((i >> 24) & 0xff);
+buf[1] = (png_byte)((i >> 16) & 0xff);
+buf[2] = (png_byte)((i >> 8) & 0xff);
+buf[3] = (png_byte)(i & 0xff);
+}
+/* Place a 16-bit number into a buffer in PNG byte order.
+* The parameter is declared unsigned int, not png_uint_16,
+* just to avoid potential problems on pre-ANSI C compilers.
+*/
+void PNGAPI
+png_save_uint_16(png_bytep buf, unsigned int i)
+{
+buf[0] = (png_byte)((i >> 8) & 0xff);
+buf[1] = (png_byte)(i & 0xff);
+}
+#endif
+/* Simple function to write the signature.  If we have already written
+* the magic bytes of the signature, or more likely, the PNG stream is
+* being embedded into another stream and doesn't need its own signature,
+* we should call png_set_sig_bytes() to tell libpng how many of the
+* bytes have already been written.
+*/
+void PNGAPI
+png_write_sig(png_structrp png_ptr)
+{
+png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
+#ifdef PNG_IO_STATE_SUPPORTED
+/* Inform the I/O callback that the signature is being written */
+png_ptr->io_state = PNG_IO_WRITING | PNG_IO_SIGNATURE;
+#endif
+/* Write the rest of the 8 byte signature */
+png_write_data(png_ptr, &png_signature[png_ptr->sig_bytes],
+(png_size_t)(8 - png_ptr->sig_bytes));
+if (png_ptr->sig_bytes < 3)
+png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
+}
+/* Write the start of a PNG chunk.  The type is the chunk type.
+* The total_length is the sum of the lengths of all the data you will be
+* passing in png_write_chunk_data().
+*/
+static void
+png_write_chunk_header(png_structrp png_ptr, png_uint_32 chunk_name,
+png_uint_32 length)
+{
+png_byte buf[8];
+#if defined(PNG_DEBUG) && (PNG_DEBUG > 0)
+PNG_CSTRING_FROM_CHUNK(buf, chunk_name);
+png_debug2(0, "Writing %s chunk, length = %lu", buf, (unsigned long)length);
+#endif
+if (png_ptr == NULL)
+return;
+#ifdef PNG_IO_STATE_SUPPORTED
+/* Inform the I/O callback that the chunk header is being written.
+* PNG_IO_CHUNK_HDR requires a single I/O call.
+*/
+png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_HDR;
+#endif
+/* Write the length and the chunk name */
+png_save_uint_32(buf, length);
+png_save_uint_32(buf + 4, chunk_name);
+png_write_data(png_ptr, buf, 8);
+/* Put the chunk name into png_ptr->chunk_name */
+png_ptr->chunk_name = chunk_name;
+/* Reset the crc and run it over the chunk name */
+png_reset_crc(png_ptr);
+png_calculate_crc(png_ptr, buf + 4, 4);
+#ifdef PNG_IO_STATE_SUPPORTED
+/* Inform the I/O callback that chunk data will (possibly) be written.
+* PNG_IO_CHUNK_DATA does NOT require a specific number of I/O calls.
+*/
+png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_DATA;
+#endif
+}
+void PNGAPI
+png_write_chunk_start(png_structrp png_ptr, png_const_bytep chunk_string,
+png_uint_32 length)
+{
+png_write_chunk_header(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), length);
+}
+/* Write the data of a PNG chunk started with png_write_chunk_header().
+* Note that multiple calls to this function are allowed, and that the
+* sum of the lengths from these calls *must* add up to the total_length
+* given to png_write_chunk_header().
+*/
+void PNGAPI
+png_write_chunk_data(png_structrp png_ptr, png_const_bytep data,
+png_size_t length)
+{
+/* Write the data, and run the CRC over it */
+if (png_ptr == NULL)
+return;
+if (data != NULL && length > 0)
+{
+png_write_data(png_ptr, data, length);
+/* Update the CRC after writing the data,
+* in case that the user I/O routine alters it.
+*/
+png_calculate_crc(png_ptr, data, length);
+}
+}
+/* Finish a chunk started with png_write_chunk_header(). */
+void PNGAPI
+png_write_chunk_end(png_structrp png_ptr)
+{
+png_byte buf[4];
+if (png_ptr == NULL) return;
+#ifdef PNG_IO_STATE_SUPPORTED
+/* Inform the I/O callback that the chunk CRC is being written.
+* PNG_IO_CHUNK_CRC requires a single I/O function call.
+*/
+png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_CRC;
+#endif
+/* Write the crc in a single operation */
+png_save_uint_32(buf, png_ptr->crc);
+png_write_data(png_ptr, buf, (png_size_t)4);
+}
+/* Write a PNG chunk all at once.  The type is an array of ASCII characters
+* representing the chunk name.  The array must be at least 4 bytes in
+* length, and does not need to be null terminated.  To be safe, pass the
+* pre-defined chunk names here, and if you need a new one, define it
+* where the others are defined.  The length is the length of the data.
+* All the data must be present.  If that is not possible, use the
+* png_write_chunk_start(), png_write_chunk_data(), and png_write_chunk_end()
+* functions instead.
+*/
+static void
+png_write_complete_chunk(png_structrp png_ptr, png_uint_32 chunk_name,
+png_const_bytep data, png_size_t length)
+{
+if (png_ptr == NULL)
+return;
+/* On 64 bit architectures 'length' may not fit in a png_uint_32. */
+if (length > PNG_UINT_31_MAX)
+png_error(png_ptr, "length exceeds PNG maxima");
+png_write_chunk_header(png_ptr, chunk_name, (png_uint_32)length);
+png_write_chunk_data(png_ptr, data, length);
+png_write_chunk_end(png_ptr);
+}
+/* This is the API that calls the internal function above. */
+void PNGAPI
+png_write_chunk(png_structrp png_ptr, png_const_bytep chunk_string,
+png_const_bytep data, png_size_t length)
+{
+png_write_complete_chunk(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), data,
+length);
+}
+/* This is used below to find the size of an image to pass to png_deflate_claim,
+* so it only needs to be accurate if the size is less than 16384 bytes (the
+* point at which a lower LZ window size can be used.)
+*/
+static png_alloc_size_t
+png_image_size(png_structrp png_ptr)
+{
+/* Only return sizes up to the maximum of a png_uint_32, do this by limiting
+* the width and height used to 15 bits.
+*/
+png_uint_32 h = png_ptr->height;
+if (png_ptr->rowbytes < 32768 && h < 32768)
+{
+if (png_ptr->interlaced)
+{
+/* Interlacing makes the image larger because of the replication of
+* both the filter byte and the padding to a byte boundary.
+*/
+png_uint_32 w = png_ptr->width;
+unsigned int pd = png_ptr->pixel_depth;
+png_alloc_size_t cb_base;
+int pass;
+for (cb_base=0, pass=0; pass<=6; ++pass)
+{
+png_uint_32 pw = PNG_PASS_COLS(w, pass);
+if (pw > 0)
+cb_base += (PNG_ROWBYTES(pd, pw)+1) * PNG_PASS_ROWS(h, pass);
+}
+return cb_base;
+}
+else
+return (png_ptr->rowbytes+1) * h;
+}
+else
+return 0xffffffffU;
+}
+#ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
+/* This is the code to hack the first two bytes of the deflate stream (the
+* deflate header) to correct the windowBits value to match the actual data
+* size.  Note that the second argument is the *uncompressed* size but the
+* first argument is the *compressed* data (and it must be deflate
+* compressed.)
+*/
+static void
+optimize_cmf(png_bytep data, png_alloc_size_t data_size)
+{
+/* Optimize the CMF field in the zlib stream.  The resultant zlib stream is
+* still compliant to the stream specification.
+*/
+if (data_size <= 16384) /* else windowBits must be 15 */
+{
+unsigned int z_cmf = data[0];  /* zlib compression method and flags */
+if ((z_cmf & 0x0f) == 8 && (z_cmf & 0xf0) <= 0x70)
+{
+unsigned int z_cinfo;
+unsigned int half_z_window_size;
+z_cinfo = z_cmf >> 4;
+half_z_window_size = 1U << (z_cinfo + 7);
+if (data_size <= half_z_window_size) /* else no change */
+{
+unsigned int tmp;
+do
+{
+half_z_window_size >>= 1;
+--z_cinfo;
+}
+while (z_cinfo > 0 && data_size <= half_z_window_size);
+z_cmf = (z_cmf & 0x0f) | (z_cinfo << 4);
+data[0] = (png_byte)z_cmf;
+tmp = data[1] & 0xe0;
+tmp += 0x1f - ((z_cmf << 8) + tmp) % 0x1f;
+data[1] = (png_byte)tmp;
+}
+}
+}
+}
+#else
+#  define optimize_cmf(dp,dl) ((void)0)
+#endif /* PNG_WRITE_OPTIMIZE_CMF_SUPPORTED */
+/* Initialize the compressor for the appropriate type of compression. */
+static int
+png_deflate_claim(png_structrp png_ptr, png_uint_32 owner,
+png_alloc_size_t data_size)
+{
+if (png_ptr->zowner != 0)
+{
+char msg[64];
+PNG_STRING_FROM_CHUNK(msg, owner);
+msg[4] = ':';
+msg[5] = ' ';
+PNG_STRING_FROM_CHUNK(msg+6, png_ptr->zowner);
+/* So the message that results is "<chunk> using zstream"; this is an
+* internal error, but is very useful for debugging.  i18n requirements
+* are minimal.
+*/
+(void)png_safecat(msg, (sizeof msg), 10, " using zstream");
+#     if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
+png_warning(png_ptr, msg);
+/* Attempt sane error recovery */
+if (png_ptr->zowner == png_IDAT) /* don't steal from IDAT */
+{
+png_ptr->zstream.msg = PNGZ_MSG_CAST("in use by IDAT");
+return Z_STREAM_ERROR;
+}
+png_ptr->zowner = 0;
+#     else
+png_error(png_ptr, msg);
+#     endif
+}
+{
+int level = png_ptr->zlib_level;
+int method = png_ptr->zlib_method;
+int windowBits = png_ptr->zlib_window_bits;
+int memLevel = png_ptr->zlib_mem_level;
+int strategy; /* set below */
+int ret; /* zlib return code */
+if (owner == png_IDAT)
+{
+if (png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_STRATEGY)
+strategy = png_ptr->zlib_strategy;
+else if (png_ptr->do_filter != PNG_FILTER_NONE)
+strategy = PNG_Z_DEFAULT_STRATEGY;
+else
+strategy = PNG_Z_DEFAULT_NOFILTER_STRATEGY;
+}
+else
+{
+#        ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
+level = png_ptr->zlib_text_level;
+method = png_ptr->zlib_text_method;
+windowBits = png_ptr->zlib_text_window_bits;
+memLevel = png_ptr->zlib_text_mem_level;
+strategy = png_ptr->zlib_text_strategy;
+#        else
+/* If customization is not supported the values all come from the
+* IDAT values except for the strategy, which is fixed to the
+* default.  (This is the pre-1.6.0 behavior too, although it was
+* implemented in a very different way.)
+*/
+strategy = Z_DEFAULT_STRATEGY;
+#        endif
+}
+/* Adjust 'windowBits' down if larger than 'data_size'; to stop this
+* happening just pass 32768 as the data_size parameter.  Notice that zlib
+* requires an extra 262 bytes in the window in addition to the data to be
+* able to see the whole of the data, so if data_size+262 takes us to the
+* next windowBits size we need to fix up the value later.  (Because even
+* though deflate needs the extra window, inflate does not!)
+*/
+if (data_size <= 16384)
+{
+/* IMPLEMENTATION NOTE: this 'half_window_size' stuff is only here to
+* work round a Microsoft Visual C misbehavior which, contrary to C-90,
+* widens the result of the following shift to 64-bits if (and,
+* apparently, only if) it is used in a test.
+*/
+unsigned int half_window_size = 1U << (windowBits-1);
+while (data_size + 262 <= half_window_size)
+{
+half_window_size >>= 1;
+--windowBits;
+}
+}
+/* Check against the previous initialized values, if any. */
+if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) &&
+(png_ptr->zlib_set_level != level ||
+png_ptr->zlib_set_method != method ||
+png_ptr->zlib_set_window_bits != windowBits ||
+png_ptr->zlib_set_mem_level != memLevel ||
+png_ptr->zlib_set_strategy != strategy))
+{
+if (deflateEnd(&png_ptr->zstream) != Z_OK)
+png_warning(png_ptr, "deflateEnd failed (ignored)");
+png_ptr->flags &= ~PNG_FLAG_ZSTREAM_INITIALIZED;
+}
+/* For safety clear out the input and output pointers (currently zlib
+* doesn't use them on Init, but it might in the future).
+*/
+png_ptr->zstream.next_in = NULL;
+png_ptr->zstream.avail_in = 0;
+png_ptr->zstream.next_out = NULL;
+png_ptr->zstream.avail_out = 0;
+/* Now initialize if required, setting the new parameters, otherwise just
+* to a simple reset to the previous parameters.
+*/
+if (png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED)
+ret = deflateReset(&png_ptr->zstream);
+else
+{
+ret = deflateInit2(&png_ptr->zstream, level, method, windowBits,
+memLevel, strategy);
+if (ret == Z_OK)
+png_ptr->flags |= PNG_FLAG_ZSTREAM_INITIALIZED;
+}
+/* The return code is from either deflateReset or deflateInit2; they have
+* pretty much the same set of error codes.
+*/
+if (ret == Z_OK)
+png_ptr->zowner = owner;
+else
+png_zstream_error(png_ptr, ret);
+return ret;
+}
+}
+/* Clean up (or trim) a linked list of compression buffers. */
+void /* PRIVATE */
+png_free_buffer_list(png_structrp png_ptr, png_compression_bufferp *listp)
+{
+png_compression_bufferp list = *listp;
+if (list != NULL)
+{
+*listp = NULL;
+do
+{
+png_compression_bufferp next = list->next;
+png_free(png_ptr, list);
+list = next;
+}
+while (list != NULL);
+}
+}
+#ifdef PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
+/* This pair of functions encapsulates the operation of (a) compressing a
+* text string, and (b) issuing it later as a series of chunk data writes.
+* The compression_state structure is shared context for these functions
+* set up by the caller to allow access to the relevant local variables.
+*
+* compression_buffer (new in 1.6.0) is just a linked list of zbuffer_size
+* temporary buffers.  From 1.6.0 it is retained in png_struct so that it will
+* be correctly freed in the event of a write error (previous implementations
+* just leaked memory.)
+*/
+typedef struct
+{
+png_const_bytep      input;        /* The uncompressed input data */
+png_alloc_size_t     input_len;    /* Its length */
+png_uint_32          output_len;   /* Final compressed length */
+png_byte             output[1024]; /* First block of output */
+} compression_state;
+static void
+png_text_compress_init(compression_state *comp, png_const_bytep input,
+png_alloc_size_t input_len)
+{
+comp->input = input;
+comp->input_len = input_len;
+comp->output_len = 0;
+}
+/* Compress the data in the compression state input */
+static int
+png_text_compress(png_structrp png_ptr, png_uint_32 chunk_name,
+compression_state *comp, png_uint_32 prefix_len)
+{
+int ret;
+/* To find the length of the output it is necessary to first compress the
+* input, the result is buffered rather than using the two-pass algorithm
+* that is used on the inflate side; deflate is assumed to be slower and a
+* PNG writer is assumed to have more memory available than a PNG reader.
+*
+* IMPLEMENTATION NOTE: the zlib API deflateBound() can be used to find an
+* upper limit on the output size, but it is always bigger than the input
+* size so it is likely to be more efficient to use this linked-list
+* approach.
+*/
+ret = png_deflate_claim(png_ptr, chunk_name, comp->input_len);
+if (ret != Z_OK)
+return ret;
+/* Set up the compression buffers, we need a loop here to avoid overflowing a
+* uInt.  Use ZLIB_IO_MAX to limit the input.  The output is always limited
+* by the output buffer size, so there is no need to check that.  Since this
+* is ANSI-C we know that an 'int', hence a uInt, is always at least 16 bits
+* in size.
+*/
+{
+png_compression_bufferp *end = &png_ptr->zbuffer_list;
+png_alloc_size_t input_len = comp->input_len; /* may be zero! */
+png_uint_32 output_len;
+/* zlib updates these for us: */
+png_ptr->zstream.next_in = PNGZ_INPUT_CAST(comp->input);
+png_ptr->zstream.avail_in = 0; /* Set below */
+png_ptr->zstream.next_out = comp->output;
+png_ptr->zstream.avail_out = (sizeof comp->output);
+output_len = png_ptr->zstream.avail_out;
+do
+{
+uInt avail_in = ZLIB_IO_MAX;
+if (avail_in > input_len)
+avail_in = (uInt)input_len;
+input_len -= avail_in;
+png_ptr->zstream.avail_in = avail_in;
+if (png_ptr->zstream.avail_out == 0)
+{
+png_compression_buffer *next;
+/* Chunk data is limited to 2^31 bytes in length, so the prefix
+* length must be counted here.
+*/
+if (output_len + prefix_len > PNG_UINT_31_MAX)
+{
+ret = Z_MEM_ERROR;
+break;
+}
+/* Need a new (malloc'ed) buffer, but there may be one present
+* already.
+*/
+next = *end;
+if (next == NULL)
+{
+next = png_voidcast(png_compression_bufferp, png_malloc_base
+(png_ptr, PNG_COMPRESSION_BUFFER_SIZE(png_ptr)));
+if (next == NULL)
+{
+ret = Z_MEM_ERROR;
+break;
+}
+/* Link in this buffer (so that it will be freed later) */
+next->next = NULL;
+*end = next;
+}
+png_ptr->zstream.next_out = next->output;
+png_ptr->zstream.avail_out = png_ptr->zbuffer_size;
+output_len += png_ptr->zstream.avail_out;
+/* Move 'end' to the next buffer pointer. */
+end = &next->next;
+}
+/* Compress the data */
+ret = deflate(&png_ptr->zstream,
+input_len > 0 ? Z_NO_FLUSH : Z_FINISH);
+/* Claw back input data that was not consumed (because avail_in is
+* reset above every time round the loop).
+*/
+input_len += png_ptr->zstream.avail_in;
+png_ptr->zstream.avail_in = 0; /* safety */
+}
+while (ret == Z_OK);
+/* There may be some space left in the last output buffer, this needs to
+* be subtracted from output_len.
+*/
+output_len -= png_ptr->zstream.avail_out;
+png_ptr->zstream.avail_out = 0; /* safety */
+comp->output_len = output_len;
+/* Now double check the output length, put in a custom message if it is
+* too long.  Otherwise ensure the z_stream::msg pointer is set to
+* something.
+*/
+if (output_len + prefix_len >= PNG_UINT_31_MAX)
+{
+png_ptr->zstream.msg = PNGZ_MSG_CAST("compressed data too long");
+ret = Z_MEM_ERROR;
+}
+else
+png_zstream_error(png_ptr, ret);
+/* Reset zlib for another zTXt/iTXt or image data */
+png_ptr->zowner = 0;
+/* The only success case is Z_STREAM_END, input_len must be 0, if not this
+* is an internal error.
+*/
+if (ret == Z_STREAM_END && input_len == 0)
+{
+/* Fix up the deflate header, if required */
+optimize_cmf(comp->output, comp->input_len);
+/* But Z_OK is returned, not Z_STREAM_END; this allows the claim
+* function above to return Z_STREAM_END on an error (though it never
+* does in the current versions of zlib.)
+*/
+return Z_OK;
+}
+else
+return ret;
+}
+}
+/* Ship the compressed text out via chunk writes */
+static void
+png_write_compressed_data_out(png_structrp png_ptr, compression_state *comp)
+{
+png_uint_32 output_len = comp->output_len;
+png_const_bytep output = comp->output;
+png_uint_32 avail = (sizeof comp->output);
+png_compression_buffer *next = png_ptr->zbuffer_list;
+for (;;)
+{
+if (avail > output_len)
+avail = output_len;
+png_write_chunk_data(png_ptr, output, avail);
+output_len -= avail;
+if (output_len == 0 || next == NULL)
+break;
+avail = png_ptr->zbuffer_size;
+output = next->output;
+next = next->next;
+}
+/* This is an internal error; 'next' must have been NULL! */
+if (output_len > 0)
+png_error(png_ptr, "error writing ancillary chunked compressed data");
+}
+#endif /* PNG_WRITE_COMPRESSED_TEXT_SUPPORTED */
+#if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_pCAL_SUPPORTED) || \
+defined(PNG_WRITE_iCCP_SUPPORTED) || defined(PNG_WRITE_sPLT_SUPPORTED)
+/* Check that the tEXt or zTXt keyword is valid per PNG 1.0 specification,
+* and if invalid, correct the keyword rather than discarding the entire
+* chunk.  The PNG 1.0 specification requires keywords 1-79 characters in
+* length, forbids leading or trailing whitespace, multiple internal spaces,
+* and the non-break space (0x80) from ISO 8859-1.  Returns keyword length.
+*
+* The 'new_key' buffer must be 80 characters in size (for the keyword plus a
+* trailing '\0').  If this routine returns 0 then there was no keyword, or a
+* valid one could not be generated, and the caller must png_error.
+*/
+static png_uint_32
+png_check_keyword(png_structrp png_ptr, png_const_charp key, png_bytep new_key)
+{
+png_const_charp orig_key = key;
+png_uint_32 key_len = 0;
+int bad_character = 0;
+int space = 1;
+png_debug(1, "in png_check_keyword");
+if (key == NULL)
+{
+*new_key = 0;
+return 0;
+}
+while (*key && key_len < 79)
+{
+png_byte ch = (png_byte)(0xff & *key++);
+if ((ch > 32 && ch <= 126) || (ch >= 161 /*&& ch <= 255*/))
+*new_key++ = ch, ++key_len, space = 0;
+else if (!space)
+{
+/* A space or an invalid character when one wasn't seen immediately
+* before; output just a space.
+*/
+*new_key++ = 32, ++key_len, space = 1;
+/* If the character was not a space then it is invalid. */
+if (ch != 32)
+bad_character = ch;
+}
+else if (!bad_character)
+bad_character = ch; /* just skip it, record the first error */
+}
+if (key_len > 0 && space) /* trailing space */
+{
+--key_len, --new_key;
+if (!bad_character)
+bad_character = 32;
+}
+/* Terminate the keyword */
+*new_key = 0;
+if (key_len == 0)
+return 0;
+/* Try to only output one warning per keyword: */
+if (*key) /* keyword too long */
+png_warning(png_ptr, "keyword truncated");
+else if (bad_character)
+{
+PNG_WARNING_PARAMETERS(p)
+png_warning_parameter(p, 1, orig_key);
+png_warning_parameter_signed(p, 2, PNG_NUMBER_FORMAT_02x, bad_character);
+png_formatted_warning(png_ptr, p, "keyword \"@1\": bad character '0x@2'");
+}
+return key_len;
+}
+#endif
+/* Write the IHDR chunk, and update the png_struct with the necessary
+* information.  Note that the rest of this code depends upon this
+* information being correct.
+*/
+void /* PRIVATE */
+png_write_IHDR(png_structrp png_ptr, png_uint_32 width, png_uint_32 height,
+int bit_depth, int color_type, int compression_type, int filter_type,
+int interlace_type)
+{
+png_byte buf[13]; /* Buffer to store the IHDR info */
+png_debug(1, "in png_write_IHDR");
+/* Check that we have valid input data from the application info */
+switch (color_type)
+{
+case PNG_COLOR_TYPE_GRAY:
+switch (bit_depth)
+{
+case 1:
+case 2:
+case 4:
+case 8:
+#ifdef PNG_WRITE_16BIT_SUPPORTED
+case 16:
+#endif
+png_ptr->channels = 1; break;
+default:
+png_error(png_ptr,
+"Invalid bit depth for grayscale image");
+}
+break;
+case PNG_COLOR_TYPE_RGB:
+#ifdef PNG_WRITE_16BIT_SUPPORTED
+if (bit_depth != 8 && bit_depth != 16)
+#else
+if (bit_depth != 8)
+#endif
+png_error(png_ptr, "Invalid bit depth for RGB image");
+png_ptr->channels = 3;
+break;
+case PNG_COLOR_TYPE_PALETTE:
+switch (bit_depth)
+{
+case 1:
+case 2:
+case 4:
+case 8:
+png_ptr->channels = 1;
+break;
+default:
+png_error(png_ptr, "Invalid bit depth for paletted image");
+}
+break;
+case PNG_COLOR_TYPE_GRAY_ALPHA:
+if (bit_depth != 8 && bit_depth != 16)
+png_error(png_ptr, "Invalid bit depth for grayscale+alpha image");
+png_ptr->channels = 2;
+break;
+case PNG_COLOR_TYPE_RGB_ALPHA:
+#ifdef PNG_WRITE_16BIT_SUPPORTED
+if (bit_depth != 8 && bit_depth != 16)
+#else
+if (bit_depth != 8)
+#endif
+png_error(png_ptr, "Invalid bit depth for RGBA image");
+png_ptr->channels = 4;
+break;
+default:
+png_error(png_ptr, "Invalid image color type specified");
+}
+if (compression_type != PNG_COMPRESSION_TYPE_BASE)
+{
+png_warning(png_ptr, "Invalid compression type specified");
+compression_type = PNG_COMPRESSION_TYPE_BASE;
+}
+/* Write filter_method 64 (intrapixel differencing) only if
+* 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
+* 2. Libpng did not write a PNG signature (this filter_method is only
+*    used in PNG datastreams that are embedded in MNG datastreams) and
+* 3. The application called png_permit_mng_features with a mask that
+*    included PNG_FLAG_MNG_FILTER_64 and
+* 4. The filter_method is 64 and
+* 5. The color_type is RGB or RGBA
+*/
+if (
+#ifdef PNG_MNG_FEATURES_SUPPORTED
+!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
+((png_ptr->mode&PNG_HAVE_PNG_SIGNATURE) == 0) &&
+(color_type == PNG_COLOR_TYPE_RGB ||
+color_type == PNG_COLOR_TYPE_RGB_ALPHA) &&
+(filter_type == PNG_INTRAPIXEL_DIFFERENCING)) &&
+#endif
+filter_type != PNG_FILTER_TYPE_BASE)
+{
+png_warning(png_ptr, "Invalid filter type specified");
+filter_type = PNG_FILTER_TYPE_BASE;
+}
+#ifdef PNG_WRITE_INTERLACING_SUPPORTED
+if (interlace_type != PNG_INTERLACE_NONE &&
+interlace_type != PNG_INTERLACE_ADAM7)
+{
+png_warning(png_ptr, "Invalid interlace type specified");
+interlace_type = PNG_INTERLACE_ADAM7;
+}
+#else
+interlace_type=PNG_INTERLACE_NONE;
+#endif
+/* Save the relevent information */
+png_ptr->bit_depth = (png_byte)bit_depth;
+png_ptr->color_type = (png_byte)color_type;
+png_ptr->interlaced = (png_byte)interlace_type;
+#ifdef PNG_MNG_FEATURES_SUPPORTED
+png_ptr->filter_type = (png_byte)filter_type;
+#endif
+png_ptr->compression_type = (png_byte)compression_type;
+png_ptr->width = width;
+png_ptr->height = height;
+png_ptr->pixel_depth = (png_byte)(bit_depth * png_ptr->channels);
+png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, width);
+/* Set the usr info, so any transformations can modify it */
+png_ptr->usr_width = png_ptr->width;
+png_ptr->usr_bit_depth = png_ptr->bit_depth;
+png_ptr->usr_channels = png_ptr->channels;
+/* Pack the header information into the buffer */
+png_save_uint_32(buf, width);
+png_save_uint_32(buf + 4, height);
+buf[8] = (png_byte)bit_depth;
+buf[9] = (png_byte)color_type;
+buf[10] = (png_byte)compression_type;
+buf[11] = (png_byte)filter_type;
+buf[12] = (png_byte)interlace_type;
+/* Write the chunk */
+png_write_complete_chunk(png_ptr, png_IHDR, buf, (png_size_t)13);
+#ifdef PNG_WRITE_APNG_SUPPORTED
+png_ptr->first_frame_width = width;
+png_ptr->first_frame_height = height;
+#endif
+if (!(png_ptr->do_filter))
+{
+if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
+png_ptr->bit_depth < 8)
+png_ptr->do_filter = PNG_FILTER_NONE;
+else
+png_ptr->do_filter = PNG_ALL_FILTERS;
+}
+png_ptr->mode = PNG_HAVE_IHDR; /* not READY_FOR_ZTXT */
+}
+/* Write the palette.  We are careful not to trust png_color to be in the
+* correct order for PNG, so people can redefine it to any convenient
+* structure.
+*/
+void /* PRIVATE */
+png_write_PLTE(png_structrp png_ptr, png_const_colorp palette,
+png_uint_32 num_pal)
+{
+png_uint_32 i;
+png_const_colorp pal_ptr;
+png_byte buf[3];
+png_debug(1, "in png_write_PLTE");
+if ((
+#ifdef PNG_MNG_FEATURES_SUPPORTED
+!(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE) &&
+#endif
+num_pal == 0) || num_pal > 256)
+{
+if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+{
+png_error(png_ptr, "Invalid number of colors in palette");
+}
+else
+{
+png_warning(png_ptr, "Invalid number of colors in palette");
+return;
+}
+}
+if (!(png_ptr->color_type&PNG_COLOR_MASK_COLOR))
+{
+png_warning(png_ptr,
+"Ignoring request to write a PLTE chunk in grayscale PNG");
+return;
+}
+png_ptr->num_palette = (png_uint_16)num_pal;
+png_debug1(3, "num_palette = %d", png_ptr->num_palette);
+png_write_chunk_header(png_ptr, png_PLTE, (png_uint_32)(num_pal * 3));
+#ifdef PNG_POINTER_INDEXING_SUPPORTED
+for (i = 0, pal_ptr = palette; i < num_pal; i++, pal_ptr++)
+{
+buf[0] = pal_ptr->red;
+buf[1] = pal_ptr->green;
+buf[2] = pal_ptr->blue;
+png_write_chunk_data(png_ptr, buf, (png_size_t)3);
+}
+#else
+/* This is a little slower but some buggy compilers need to do this
+* instead
+*/
+pal_ptr=palette;
+for (i = 0; i < num_pal; i++)
+{
+buf[0] = pal_ptr[i].red;
+buf[1] = pal_ptr[i].green;
+buf[2] = pal_ptr[i].blue;
+png_write_chunk_data(png_ptr, buf, (png_size_t)3);
+}
+#endif
+png_write_chunk_end(png_ptr);
+png_ptr->mode |= PNG_HAVE_PLTE;
+}
+/* This is similar to png_text_compress, above, except that it does not require
+* all of the data at once and, instead of buffering the compressed result,
+* writes it as IDAT chunks.  Unlike png_text_compress it *can* png_error out
+* because it calls the write interface.  As a result it does its own error
+* reporting and does not return an error code.  In the event of error it will
+* just call png_error.  The input data length may exceed 32-bits.  The 'flush'
+* parameter is exactly the same as that to deflate, with the following
+* meanings:
+*
+* Z_NO_FLUSH: normal incremental output of compressed data
+* Z_SYNC_FLUSH: do a SYNC_FLUSH, used by png_write_flush
+* Z_FINISH: this is the end of the input, do a Z_FINISH and clean up
+*
+* The routine manages the acquire and release of the png_ptr->zstream by
+* checking and (at the end) clearing png_ptr->zowner, it does some sanity
+* checks on the 'mode' flags while doing this.
+*/
+void /* PRIVATE */
+png_compress_IDAT(png_structrp png_ptr, png_const_bytep input,
+png_alloc_size_t input_len, int flush)
+{
+if (png_ptr->zowner != png_IDAT)
+{
+/* First time.   Ensure we have a temporary buffer for compression and
+* trim the buffer list if it has more than one entry to free memory.
+* If 'WRITE_COMPRESSED_TEXT' is not set the list will never have been
+* created at this point, but the check here is quick and safe.
+*/
+if (png_ptr->zbuffer_list == NULL)
+{
+png_ptr->zbuffer_list = png_voidcast(png_compression_bufferp,
+png_malloc(png_ptr, PNG_COMPRESSION_BUFFER_SIZE(png_ptr)));
+png_ptr->zbuffer_list->next = NULL;
+}
+else
+png_free_buffer_list(png_ptr, &png_ptr->zbuffer_list->next);
+/* It is a terminal error if we can't claim the zstream. */
+if (png_deflate_claim(png_ptr, png_IDAT, png_image_size(png_ptr)) != Z_OK)
+png_error(png_ptr, png_ptr->zstream.msg);
+/* The output state is maintained in png_ptr->zstream, so it must be
+* initialized here after the claim.
+*/
+png_ptr->zstream.next_out = png_ptr->zbuffer_list->output;
+png_ptr->zstream.avail_out = png_ptr->zbuffer_size;
+}
+/* Now loop reading and writing until all the input is consumed or an error
+* terminates the operation.  The _out values are maintained across calls to
+* this function, but the input must be reset each time.
+*/
+png_ptr->zstream.next_in = PNGZ_INPUT_CAST(input);
+png_ptr->zstream.avail_in = 0; /* set below */
+for (;;)
+{
+int ret;
+/* INPUT: from the row data */
+uInt avail = ZLIB_IO_MAX;
+if (avail > input_len)
+avail = (uInt)input_len; /* safe because of the check */
+png_ptr->zstream.avail_in = avail;
+input_len -= avail;
+ret = deflate(&png_ptr->zstream, input_len > 0 ? Z_NO_FLUSH : flush);
+/* Include as-yet unconsumed input */
+input_len += png_ptr->zstream.avail_in;
+png_ptr->zstream.avail_in = 0;
+/* OUTPUT: write complete IDAT chunks when avail_out drops to zero, note
+* that these two zstream fields are preserved across the calls, therefore
+* there is no need to set these up on entry to the loop.
+*/
+if (png_ptr->zstream.avail_out == 0)
+{
+png_bytep data = png_ptr->zbuffer_list->output;
+uInt size = png_ptr->zbuffer_size;
+/* Write an IDAT containing the data then reset the buffer.  The
+* first IDAT may need deflate header optimization.
+*/
+#        ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
+if (!(png_ptr->mode & PNG_HAVE_IDAT) &&
+png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
+optimize_cmf(data, png_image_size(png_ptr));
+#        endif
+#        ifdef PNG_WRITE_APNG_SUPPORTED
+if (png_ptr->num_frames_written == 0)
+#        endif
+png_write_complete_chunk(png_ptr, png_IDAT, data, size);
+#        ifdef PNG_WRITE_APNG_SUPPORTED
+else
+png_write_fdAT(png_ptr, data, size);
+#        endif /* PNG_WRITE_APNG_SUPPORTED */
+png_ptr->mode |= PNG_HAVE_IDAT;
+png_ptr->zstream.next_out = data;
+png_ptr->zstream.avail_out = size;
+/* For SYNC_FLUSH or FINISH it is essential to keep calling zlib with
+* the same flush parameter until it has finished output, for NO_FLUSH
+* it doesn't matter.
+*/
+if (ret == Z_OK && flush != Z_NO_FLUSH)
+continue;
+}
+/* The order of these checks doesn't matter much; it just effect which
+* possible error might be detected if multiple things go wrong at once.
+*/
+if (ret == Z_OK) /* most likely return code! */
+{
+/* If all the input has been consumed then just return.  If Z_FINISH
+* was used as the flush parameter something has gone wrong if we get
+* here.
+*/
+if (input_len == 0)
+{
+if (flush == Z_FINISH)
+png_error(png_ptr, "Z_OK on Z_FINISH with output space");
+return;
+}
+}
+else if (ret == Z_STREAM_END && flush == Z_FINISH)
+{
+/* This is the end of the IDAT data; any pending output must be
+* flushed.  For small PNG files we may still be at the beginning.
+*/
+png_bytep data = png_ptr->zbuffer_list->output;
+uInt size = png_ptr->zbuffer_size - png_ptr->zstream.avail_out;
+#        ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
+if (!(png_ptr->mode & PNG_HAVE_IDAT) &&
+png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
+optimize_cmf(data, png_image_size(png_ptr));
+#        endif
+#        ifdef PNG_WRITE_APNG_SUPPORTED
+if (png_ptr->num_frames_written == 0)
+#        endif
+png_write_complete_chunk(png_ptr, png_IDAT, data, size);
+#        ifdef PNG_WRITE_APNG_SUPPORTED
+else
+png_write_fdAT(png_ptr, data, size);
+#        endif /* PNG_WRITE_APNG_SUPPORTED */
+png_ptr->zstream.avail_out = 0;
+png_ptr->zstream.next_out = NULL;
+png_ptr->mode |= PNG_HAVE_IDAT | PNG_AFTER_IDAT;
+png_ptr->zowner = 0; /* Release the stream */
+return;
+}
+else
+{
+/* This is an error condition. */
+png_zstream_error(png_ptr, ret);
+png_error(png_ptr, png_ptr->zstream.msg);
+}
+}
+}
+/* Write an IEND chunk */
+void /* PRIVATE */
+png_write_IEND(png_structrp png_ptr)
+{
+png_debug(1, "in png_write_IEND");
+png_write_complete_chunk(png_ptr, png_IEND, NULL, (png_size_t)0);
+png_ptr->mode |= PNG_HAVE_IEND;
+}
+#ifdef PNG_WRITE_gAMA_SUPPORTED
+/* Write a gAMA chunk */
+void /* PRIVATE */
+png_write_gAMA_fixed(png_structrp png_ptr, png_fixed_point file_gamma)
+{
+png_byte buf[4];
+png_debug(1, "in png_write_gAMA");
+/* file_gamma is saved in 1/100,000ths */
+png_save_uint_32(buf, (png_uint_32)file_gamma);
+png_write_complete_chunk(png_ptr, png_gAMA, buf, (png_size_t)4);
+}
+#endif
+#ifdef PNG_WRITE_sRGB_SUPPORTED
+/* Write a sRGB chunk */
+void /* PRIVATE */
+png_write_sRGB(png_structrp png_ptr, int srgb_intent)
+{
+png_byte buf[1];
+png_debug(1, "in png_write_sRGB");
+if (srgb_intent >= PNG_sRGB_INTENT_LAST)
+png_warning(png_ptr,
+"Invalid sRGB rendering intent specified");
+buf[0]=(png_byte)srgb_intent;
+png_write_complete_chunk(png_ptr, png_sRGB, buf, (png_size_t)1);
+}
+#endif
+#ifdef PNG_WRITE_iCCP_SUPPORTED
+/* Write an iCCP chunk */
+void /* PRIVATE */
+png_write_iCCP(png_structrp png_ptr, png_const_charp name,
+png_const_bytep profile)
+{
+png_uint_32 name_len;
+png_uint_32 profile_len;
+png_byte new_name[81]; /* 1 byte for the compression byte */
+compression_state comp;
+png_debug(1, "in png_write_iCCP");
+/* These are all internal problems: the profile should have been checked
+* before when it was stored.
+*/
+if (profile == NULL)
+png_error(png_ptr, "No profile for iCCP chunk"); /* internal error */
+profile_len = png_get_uint_32(profile);
+if (profile_len < 132)
+png_error(png_ptr, "ICC profile too short");
+if (profile_len & 0x03)
+png_error(png_ptr, "ICC profile length invalid (not a multiple of 4)");
+{
+png_uint_32 embedded_profile_len = png_get_uint_32(profile);
+if (profile_len != embedded_profile_len)
+png_error(png_ptr, "Profile length does not match profile");
+}
+name_len = png_check_keyword(png_ptr, name, new_name);
+if (name_len == 0)
+png_error(png_ptr, "iCCP: invalid keyword");
+new_name[++name_len] = PNG_COMPRESSION_TYPE_BASE;
+/* Make sure we include the NULL after the name and the compression type */
+++name_len;
+png_text_compress_init(&comp, profile, profile_len);
+/* Allow for keyword terminator and compression byte */
+if (png_text_compress(png_ptr, png_iCCP, &comp, name_len) != Z_OK)
+png_error(png_ptr, png_ptr->zstream.msg);
+png_write_chunk_header(png_ptr, png_iCCP, name_len + comp.output_len);
+png_write_chunk_data(png_ptr, new_name, name_len);
+png_write_compressed_data_out(png_ptr, &comp);
+png_write_chunk_end(png_ptr);
+}
+#endif
+#ifdef PNG_WRITE_sPLT_SUPPORTED
+/* Write a sPLT chunk */
+void /* PRIVATE */
+png_write_sPLT(png_structrp png_ptr, png_const_sPLT_tp spalette)
+{
+png_uint_32 name_len;
+png_byte new_name[80];
+png_byte entrybuf[10];
+png_size_t entry_size = (spalette->depth == 8 ? 6 : 10);
+png_size_t palette_size = entry_size * spalette->nentries;
+png_sPLT_entryp ep;
+#ifndef PNG_POINTER_INDEXING_SUPPORTED
+int i;
+#endif
+png_debug(1, "in png_write_sPLT");
+name_len = png_check_keyword(png_ptr, spalette->name, new_name);
+if (name_len == 0)
+png_error(png_ptr, "sPLT: invalid keyword");
+/* Make sure we include the NULL after the name */
+png_write_chunk_header(png_ptr, png_sPLT,
+(png_uint_32)(name_len + 2 + palette_size));
+png_write_chunk_data(png_ptr, (png_bytep)new_name,
+(png_size_t)(name_len + 1));
+png_write_chunk_data(png_ptr, &spalette->depth, (png_size_t)1);
+/* Loop through each palette entry, writing appropriately */
+#ifdef PNG_POINTER_INDEXING_SUPPORTED
+for (ep = spalette->entries; ep<spalette->entries + spalette->nentries; ep++)
+{
+if (spalette->depth == 8)
+{
+entrybuf[0] = (png_byte)ep->red;
+entrybuf[1] = (png_byte)ep->green;
+entrybuf[2] = (png_byte)ep->blue;
+entrybuf[3] = (png_byte)ep->alpha;
+png_save_uint_16(entrybuf + 4, ep->frequency);
+}
+else
+{
+png_save_uint_16(entrybuf + 0, ep->red);
+png_save_uint_16(entrybuf + 2, ep->green);
+png_save_uint_16(entrybuf + 4, ep->blue);
+png_save_uint_16(entrybuf + 6, ep->alpha);
+png_save_uint_16(entrybuf + 8, ep->frequency);
+}
+png_write_chunk_data(png_ptr, entrybuf, entry_size);
+}
+#else
+ep=spalette->entries;
+for (i = 0; i>spalette->nentries; i++)
+{
+if (spalette->depth == 8)
+{
+entrybuf[0] = (png_byte)ep[i].red;
+entrybuf[1] = (png_byte)ep[i].green;
+entrybuf[2] = (png_byte)ep[i].blue;
+entrybuf[3] = (png_byte)ep[i].alpha;
+png_save_uint_16(entrybuf + 4, ep[i].frequency);
+}
+else
+{
+png_save_uint_16(entrybuf + 0, ep[i].red);
+png_save_uint_16(entrybuf + 2, ep[i].green);
+png_save_uint_16(entrybuf + 4, ep[i].blue);
+png_save_uint_16(entrybuf + 6, ep[i].alpha);
+png_save_uint_16(entrybuf + 8, ep[i].frequency);
+}
+png_write_chunk_data(png_ptr, entrybuf, entry_size);
+}
+#endif
+png_write_chunk_end(png_ptr);
+}
+#endif
+#ifdef PNG_WRITE_sBIT_SUPPORTED
+/* Write the sBIT chunk */
+void /* PRIVATE */
+png_write_sBIT(png_structrp png_ptr, png_const_color_8p sbit, int color_type)
+{
+png_byte buf[4];
+png_size_t size;
+png_debug(1, "in png_write_sBIT");
+/* Make sure we don't depend upon the order of PNG_COLOR_8 */
+if (color_type & PNG_COLOR_MASK_COLOR)
+{
+png_byte maxbits;
+maxbits = (png_byte)(color_type==PNG_COLOR_TYPE_PALETTE ? 8 :
+png_ptr->usr_bit_depth);
+if (sbit->red == 0 || sbit->red > maxbits ||
+sbit->green == 0 || sbit->green > maxbits ||
+sbit->blue == 0 || sbit->blue > maxbits)
+{
+png_warning(png_ptr, "Invalid sBIT depth specified");
+return;
+}
+buf[0] = sbit->red;
+buf[1] = sbit->green;
+buf[2] = sbit->blue;
+size = 3;
+}
+else
+{
+if (sbit->gray == 0 || sbit->gray > png_ptr->usr_bit_depth)
+{
+png_warning(png_ptr, "Invalid sBIT depth specified");
+return;
+}
+buf[0] = sbit->gray;
+size = 1;
+}
+if (color_type & PNG_COLOR_MASK_ALPHA)
+{
+if (sbit->alpha == 0 || sbit->alpha > png_ptr->usr_bit_depth)
+{
+png_warning(png_ptr, "Invalid sBIT depth specified");
+return;
+}
+buf[size++] = sbit->alpha;
+}
+png_write_complete_chunk(png_ptr, png_sBIT, buf, size);
+}
+#endif
+#ifdef PNG_WRITE_cHRM_SUPPORTED
+/* Write the cHRM chunk */
+void /* PRIVATE */
+png_write_cHRM_fixed(png_structrp png_ptr, const png_xy *xy)
+{
+png_byte buf[32];
+png_debug(1, "in png_write_cHRM");
+/* Each value is saved in 1/100,000ths */
+png_save_int_32(buf,      xy->whitex);
+png_save_int_32(buf +  4, xy->whitey);
+png_save_int_32(buf +  8, xy->redx);
+png_save_int_32(buf + 12, xy->redy);
+png_save_int_32(buf + 16, xy->greenx);
+png_save_int_32(buf + 20, xy->greeny);
+png_save_int_32(buf + 24, xy->bluex);
+png_save_int_32(buf + 28, xy->bluey);
+png_write_complete_chunk(png_ptr, png_cHRM, buf, 32);
+}
+#endif
+#ifdef PNG_WRITE_tRNS_SUPPORTED
+/* Write the tRNS chunk */
+void /* PRIVATE */
+png_write_tRNS(png_structrp png_ptr, png_const_bytep trans_alpha,
+png_const_color_16p tran, int num_trans, int color_type)
+{
+png_byte buf[6];
+png_debug(1, "in png_write_tRNS");
+if (color_type == PNG_COLOR_TYPE_PALETTE)
+{
+if (num_trans <= 0 || num_trans > (int)png_ptr->num_palette)
+{
+png_app_warning(png_ptr,
+"Invalid number of transparent colors specified");
+return;
+}
+/* Write the chunk out as it is */
+png_write_complete_chunk(png_ptr, png_tRNS, trans_alpha,
+(png_size_t)num_trans);
+}
+else if (color_type == PNG_COLOR_TYPE_GRAY)
+{
+/* One 16 bit value */
+if (tran->gray >= (1 << png_ptr->bit_depth))
+{
+png_app_warning(png_ptr,
+"Ignoring attempt to write tRNS chunk out-of-range for bit_depth");
+return;
+}
+png_save_uint_16(buf, tran->gray);
+png_write_complete_chunk(png_ptr, png_tRNS, buf, (png_size_t)2);
+}
+else if (color_type == PNG_COLOR_TYPE_RGB)
+{
+/* Three 16 bit values */
+png_save_uint_16(buf, tran->red);
+png_save_uint_16(buf + 2, tran->green);
+png_save_uint_16(buf + 4, tran->blue);
+#ifdef PNG_WRITE_16BIT_SUPPORTED
+if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]))
+#else
+if (buf[0] | buf[2] | buf[4])
+#endif
+{
+png_app_warning(png_ptr,
+"Ignoring attempt to write 16-bit tRNS chunk when bit_depth is 8");
+return;
+}
+png_write_complete_chunk(png_ptr, png_tRNS, buf, (png_size_t)6);
+}
+else
+{
+png_app_warning(png_ptr, "Can't write tRNS with an alpha channel");
+}
+}
+#endif
+#ifdef PNG_WRITE_bKGD_SUPPORTED
+/* Write the background chunk */
+void /* PRIVATE */
+png_write_bKGD(png_structrp png_ptr, png_const_color_16p back, int color_type)
+{
+png_byte buf[6];
+png_debug(1, "in png_write_bKGD");
+if (color_type == PNG_COLOR_TYPE_PALETTE)
+{
+if (
+#ifdef PNG_MNG_FEATURES_SUPPORTED
+(png_ptr->num_palette ||
+(!(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE))) &&
+#endif
+back->index >= png_ptr->num_palette)
+{
+png_warning(png_ptr, "Invalid background palette index");
+return;
+}
+buf[0] = back->index;
+png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)1);
+}
+else if (color_type & PNG_COLOR_MASK_COLOR)
+{
+png_save_uint_16(buf, back->red);
+png_save_uint_16(buf + 2, back->green);
+png_save_uint_16(buf + 4, back->blue);
+#ifdef PNG_WRITE_16BIT_SUPPORTED
+if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]))
+#else
+if (buf[0] | buf[2] | buf[4])
+#endif
+{
+png_warning(png_ptr,
+"Ignoring attempt to write 16-bit bKGD chunk when bit_depth is 8");
+return;
+}
+png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)6);
+}
+else
+{
+if (back->gray >= (1 << png_ptr->bit_depth))
+{
+png_warning(png_ptr,
+"Ignoring attempt to write bKGD chunk out-of-range for bit_depth");
+return;
+}
+png_save_uint_16(buf, back->gray);
+png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)2);
+}
+}
+#endif
+#ifdef PNG_WRITE_hIST_SUPPORTED
+/* Write the histogram */
+void /* PRIVATE */
+png_write_hIST(png_structrp png_ptr, png_const_uint_16p hist, int num_hist)
+{
+int i;
+png_byte buf[3];
+png_debug(1, "in png_write_hIST");
+if (num_hist > (int)png_ptr->num_palette)
+{
+png_debug2(3, "num_hist = %d, num_palette = %d", num_hist,
+png_ptr->num_palette);
+png_warning(png_ptr, "Invalid number of histogram entries specified");
+return;
+}
+png_write_chunk_header(png_ptr, png_hIST, (png_uint_32)(num_hist * 2));
+for (i = 0; i < num_hist; i++)
+{
+png_save_uint_16(buf, hist[i]);
+png_write_chunk_data(png_ptr, buf, (png_size_t)2);
+}
+png_write_chunk_end(png_ptr);
+}
+#endif
+#ifdef PNG_WRITE_tEXt_SUPPORTED
+/* Write a tEXt chunk */
+void /* PRIVATE */
+png_write_tEXt(png_structrp png_ptr, png_const_charp key, png_const_charp text,
+png_size_t text_len)
+{
+png_uint_32 key_len;
+png_byte new_key[80];
+png_debug(1, "in png_write_tEXt");
+key_len = png_check_keyword(png_ptr, key, new_key);
+if (key_len == 0)
+png_error(png_ptr, "tEXt: invalid keyword");
+if (text == NULL || *text == '\0')
+text_len = 0;
+else
+text_len = strlen(text);
+if (text_len > PNG_UINT_31_MAX - (key_len+1))
+png_error(png_ptr, "tEXt: text too long");
+/* Make sure we include the 0 after the key */
+png_write_chunk_header(png_ptr, png_tEXt,
+(png_uint_32)/*checked above*/(key_len + text_len + 1));
+/*
+* We leave it to the application to meet PNG-1.0 requirements on the
+* contents of the text.  PNG-1.0 through PNG-1.2 discourage the use of
+* any non-Latin-1 characters except for NEWLINE.  ISO PNG will forbid them.
+* The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
+*/
+png_write_chunk_data(png_ptr, new_key, key_len + 1);
+if (text_len)
+png_write_chunk_data(png_ptr, (png_const_bytep)text, text_len);
+png_write_chunk_end(png_ptr);
+}
+#endif
+#ifdef PNG_WRITE_zTXt_SUPPORTED
+/* Write a compressed text chunk */
+void /* PRIVATE */
+png_write_zTXt(png_structrp png_ptr, png_const_charp key, png_const_charp text,
+png_size_t text_len, int compression)
+{
+png_uint_32 key_len;
+png_byte new_key[81];
+compression_state comp;
+png_debug(1, "in png_write_zTXt");
+PNG_UNUSED(text_len) /* Always use strlen */
+if (compression == PNG_TEXT_COMPRESSION_NONE)
+{
+png_write_tEXt(png_ptr, key, text, 0);
+return;
+}
+if (compression != PNG_TEXT_COMPRESSION_zTXt)
+png_error(png_ptr, "zTXt: invalid compression type");
+key_len = png_check_keyword(png_ptr, key, new_key);
+if (key_len == 0)
+png_error(png_ptr, "zTXt: invalid keyword");
+/* Add the compression method and 1 for the keyword separator. */
+new_key[++key_len] = PNG_COMPRESSION_TYPE_BASE;
+++key_len;
+/* Compute the compressed data; do it now for the length */
+png_text_compress_init(&comp, (png_const_bytep)text,
+text == NULL ? 0 : strlen(text));
+if (png_text_compress(png_ptr, png_zTXt, &comp, key_len) != Z_OK)
+png_error(png_ptr, png_ptr->zstream.msg);
+/* Write start of chunk */
+png_write_chunk_header(png_ptr, png_zTXt, key_len + comp.output_len);
+/* Write key */
+png_write_chunk_data(png_ptr, new_key, key_len);
+/* Write the compressed data */
+png_write_compressed_data_out(png_ptr, &comp);
+/* Close the chunk */
+png_write_chunk_end(png_ptr);
+}
+#endif
+#ifdef PNG_WRITE_iTXt_SUPPORTED
+/* Write an iTXt chunk */
+void /* PRIVATE */
+png_write_iTXt(png_structrp png_ptr, int compression, png_const_charp key,
+png_const_charp lang, png_const_charp lang_key, png_const_charp text)
+{
+png_uint_32 key_len, prefix_len;
+png_size_t lang_len, lang_key_len;
+png_byte new_key[82];
+compression_state comp;
+png_debug(1, "in png_write_iTXt");
+key_len = png_check_keyword(png_ptr, key, new_key);
+if (key_len == 0)
+png_error(png_ptr, "iTXt: invalid keyword");
+/* Set the compression flag */
+switch (compression)
+{
+case PNG_ITXT_COMPRESSION_NONE:
+case PNG_TEXT_COMPRESSION_NONE:
+compression = new_key[++key_len] = 0; /* no compression */
+break;
+case PNG_TEXT_COMPRESSION_zTXt:
+case PNG_ITXT_COMPRESSION_zTXt:
+compression = new_key[++key_len] = 1; /* compressed */
+break;
+default:
+png_error(png_ptr, "iTXt: invalid compression");
+}
+new_key[++key_len] = PNG_COMPRESSION_TYPE_BASE;
+++key_len; /* for the keywod separator */
+/* We leave it to the application to meet PNG-1.0 requirements on the
+* contents of the text.  PNG-1.0 through PNG-1.2 discourage the use of
+* any non-Latin-1 characters except for NEWLINE.  ISO PNG, however,
+* specifies that the text is UTF-8 and this really doesn't require any
+* checking.
+*
+* The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
+*
+* TODO: validate the language tag correctly (see the spec.)
+*/
+if (lang == NULL) lang = ""; /* empty language is valid */
+lang_len = strlen(lang)+1;
+if (lang_key == NULL) lang_key = ""; /* may be empty */
+lang_key_len = strlen(lang_key)+1;
+if (text == NULL) text = ""; /* may be empty */
+prefix_len = key_len;
+if (lang_len > PNG_UINT_31_MAX-prefix_len)
+prefix_len = PNG_UINT_31_MAX;
+else
+prefix_len = (png_uint_32)(prefix_len + lang_len);
+if (lang_key_len > PNG_UINT_31_MAX-prefix_len)
+prefix_len = PNG_UINT_31_MAX;
+else
+prefix_len = (png_uint_32)(prefix_len + lang_key_len);
+png_text_compress_init(&comp, (png_const_bytep)text, strlen(text));
+if (compression)
+{
+if (png_text_compress(png_ptr, png_iTXt, &comp, prefix_len) != Z_OK)
+png_error(png_ptr, png_ptr->zstream.msg);
+}
+else
+{
+if (comp.input_len > PNG_UINT_31_MAX-prefix_len)
+png_error(png_ptr, "iTXt: uncompressed text too long");
+/* So the string will fit in a chunk: */
+comp.output_len = (png_uint_32)/*SAFE*/comp.input_len;
+}
+png_write_chunk_header(png_ptr, png_iTXt, comp.output_len + prefix_len);
+png_write_chunk_data(png_ptr, new_key, key_len);
+png_write_chunk_data(png_ptr, (png_const_bytep)lang, lang_len);
+png_write_chunk_data(png_ptr, (png_const_bytep)lang_key, lang_key_len);
+if (compression)
+png_write_compressed_data_out(png_ptr, &comp);
+else
+png_write_chunk_data(png_ptr, (png_const_bytep)text, comp.input_len);
+png_write_chunk_end(png_ptr);
+}
+#endif
+#ifdef PNG_WRITE_oFFs_SUPPORTED
+/* Write the oFFs chunk */
+void /* PRIVATE */
+png_write_oFFs(png_structrp png_ptr, png_int_32 x_offset, png_int_32 y_offset,
+int unit_type)
+{
+png_byte buf[9];
+png_debug(1, "in png_write_oFFs");
+if (unit_type >= PNG_OFFSET_LAST)
+png_warning(png_ptr, "Unrecognized unit type for oFFs chunk");
+png_save_int_32(buf, x_offset);
+png_save_int_32(buf + 4, y_offset);
+buf[8] = (png_byte)unit_type;
+png_write_complete_chunk(png_ptr, png_oFFs, buf, (png_size_t)9);
+}
+#endif
+#ifdef PNG_WRITE_pCAL_SUPPORTED
+/* Write the pCAL chunk (described in the PNG extensions document) */
+void /* PRIVATE */
+png_write_pCAL(png_structrp png_ptr, png_charp purpose, png_int_32 X0,
+png_int_32 X1, int type, int nparams, png_const_charp units,
+png_charpp params)
+{
+png_uint_32 purpose_len;
+png_size_t units_len, total_len;
+png_size_tp params_len;
+png_byte buf[10];
+png_byte new_purpose[80];
+int i;
+png_debug1(1, "in png_write_pCAL (%d parameters)", nparams);
+if (type >= PNG_EQUATION_LAST)
+png_error(png_ptr, "Unrecognized equation type for pCAL chunk");
+purpose_len = png_check_keyword(png_ptr, purpose, new_purpose);
+if (purpose_len == 0)
+png_error(png_ptr, "pCAL: invalid keyword");
+++purpose_len; /* terminator */
+png_debug1(3, "pCAL purpose length = %d", (int)purpose_len);
+units_len = strlen(units) + (nparams == 0 ? 0 : 1);
+png_debug1(3, "pCAL units length = %d", (int)units_len);
+total_len = purpose_len + units_len + 10;
+params_len = (png_size_tp)png_malloc(png_ptr,
+(png_alloc_size_t)(nparams * (sizeof (png_size_t))));
+/* Find the length of each parameter, making sure we don't count the
+* null terminator for the last parameter.
+*/
+for (i = 0; i < nparams; i++)
+{
+params_len[i] = strlen(params[i]) + (i == nparams - 1 ? 0 : 1);
+png_debug2(3, "pCAL parameter %d length = %lu", i,
+(unsigned long)params_len[i]);
+total_len += params_len[i];
+}
+png_debug1(3, "pCAL total length = %d", (int)total_len);
+png_write_chunk_header(png_ptr, png_pCAL, (png_uint_32)total_len);
+png_write_chunk_data(png_ptr, new_purpose, purpose_len);
+png_save_int_32(buf, X0);
+png_save_int_32(buf + 4, X1);
+buf[8] = (png_byte)type;
+buf[9] = (png_byte)nparams;
+png_write_chunk_data(png_ptr, buf, (png_size_t)10);
+png_write_chunk_data(png_ptr, (png_const_bytep)units, (png_size_t)units_len);
+for (i = 0; i < nparams; i++)
+{
+png_write_chunk_data(png_ptr, (png_const_bytep)params[i], params_len[i]);
+}
+png_free(png_ptr, params_len);
+png_write_chunk_end(png_ptr);
+}
+#endif
+#ifdef PNG_WRITE_sCAL_SUPPORTED
+/* Write the sCAL chunk */
+void /* PRIVATE */
+png_write_sCAL_s(png_structrp png_ptr, int unit, png_const_charp width,
+png_const_charp height)
+{
+png_byte buf[64];
+png_size_t wlen, hlen, total_len;
+png_debug(1, "in png_write_sCAL_s");
+wlen = strlen(width);
+hlen = strlen(height);
+total_len = wlen + hlen + 2;
+if (total_len > 64)
+{
+png_warning(png_ptr, "Can't write sCAL (buffer too small)");
+return;
+}
+buf[0] = (png_byte)unit;
+memcpy(buf + 1, width, wlen + 1);      /* Append the '\0' here */
+memcpy(buf + wlen + 2, height, hlen);  /* Do NOT append the '\0' here */
+png_debug1(3, "sCAL total length = %u", (unsigned int)total_len);
+png_write_complete_chunk(png_ptr, png_sCAL, buf, total_len);
+}
+#endif
+#ifdef PNG_WRITE_pHYs_SUPPORTED
+/* Write the pHYs chunk */
+void /* PRIVATE */
+png_write_pHYs(png_structrp png_ptr, png_uint_32 x_pixels_per_unit,
+png_uint_32 y_pixels_per_unit,
+int unit_type)
+{
+png_byte buf[9];
+png_debug(1, "in png_write_pHYs");
+if (unit_type >= PNG_RESOLUTION_LAST)
+png_warning(png_ptr, "Unrecognized unit type for pHYs chunk");
+png_save_uint_32(buf, x_pixels_per_unit);
+png_save_uint_32(buf + 4, y_pixels_per_unit);
+buf[8] = (png_byte)unit_type;
+png_write_complete_chunk(png_ptr, png_pHYs, buf, (png_size_t)9);
+}
+#endif
+#ifdef PNG_WRITE_tIME_SUPPORTED
+/* Write the tIME chunk.  Use either png_convert_from_struct_tm()
+* or png_convert_from_time_t(), or fill in the structure yourself.
+*/
+void /* PRIVATE */
+png_write_tIME(png_structrp png_ptr, png_const_timep mod_time)
+{
+png_byte buf[7];
+png_debug(1, "in png_write_tIME");
+if (mod_time->month  > 12 || mod_time->month  < 1 ||
+mod_time->day    > 31 || mod_time->day    < 1 ||
+mod_time->hour   > 23 || mod_time->second > 60)
+{
+png_warning(png_ptr, "Invalid time specified for tIME chunk");
+return;
+}
+png_save_uint_16(buf, mod_time->year);
+buf[2] = mod_time->month;
+buf[3] = mod_time->day;
+buf[4] = mod_time->hour;
+buf[5] = mod_time->minute;
+buf[6] = mod_time->second;
+png_write_complete_chunk(png_ptr, png_tIME, buf, (png_size_t)7);
+}
+#endif
+#ifdef PNG_WRITE_APNG_SUPPORTED
+void /* PRIVATE */
+png_write_acTL(png_structp png_ptr,
+png_uint_32 num_frames, png_uint_32 num_plays)
+{
+png_byte buf[8];
+png_debug(1, "in png_write_acTL");
+png_ptr->num_frames_to_write = num_frames;
+if (png_ptr->apng_flags & PNG_FIRST_FRAME_HIDDEN)
+num_frames--;
+png_save_uint_32(buf, num_frames);
+png_save_uint_32(buf + 4, num_plays);
+png_write_complete_chunk(png_ptr, png_acTL, buf, (png_size_t)8);
+}
+void /* PRIVATE */
+png_write_fcTL(png_structp png_ptr, png_uint_32 width, png_uint_32 height,
+png_uint_32 x_offset, png_uint_32 y_offset,
+png_uint_16 delay_num, png_uint_16 delay_den, png_byte dispose_op,
+png_byte blend_op)
+{
+png_byte buf[26];
+png_debug(1, "in png_write_fcTL");
+if (png_ptr->num_frames_written == 0 && (x_offset != 0 || y_offset != 0))
+png_error(png_ptr, "x and/or y offset for the first frame aren't 0");
+if (png_ptr->num_frames_written == 0 &&
+(width != png_ptr->first_frame_width ||
+height != png_ptr->first_frame_height))
+png_error(png_ptr, "width and/or height in the first frame's fcTL "
+"don't match the ones in IHDR");
+/* more error checking */
+png_ensure_fcTL_is_valid(png_ptr, width, height, x_offset, y_offset,
+delay_num, delay_den, dispose_op, blend_op);
+png_save_uint_32(buf, png_ptr->next_seq_num);
+png_save_uint_32(buf + 4, width);
+png_save_uint_32(buf + 8, height);
+png_save_uint_32(buf + 12, x_offset);
+png_save_uint_32(buf + 16, y_offset);
+png_save_uint_16(buf + 20, delay_num);
+png_save_uint_16(buf + 22, delay_den);
+buf[24] = dispose_op;
+buf[25] = blend_op;
+png_write_complete_chunk(png_ptr, png_fcTL, buf, (png_size_t)26);
+png_ptr->next_seq_num++;
+}
+void /* PRIVATE */
+png_write_fdAT(png_structp png_ptr,
+png_const_bytep data, png_size_t length)
+{
+png_byte buf[4];
+png_write_chunk_header(png_ptr, png_fdAT, (png_uint_32)(4 + length));
+png_save_uint_32(buf, png_ptr->next_seq_num);
+png_write_chunk_data(png_ptr, buf, 4);
+png_write_chunk_data(png_ptr, data, length);
+png_write_chunk_end(png_ptr);
+png_ptr->next_seq_num++;
+}
+#endif /* PNG_WRITE_APNG_SUPPORTED */
+/* Initializes the row writing capability of libpng */
+void /* PRIVATE */
+png_write_start_row(png_structrp png_ptr)
+{
+#ifdef PNG_WRITE_INTERLACING_SUPPORTED
+/* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
+/* Start of interlace block */
+static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+/* Offset to next interlace block */
+static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+/* Start of interlace block in the y direction */
+static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+/* Offset to next interlace block in the y direction */
+static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+#endif
+png_alloc_size_t buf_size;
+int usr_pixel_depth;
+png_debug(1, "in png_write_start_row");
+usr_pixel_depth = png_ptr->usr_channels * png_ptr->usr_bit_depth;
+buf_size = PNG_ROWBYTES(usr_pixel_depth, png_ptr->width) + 1;
+/* 1.5.6: added to allow checking in the row write code. */
+png_ptr->transformed_pixel_depth = png_ptr->pixel_depth;
+png_ptr->maximum_pixel_depth = (png_byte)usr_pixel_depth;
+/* Set up row buffer */
+png_ptr->row_buf = (png_bytep)png_malloc(png_ptr, buf_size);
+png_ptr->row_buf[0] = PNG_FILTER_VALUE_NONE;
+#ifdef PNG_WRITE_FILTER_SUPPORTED
+/* Set up filtering buffer, if using this filter */
+if (png_ptr->do_filter & PNG_FILTER_SUB)
+{
+png_ptr->sub_row = (png_bytep)png_malloc(png_ptr, png_ptr->rowbytes + 1);
+png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
+}
+/* We only need to keep the previous row if we are using one of these. */
+if (png_ptr->do_filter & (PNG_FILTER_AVG | PNG_FILTER_UP | PNG_FILTER_PAETH))
+{
+/* Set up previous row buffer */
+png_ptr->prev_row = (png_bytep)png_calloc(png_ptr, buf_size);
+if (png_ptr->do_filter & PNG_FILTER_UP)
+{
+png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
+png_ptr->rowbytes + 1);
+png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
+}
+if (png_ptr->do_filter & PNG_FILTER_AVG)
+{
+png_ptr->avg_row = (png_bytep)png_malloc(png_ptr,
+png_ptr->rowbytes + 1);
+png_ptr->avg_row[0] = PNG_FILTER_VALUE_AVG;
+}
+if (png_ptr->do_filter & PNG_FILTER_PAETH)
+{
+png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
+png_ptr->rowbytes + 1);
+png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
+}
+}
+#endif /* PNG_WRITE_FILTER_SUPPORTED */
+#ifdef PNG_WRITE_INTERLACING_SUPPORTED
+/* If interlaced, we need to set up width and height of pass */
+if (png_ptr->interlaced)
+{
+if (!(png_ptr->transformations & PNG_INTERLACE))
+{
+png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
+png_pass_ystart[0]) / png_pass_yinc[0];
+png_ptr->usr_width = (png_ptr->width + png_pass_inc[0] - 1 -
+png_pass_start[0]) / png_pass_inc[0];
+}
+else
+{
+png_ptr->num_rows = png_ptr->height;
+png_ptr->usr_width = png_ptr->width;
+}
+}
+else
+#endif
+{
+png_ptr->num_rows = png_ptr->height;
+png_ptr->usr_width = png_ptr->width;
+}
+}
+/* Internal use only.  Called when finished processing a row of data. */
+void /* PRIVATE */
+png_write_finish_row(png_structrp png_ptr)
+{
+#ifdef PNG_WRITE_INTERLACING_SUPPORTED
+/* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
+/* Start of interlace block */
+static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+/* Offset to next interlace block */
+static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+/* Start of interlace block in the y direction */
+static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+/* Offset to next interlace block in the y direction */
+static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+#endif
+png_debug(1, "in png_write_finish_row");
+/* Next row */
+png_ptr->row_number++;
+/* See if we are done */
+if (png_ptr->row_number < png_ptr->num_rows)
+return;
+#ifdef PNG_WRITE_INTERLACING_SUPPORTED
+/* If interlaced, go to next pass */
+if (png_ptr->interlaced)
+{
+png_ptr->row_number = 0;
+if (png_ptr->transformations & PNG_INTERLACE)
+{
+png_ptr->pass++;
+}
+else
+{
+/* Loop until we find a non-zero width or height pass */
+do
+{
+png_ptr->pass++;
+if (png_ptr->pass >= 7)
+break;
+png_ptr->usr_width = (png_ptr->width +
+png_pass_inc[png_ptr->pass] - 1 -
+png_pass_start[png_ptr->pass]) /
+png_pass_inc[png_ptr->pass];
+png_ptr->num_rows = (png_ptr->height +
+png_pass_yinc[png_ptr->pass] - 1 -
+png_pass_ystart[png_ptr->pass]) /
+png_pass_yinc[png_ptr->pass];
+if (png_ptr->transformations & PNG_INTERLACE)
+break;
+} while (png_ptr->usr_width == 0 || png_ptr->num_rows == 0);
+}
+/* Reset the row above the image for the next pass */
+if (png_ptr->pass < 7)
+{
+if (png_ptr->prev_row != NULL)
+memset(png_ptr->prev_row, 0,
+(png_size_t)(PNG_ROWBYTES(png_ptr->usr_channels*
+png_ptr->usr_bit_depth, png_ptr->width)) + 1);
+return;
+}
+}
+#endif
+/* If we get here, we've just written the last row, so we need
+to flush the compressor */
+png_compress_IDAT(png_ptr, NULL, 0, Z_FINISH);
+}
+#ifdef PNG_WRITE_INTERLACING_SUPPORTED
+/* Pick out the correct pixels for the interlace pass.
+* The basic idea here is to go through the row with a source
+* pointer and a destination pointer (sp and dp), and copy the
+* correct pixels for the pass.  As the row gets compacted,
+* sp will always be >= dp, so we should never overwrite anything.
+* See the default: case for the easiest code to understand.
+*/
+void /* PRIVATE */
+png_do_write_interlace(png_row_infop row_info, png_bytep row, int pass)
+{
+/* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
+/* Start of interlace block */
+static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+/* Offset to next interlace block */
+static PNG_CONST png_byte  png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+png_debug(1, "in png_do_write_interlace");
+/* We don't have to do anything on the last pass (6) */
+if (pass < 6)
+{
+/* Each pixel depth is handled separately */
+switch (row_info->pixel_depth)
+{
+case 1:
+{
+png_bytep sp;
+png_bytep dp;
+int shift;
+int d;
+int value;
+png_uint_32 i;
+png_uint_32 row_width = row_info->width;
+dp = row;
+d = 0;
+shift = 7;
+for (i = png_pass_start[pass]; i < row_width;
+i += png_pass_inc[pass])
+{
+sp = row + (png_size_t)(i >> 3);
+value = (int)(*sp >> (7 - (int)(i & 0x07))) & 0x01;
+d |= (value << shift);
+if (shift == 0)
+{
+shift = 7;
+*dp++ = (png_byte)d;
+d = 0;
+}
+else
+shift--;
+}
+if (shift != 7)
+*dp = (png_byte)d;
+break;
+}
+case 2:
+{
+png_bytep sp;
+png_bytep dp;
+int shift;
+int d;
+int value;
+png_uint_32 i;
+png_uint_32 row_width = row_info->width;
+dp = row;
+shift = 6;
+d = 0;
+for (i = png_pass_start[pass]; i < row_width;
+i += png_pass_inc[pass])
+{
+sp = row + (png_size_t)(i >> 2);
+value = (*sp >> ((3 - (int)(i & 0x03)) << 1)) & 0x03;
+d |= (value << shift);
+if (shift == 0)
+{
+shift = 6;
+*dp++ = (png_byte)d;
+d = 0;
+}
+else
+shift -= 2;
+}
+if (shift != 6)
+*dp = (png_byte)d;
+break;
+}
+case 4:
+{
+png_bytep sp;
+png_bytep dp;
+int shift;
+int d;
+int value;
+png_uint_32 i;
+png_uint_32 row_width = row_info->width;
+dp = row;
+shift = 4;
+d = 0;
+for (i = png_pass_start[pass]; i < row_width;
+i += png_pass_inc[pass])
+{
+sp = row + (png_size_t)(i >> 1);
+value = (*sp >> ((1 - (int)(i & 0x01)) << 2)) & 0x0f;
+d |= (value << shift);
+if (shift == 0)
+{
+shift = 4;
+*dp++ = (png_byte)d;
+d = 0;
+}
+else
+shift -= 4;
+}
+if (shift != 4)
+*dp = (png_byte)d;
+break;
+}
+default:
+{
+png_bytep sp;
+png_bytep dp;
+png_uint_32 i;
+png_uint_32 row_width = row_info->width;
+png_size_t pixel_bytes;
+/* Start at the beginning */
+dp = row;
+/* Find out how many bytes each pixel takes up */
+pixel_bytes = (row_info->pixel_depth >> 3);
+/* Loop through the row, only looking at the pixels that matter */
+for (i = png_pass_start[pass]; i < row_width;
+i += png_pass_inc[pass])
+{
+/* Find out where the original pixel is */
+sp = row + (png_size_t)i * pixel_bytes;
+/* Move the pixel */
+if (dp != sp)
+memcpy(dp, sp, pixel_bytes);
+/* Next pixel */
+dp += pixel_bytes;
+}
+break;
+}
+}
+/* Set new row width */
+row_info->width = (row_info->width +
+png_pass_inc[pass] - 1 -
+png_pass_start[pass]) /
+png_pass_inc[pass];
+row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
+row_info->width);
+}
+}
+#endif
+/* This filters the row, chooses which filter to use, if it has not already
+* been specified by the application, and then writes the row out with the
+* chosen filter.
+*/
+static void
+png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
+png_size_t row_bytes);
+#define PNG_MAXSUM (((png_uint_32)(-1)) >> 1)
+#define PNG_HISHIFT 10
+#define PNG_LOMASK ((png_uint_32)0xffffL)
+#define PNG_HIMASK ((png_uint_32)(~PNG_LOMASK >> PNG_HISHIFT))
+void /* PRIVATE */
+png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
+{
+png_bytep best_row;
+#ifdef PNG_WRITE_FILTER_SUPPORTED
+png_bytep prev_row, row_buf;
+png_uint_32 mins, bpp;
+png_byte filter_to_do = png_ptr->do_filter;
+png_size_t row_bytes = row_info->rowbytes;
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+int num_p_filters = png_ptr->num_prev_filters;
+#endif
+png_debug(1, "in png_write_find_filter");
+#ifndef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+if (png_ptr->row_number == 0 && filter_to_do == PNG_ALL_FILTERS)
+{
+/* These will never be selected so we need not test them. */
+filter_to_do &= ~(PNG_FILTER_UP | PNG_FILTER_PAETH);
+}
+#endif
+/* Find out how many bytes offset each pixel is */
+bpp = (row_info->pixel_depth + 7) >> 3;
+prev_row = png_ptr->prev_row;
+#endif
+best_row = png_ptr->row_buf;
+#ifdef PNG_WRITE_FILTER_SUPPORTED
+row_buf = best_row;
+mins = PNG_MAXSUM;
+/* The prediction method we use is to find which method provides the
+* smallest value when summing the absolute values of the distances
+* from zero, using anything >= 128 as negative numbers.  This is known
+* as the "minimum sum of absolute differences" heuristic.  Other
+* heuristics are the "weighted minimum sum of absolute differences"
+* (experimental and can in theory improve compression), and the "zlib
+* predictive" method (not implemented yet), which does test compressions
+* of lines using different filter methods, and then chooses the
+* (series of) filter(s) that give minimum compressed data size (VERY
+* computationally expensive).
+*
+* GRR 980525:  consider also
+*
+*   (1) minimum sum of absolute differences from running average (i.e.,
+*       keep running sum of non-absolute differences & count of bytes)
+*       [track dispersion, too?  restart average if dispersion too large?]
+*
+*  (1b) minimum sum of absolute differences from sliding average, probably
+*       with window size <= deflate window (usually 32K)
+*
+*   (2) minimum sum of squared differences from zero or running average
+*       (i.e., ~ root-mean-square approach)
+*/
+/* We don't need to test the 'no filter' case if this is the only filter
+* that has been chosen, as it doesn't actually do anything to the data.
+*/
+if ((filter_to_do & PNG_FILTER_NONE) && filter_to_do != PNG_FILTER_NONE)
+{
+png_bytep rp;
+png_uint_32 sum = 0;
+png_size_t i;
+int v;
+for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
+{
+v = *rp;
+sum += (v < 128) ? v : 256 - v;
+}
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+{
+png_uint_32 sumhi, sumlo;
+int j;
+sumlo = sum & PNG_LOMASK;
+sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK; /* Gives us some footroom */
+/* Reduce the sum if we match any of the previous rows */
+for (j = 0; j < num_p_filters; j++)
+{
+if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
+{
+sumlo = (sumlo * png_ptr->filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+sumhi = (sumhi * png_ptr->filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+}
+}
+/* Factor in the cost of this filter (this is here for completeness,
+* but it makes no sense to have a "cost" for the NONE filter, as
+* it has the minimum possible computational cost - none).
+*/
+sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
+PNG_COST_SHIFT;
+sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_NONE]) >>
+PNG_COST_SHIFT;
+if (sumhi > PNG_HIMASK)
+sum = PNG_MAXSUM;
+else
+sum = (sumhi << PNG_HISHIFT) + sumlo;
+}
+#endif
+mins = sum;
+}
+/* Sub filter */
+if (filter_to_do == PNG_FILTER_SUB)
+/* It's the only filter so no testing is needed */
+{
+png_bytep rp, lp, dp;
+png_size_t i;
+for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
+i++, rp++, dp++)
+{
+*dp = *rp;
+}
+for (lp = row_buf + 1; i < row_bytes;
+i++, rp++, lp++, dp++)
+{
+*dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
+}
+best_row = png_ptr->sub_row;
+}
+else if (filter_to_do & PNG_FILTER_SUB)
+{
+png_bytep rp, dp, lp;
+png_uint_32 sum = 0, lmins = mins;
+png_size_t i;
+int v;
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+/* We temporarily increase the "minimum sum" by the factor we
+* would reduce the sum of this filter, so that we can do the
+* early exit comparison without scaling the sum each time.
+*/
+if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+{
+int j;
+png_uint_32 lmhi, lmlo;
+lmlo = lmins & PNG_LOMASK;
+lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
+for (j = 0; j < num_p_filters; j++)
+{
+if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
+{
+lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+}
+}
+lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
+PNG_COST_SHIFT;
+lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
+PNG_COST_SHIFT;
+if (lmhi > PNG_HIMASK)
+lmins = PNG_MAXSUM;
+else
+lmins = (lmhi << PNG_HISHIFT) + lmlo;
+}
+#endif
+for (i = 0, rp = row_buf + 1, dp = png_ptr->sub_row + 1; i < bpp;
+i++, rp++, dp++)
+{
+v = *dp = *rp;
+sum += (v < 128) ? v : 256 - v;
+}
+for (lp = row_buf + 1; i < row_bytes;
+i++, rp++, lp++, dp++)
+{
+v = *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
+sum += (v < 128) ? v : 256 - v;
+if (sum > lmins)  /* We are already worse, don't continue. */
+break;
+}
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+{
+int j;
+png_uint_32 sumhi, sumlo;
+sumlo = sum & PNG_LOMASK;
+sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
+for (j = 0; j < num_p_filters; j++)
+{
+if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_SUB)
+{
+sumlo = (sumlo * png_ptr->inv_filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+sumhi = (sumhi * png_ptr->inv_filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+}
+}
+sumlo = (sumlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
+PNG_COST_SHIFT;
+sumhi = (sumhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_SUB]) >>
+PNG_COST_SHIFT;
+if (sumhi > PNG_HIMASK)
+sum = PNG_MAXSUM;
+else
+sum = (sumhi << PNG_HISHIFT) + sumlo;
+}
+#endif
+if (sum < mins)
+{
+mins = sum;
+best_row = png_ptr->sub_row;
+}
+}
+/* Up filter */
+if (filter_to_do == PNG_FILTER_UP)
+{
+png_bytep rp, dp, pp;
+png_size_t i;
+for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
+pp = prev_row + 1; i < row_bytes;
+i++, rp++, pp++, dp++)
+{
+*dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
+}
+best_row = png_ptr->up_row;
+}
+else if (filter_to_do & PNG_FILTER_UP)
+{
+png_bytep rp, dp, pp;
+png_uint_32 sum = 0, lmins = mins;
+png_size_t i;
+int v;
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+{
+int j;
+png_uint_32 lmhi, lmlo;
+lmlo = lmins & PNG_LOMASK;
+lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
+for (j = 0; j < num_p_filters; j++)
+{
+if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
+{
+lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+}
+}
+lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
+PNG_COST_SHIFT;
+lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_UP]) >>
+PNG_COST_SHIFT;
+if (lmhi > PNG_HIMASK)
+lmins = PNG_MAXSUM;
+else
+lmins = (lmhi << PNG_HISHIFT) + lmlo;
+}
+#endif
+for (i = 0, rp = row_buf + 1, dp = png_ptr->up_row + 1,
+pp = prev_row + 1; i < row_bytes; i++)
+{
+v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
+sum += (v < 128) ? v : 256 - v;
+if (sum > lmins)  /* We are already worse, don't continue. */
+break;
+}
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+{
+int j;
+png_uint_32 sumhi, sumlo;
+sumlo = sum & PNG_LOMASK;
+sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
+for (j = 0; j < num_p_filters; j++)
+{
+if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_UP)
+{
+sumlo = (sumlo * png_ptr->filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+sumhi = (sumhi * png_ptr->filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+}
+}
+sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
+PNG_COST_SHIFT;
+sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_UP]) >>
+PNG_COST_SHIFT;
+if (sumhi > PNG_HIMASK)
+sum = PNG_MAXSUM;
+else
+sum = (sumhi << PNG_HISHIFT) + sumlo;
+}
+#endif
+if (sum < mins)
+{
+mins = sum;
+best_row = png_ptr->up_row;
+}
+}
+/* Avg filter */
+if (filter_to_do == PNG_FILTER_AVG)
+{
+png_bytep rp, dp, pp, lp;
+png_uint_32 i;
+for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
+pp = prev_row + 1; i < bpp; i++)
+{
+*dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
+}
+for (lp = row_buf + 1; i < row_bytes; i++)
+{
+*dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
+& 0xff);
+}
+best_row = png_ptr->avg_row;
+}
+else if (filter_to_do & PNG_FILTER_AVG)
+{
+png_bytep rp, dp, pp, lp;
+png_uint_32 sum = 0, lmins = mins;
+png_size_t i;
+int v;
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+{
+int j;
+png_uint_32 lmhi, lmlo;
+lmlo = lmins & PNG_LOMASK;
+lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
+for (j = 0; j < num_p_filters; j++)
+{
+if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_AVG)
+{
+lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+}
+}
+lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
+PNG_COST_SHIFT;
+lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_AVG]) >>
+PNG_COST_SHIFT;
+if (lmhi > PNG_HIMASK)
+lmins = PNG_MAXSUM;
+else
+lmins = (lmhi << PNG_HISHIFT) + lmlo;
+}
+#endif
+for (i = 0, rp = row_buf + 1, dp = png_ptr->avg_row + 1,
+pp = prev_row + 1; i < bpp; i++)
+{
+v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
+sum += (v < 128) ? v : 256 - v;
+}
+for (lp = row_buf + 1; i < row_bytes; i++)
+{
+v = *dp++ =
+(png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2)) & 0xff);
+sum += (v < 128) ? v : 256 - v;
+if (sum > lmins)  /* We are already worse, don't continue. */
+break;
+}
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+{
+int j;
+png_uint_32 sumhi, sumlo;
+sumlo = sum & PNG_LOMASK;
+sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
+for (j = 0; j < num_p_filters; j++)
+{
+if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_NONE)
+{
+sumlo = (sumlo * png_ptr->filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+sumhi = (sumhi * png_ptr->filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+}
+}
+sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
+PNG_COST_SHIFT;
+sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_AVG]) >>
+PNG_COST_SHIFT;
+if (sumhi > PNG_HIMASK)
+sum = PNG_MAXSUM;
+else
+sum = (sumhi << PNG_HISHIFT) + sumlo;
+}
+#endif
+if (sum < mins)
+{
+mins = sum;
+best_row = png_ptr->avg_row;
+}
+}
+/* Paeth filter */
+if (filter_to_do == PNG_FILTER_PAETH)
+{
+png_bytep rp, dp, pp, cp, lp;
+png_size_t i;
+for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
+pp = prev_row + 1; i < bpp; i++)
+{
+*dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
+}
+for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
+{
+int a, b, c, pa, pb, pc, p;
+b = *pp++;
+c = *cp++;
+a = *lp++;
+p = b - c;
+pc = a - c;
+#ifdef PNG_USE_ABS
+pa = abs(p);
+pb = abs(pc);
+pc = abs(p + pc);
+#else
+pa = p < 0 ? -p : p;
+pb = pc < 0 ? -pc : pc;
+pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+#endif
+p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
+*dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
+}
+best_row = png_ptr->paeth_row;
+}
+else if (filter_to_do & PNG_FILTER_PAETH)
+{
+png_bytep rp, dp, pp, cp, lp;
+png_uint_32 sum = 0, lmins = mins;
+png_size_t i;
+int v;
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+{
+int j;
+png_uint_32 lmhi, lmlo;
+lmlo = lmins & PNG_LOMASK;
+lmhi = (lmins >> PNG_HISHIFT) & PNG_HIMASK;
+for (j = 0; j < num_p_filters; j++)
+{
+if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
+{
+lmlo = (lmlo * png_ptr->inv_filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+lmhi = (lmhi * png_ptr->inv_filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+}
+}
+lmlo = (lmlo * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
+PNG_COST_SHIFT;
+lmhi = (lmhi * png_ptr->inv_filter_costs[PNG_FILTER_VALUE_PAETH]) >>
+PNG_COST_SHIFT;
+if (lmhi > PNG_HIMASK)
+lmins = PNG_MAXSUM;
+else
+lmins = (lmhi << PNG_HISHIFT) + lmlo;
+}
+#endif
+for (i = 0, rp = row_buf + 1, dp = png_ptr->paeth_row + 1,
+pp = prev_row + 1; i < bpp; i++)
+{
+v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
+sum += (v < 128) ? v : 256 - v;
+}
+for (lp = row_buf + 1, cp = prev_row + 1; i < row_bytes; i++)
+{
+int a, b, c, pa, pb, pc, p;
+b = *pp++;
+c = *cp++;
+a = *lp++;
+#ifndef PNG_SLOW_PAETH
+p = b - c;
+pc = a - c;
+#ifdef PNG_USE_ABS
+pa = abs(p);
+pb = abs(pc);
+pc = abs(p + pc);
+#else
+pa = p < 0 ? -p : p;
+pb = pc < 0 ? -pc : pc;
+pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+#endif
+p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
+#else /* PNG_SLOW_PAETH */
+p = a + b - c;
+pa = abs(p - a);
+pb = abs(p - b);
+pc = abs(p - c);
+if (pa <= pb && pa <= pc)
+p = a;
+else if (pb <= pc)
+p = b;
+else
+p = c;
+#endif /* PNG_SLOW_PAETH */
+v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
+sum += (v < 128) ? v : 256 - v;
+if (sum > lmins)  /* We are already worse, don't continue. */
+break;
+}
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+if (png_ptr->heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
+{
+int j;
+png_uint_32 sumhi, sumlo;
+sumlo = sum & PNG_LOMASK;
+sumhi = (sum >> PNG_HISHIFT) & PNG_HIMASK;
+for (j = 0; j < num_p_filters; j++)
+{
+if (png_ptr->prev_filters[j] == PNG_FILTER_VALUE_PAETH)
+{
+sumlo = (sumlo * png_ptr->filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+sumhi = (sumhi * png_ptr->filter_weights[j]) >>
+PNG_WEIGHT_SHIFT;
+}
+}
+sumlo = (sumlo * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
+PNG_COST_SHIFT;
+sumhi = (sumhi * png_ptr->filter_costs[PNG_FILTER_VALUE_PAETH]) >>
+PNG_COST_SHIFT;
+if (sumhi > PNG_HIMASK)
+sum = PNG_MAXSUM;
+else
+sum = (sumhi << PNG_HISHIFT) + sumlo;
+}
+#endif
+if (sum < mins)
+{
+best_row = png_ptr->paeth_row;
+}
+}
+#endif /* PNG_WRITE_FILTER_SUPPORTED */
+/* Do the actual writing of the filtered row data from the chosen filter. */
+png_write_filtered_row(png_ptr, best_row, row_info->rowbytes+1);
+#ifdef PNG_WRITE_FILTER_SUPPORTED
+#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
+/* Save the type of filter we picked this time for future calculations */
+if (png_ptr->num_prev_filters > 0)
+{
+int j;
+for (j = 1; j < num_p_filters; j++)
+{
+png_ptr->prev_filters[j] = png_ptr->prev_filters[j - 1];
+}
+png_ptr->prev_filters[j] = best_row[0];
+}
+#endif
+#endif /* PNG_WRITE_FILTER_SUPPORTED */
+}
+/* Do the actual writing of a previously filtered row. */
+static void
+png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
+png_size_t full_row_length/*includes filter byte*/)
+{
+png_debug(1, "in png_write_filtered_row");
+png_debug1(2, "filter = %d", filtered_row[0]);
+png_compress_IDAT(png_ptr, filtered_row, full_row_length, Z_NO_FLUSH);
+/* Swap the current and previous rows */
+if (png_ptr->prev_row != NULL)
+{
+png_bytep tptr;
+tptr = png_ptr->prev_row;
+png_ptr->prev_row = png_ptr->row_buf;
+png_ptr->row_buf = tptr;
+}
+/* Finish row - updates counters and flushes zlib if last row */
+png_write_finish_row(png_ptr);
+#ifdef PNG_WRITE_FLUSH_SUPPORTED
+png_ptr->flush_rows++;
+if (png_ptr->flush_dist > 0 &&
+png_ptr->flush_rows >= png_ptr->flush_dist)
+{
+png_write_flush(png_ptr);
+}
+#endif
+}
+#ifdef PNG_WRITE_APNG_SUPPORTED
+void /* PRIVATE */
+png_write_reset(png_structp png_ptr)
+{
+png_ptr->row_number = 0;
+png_ptr->pass = 0;
+png_ptr->mode &= ~PNG_HAVE_IDAT;
+}
+void /* PRIVATE */
+png_write_reinit(png_structp png_ptr, png_infop info_ptr,
+png_uint_32 width, png_uint_32 height)
+{
+if (png_ptr->num_frames_written == 0 &&
+(width != png_ptr->first_frame_width ||
+height != png_ptr->first_frame_height))
+png_error(png_ptr, "width and/or height in the first frame's fcTL "
+"don't match the ones in IHDR");
+if (width > png_ptr->first_frame_width ||
+height > png_ptr->first_frame_height)
+png_error(png_ptr, "width and/or height for a frame greater than"
+"the ones in IHDR");
+png_set_IHDR(png_ptr, info_ptr, width, height,
+info_ptr->bit_depth, info_ptr->color_type,
+info_ptr->interlace_type, info_ptr->compression_type,
+info_ptr->filter_type);
+png_ptr->width = width;
+png_ptr->height = height;
+png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, width);
+png_ptr->usr_width = png_ptr->width;
+}
+#endif /* PNG_WRITE_APNG_SUPPORTED */
+#endif /* PNG_WRITE_SUPPORTED */

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media/libpng/pngwutil.c