michael@0: /*
michael@0:  *  Copyright 2012 The LibYuv Project Authors. All rights reserved.
michael@0:  *
michael@0:  *  Use of this source code is governed by a BSD-style license
michael@0:  *  that can be found in the LICENSE file in the root of the source
michael@0:  *  tree. An additional intellectual property rights grant can be found
michael@0:  *  in the file PATENTS. All contributing project authors may
michael@0:  *  be found in the AUTHORS file in the root of the source tree.
michael@0:  */
michael@0: 
michael@0: #include "libyuv/mjpeg_decoder.h"
michael@0: 
michael@0: #ifdef HAVE_JPEG
michael@0: #include <assert.h>
michael@0: 
michael@0: #if !defined(__pnacl__) && !defined(__CLR_VER) && !defined(COVERAGE_ENABLED) &&\
michael@0:     !defined(TARGET_IPHONE_SIMULATOR)
michael@0: // Must be included before jpeglib.
michael@0: #include <setjmp.h>
michael@0: #define HAVE_SETJMP
michael@0: #endif
michael@0: struct FILE;  // For jpeglib.h.
michael@0: 
michael@0: // C++ build requires extern C for jpeg internals.
michael@0: #ifdef __cplusplus
michael@0: extern "C" {
michael@0: #endif
michael@0: 
michael@0: #include <jpeglib.h>
michael@0: 
michael@0: #ifdef __cplusplus
michael@0: }  // extern "C"
michael@0: #endif
michael@0: 
michael@0: #include "libyuv/planar_functions.h"  // For CopyPlane().
michael@0: 
michael@0: namespace libyuv {
michael@0: 
michael@0: #ifdef HAVE_SETJMP
michael@0: struct SetJmpErrorMgr {
michael@0:   jpeg_error_mgr base;  // Must be at the top
michael@0:   jmp_buf setjmp_buffer;
michael@0: };
michael@0: #endif
michael@0: 
michael@0: const int MJpegDecoder::kColorSpaceUnknown = JCS_UNKNOWN;
michael@0: const int MJpegDecoder::kColorSpaceGrayscale = JCS_GRAYSCALE;
michael@0: const int MJpegDecoder::kColorSpaceRgb = JCS_RGB;
michael@0: const int MJpegDecoder::kColorSpaceYCbCr = JCS_YCbCr;
michael@0: const int MJpegDecoder::kColorSpaceCMYK = JCS_CMYK;
michael@0: const int MJpegDecoder::kColorSpaceYCCK = JCS_YCCK;
michael@0: 
michael@0: MJpegDecoder::MJpegDecoder()
michael@0:     : has_scanline_padding_(LIBYUV_FALSE),
michael@0:       num_outbufs_(0),
michael@0:       scanlines_(NULL),
michael@0:       scanlines_sizes_(NULL),
michael@0:       databuf_(NULL),
michael@0:       databuf_strides_(NULL) {
michael@0:   decompress_struct_ = new jpeg_decompress_struct;
michael@0:   source_mgr_ = new jpeg_source_mgr;
michael@0: #ifdef HAVE_SETJMP
michael@0:   error_mgr_ = new SetJmpErrorMgr;
michael@0:   decompress_struct_->err = jpeg_std_error(&error_mgr_->base);
michael@0:   // Override standard exit()-based error handler.
michael@0:   error_mgr_->base.error_exit = &ErrorHandler;
michael@0: #endif
michael@0:   decompress_struct_->client_data = NULL;
michael@0:   source_mgr_->init_source = &init_source;
michael@0:   source_mgr_->fill_input_buffer = &fill_input_buffer;
michael@0:   source_mgr_->skip_input_data = &skip_input_data;
michael@0:   source_mgr_->resync_to_restart = &jpeg_resync_to_restart;
michael@0:   source_mgr_->term_source = &term_source;
michael@0:   jpeg_create_decompress(decompress_struct_);
michael@0:   decompress_struct_->src = source_mgr_;
michael@0:   buf_vec_.buffers = &buf_;
michael@0:   buf_vec_.len = 1;
michael@0: }
michael@0: 
michael@0: MJpegDecoder::~MJpegDecoder() {
michael@0:   jpeg_destroy_decompress(decompress_struct_);
michael@0:   delete decompress_struct_;
michael@0:   delete source_mgr_;
michael@0: #ifdef HAVE_SETJMP
michael@0:   delete error_mgr_;
michael@0: #endif
michael@0:   DestroyOutputBuffers();
michael@0: }
michael@0: 
michael@0: LIBYUV_BOOL MJpegDecoder::LoadFrame(const uint8* src, size_t src_len) {
michael@0:   if (!ValidateJpeg(src, src_len)) {
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0: 
michael@0:   buf_.data = src;
michael@0:   buf_.len = (int)(src_len);
michael@0:   buf_vec_.pos = 0;
michael@0:   decompress_struct_->client_data = &buf_vec_;
michael@0: #ifdef HAVE_SETJMP
michael@0:   if (setjmp(error_mgr_->setjmp_buffer)) {
michael@0:     // We called jpeg_read_header, it experienced an error, and we called
michael@0:     // longjmp() and rewound the stack to here. Return error.
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0: #endif
michael@0:   if (jpeg_read_header(decompress_struct_, TRUE) != JPEG_HEADER_OK) {
michael@0:     // ERROR: Bad MJPEG header
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0:   AllocOutputBuffers(GetNumComponents());
michael@0:   for (int i = 0; i < num_outbufs_; ++i) {
michael@0:     int scanlines_size = GetComponentScanlinesPerImcuRow(i);
michael@0:     if (scanlines_sizes_[i] != scanlines_size) {
michael@0:       if (scanlines_[i]) {
michael@0:         delete scanlines_[i];
michael@0:       }
michael@0:       scanlines_[i] = new uint8* [scanlines_size];
michael@0:       scanlines_sizes_[i] = scanlines_size;
michael@0:     }
michael@0: 
michael@0:     // We allocate padding for the final scanline to pad it up to DCTSIZE bytes
michael@0:     // to avoid memory errors, since jpeglib only reads full MCUs blocks. For
michael@0:     // the preceding scanlines, the padding is not needed/wanted because the
michael@0:     // following addresses will already be valid (they are the initial bytes of
michael@0:     // the next scanline) and will be overwritten when jpeglib writes out that
michael@0:     // next scanline.
michael@0:     int databuf_stride = GetComponentStride(i);
michael@0:     int databuf_size = scanlines_size * databuf_stride;
michael@0:     if (databuf_strides_[i] != databuf_stride) {
michael@0:       if (databuf_[i]) {
michael@0:         delete databuf_[i];
michael@0:       }
michael@0:       databuf_[i] = new uint8[databuf_size];
michael@0:       databuf_strides_[i] = databuf_stride;
michael@0:     }
michael@0: 
michael@0:     if (GetComponentStride(i) != GetComponentWidth(i)) {
michael@0:       has_scanline_padding_ = LIBYUV_TRUE;
michael@0:     }
michael@0:   }
michael@0:   return LIBYUV_TRUE;
michael@0: }
michael@0: 
michael@0: static int DivideAndRoundUp(int numerator, int denominator) {
michael@0:   return (numerator + denominator - 1) / denominator;
michael@0: }
michael@0: 
michael@0: static int DivideAndRoundDown(int numerator, int denominator) {
michael@0:   return numerator / denominator;
michael@0: }
michael@0: 
michael@0: // Returns width of the last loaded frame.
michael@0: int MJpegDecoder::GetWidth() {
michael@0:   return decompress_struct_->image_width;
michael@0: }
michael@0: 
michael@0: // Returns height of the last loaded frame.
michael@0: int MJpegDecoder::GetHeight() {
michael@0:   return decompress_struct_->image_height;
michael@0: }
michael@0: 
michael@0: // Returns format of the last loaded frame. The return value is one of the
michael@0: // kColorSpace* constants.
michael@0: int MJpegDecoder::GetColorSpace() {
michael@0:   return decompress_struct_->jpeg_color_space;
michael@0: }
michael@0: 
michael@0: // Number of color components in the color space.
michael@0: int MJpegDecoder::GetNumComponents() {
michael@0:   return decompress_struct_->num_components;
michael@0: }
michael@0: 
michael@0: // Sample factors of the n-th component.
michael@0: int MJpegDecoder::GetHorizSampFactor(int component) {
michael@0:   return decompress_struct_->comp_info[component].h_samp_factor;
michael@0: }
michael@0: 
michael@0: int MJpegDecoder::GetVertSampFactor(int component) {
michael@0:   return decompress_struct_->comp_info[component].v_samp_factor;
michael@0: }
michael@0: 
michael@0: int MJpegDecoder::GetHorizSubSampFactor(int component) {
michael@0:   return decompress_struct_->max_h_samp_factor /
michael@0:       GetHorizSampFactor(component);
michael@0: }
michael@0: 
michael@0: int MJpegDecoder::GetVertSubSampFactor(int component) {
michael@0:   return decompress_struct_->max_v_samp_factor /
michael@0:       GetVertSampFactor(component);
michael@0: }
michael@0: 
michael@0: int MJpegDecoder::GetImageScanlinesPerImcuRow() {
michael@0:   return decompress_struct_->max_v_samp_factor * DCTSIZE;
michael@0: }
michael@0: 
michael@0: int MJpegDecoder::GetComponentScanlinesPerImcuRow(int component) {
michael@0:   int vs = GetVertSubSampFactor(component);
michael@0:   return DivideAndRoundUp(GetImageScanlinesPerImcuRow(), vs);
michael@0: }
michael@0: 
michael@0: int MJpegDecoder::GetComponentWidth(int component) {
michael@0:   int hs = GetHorizSubSampFactor(component);
michael@0:   return DivideAndRoundUp(GetWidth(), hs);
michael@0: }
michael@0: 
michael@0: int MJpegDecoder::GetComponentHeight(int component) {
michael@0:   int vs = GetVertSubSampFactor(component);
michael@0:   return DivideAndRoundUp(GetHeight(), vs);
michael@0: }
michael@0: 
michael@0: // Get width in bytes padded out to a multiple of DCTSIZE
michael@0: int MJpegDecoder::GetComponentStride(int component) {
michael@0:   return (GetComponentWidth(component) + DCTSIZE - 1) & ~(DCTSIZE - 1);
michael@0: }
michael@0: 
michael@0: int MJpegDecoder::GetComponentSize(int component) {
michael@0:   return GetComponentWidth(component) * GetComponentHeight(component);
michael@0: }
michael@0: 
michael@0: LIBYUV_BOOL MJpegDecoder::UnloadFrame() {
michael@0: #ifdef HAVE_SETJMP
michael@0:   if (setjmp(error_mgr_->setjmp_buffer)) {
michael@0:     // We called jpeg_abort_decompress, it experienced an error, and we called
michael@0:     // longjmp() and rewound the stack to here. Return error.
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0: #endif
michael@0:   jpeg_abort_decompress(decompress_struct_);
michael@0:   return LIBYUV_TRUE;
michael@0: }
michael@0: 
michael@0: // TODO(fbarchard): Allow rectangle to be specified: x, y, width, height.
michael@0: LIBYUV_BOOL MJpegDecoder::DecodeToBuffers(
michael@0:     uint8** planes, int dst_width, int dst_height) {
michael@0:   if (dst_width != GetWidth() ||
michael@0:       dst_height > GetHeight()) {
michael@0:     // ERROR: Bad dimensions
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0: #ifdef HAVE_SETJMP
michael@0:   if (setjmp(error_mgr_->setjmp_buffer)) {
michael@0:     // We called into jpeglib, it experienced an error sometime during this
michael@0:     // function call, and we called longjmp() and rewound the stack to here.
michael@0:     // Return error.
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0: #endif
michael@0:   if (!StartDecode()) {
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0:   SetScanlinePointers(databuf_);
michael@0:   int lines_left = dst_height;
michael@0:   // Compute amount of lines to skip to implement vertical crop.
michael@0:   // TODO(fbarchard): Ensure skip is a multiple of maximum component
michael@0:   // subsample. ie 2
michael@0:   int skip = (GetHeight() - dst_height) / 2;
michael@0:   if (skip > 0) {
michael@0:     // There is no API to skip lines in the output data, so we read them
michael@0:     // into the temp buffer.
michael@0:     while (skip >= GetImageScanlinesPerImcuRow()) {
michael@0:       if (!DecodeImcuRow()) {
michael@0:         FinishDecode();
michael@0:         return LIBYUV_FALSE;
michael@0:       }
michael@0:       skip -= GetImageScanlinesPerImcuRow();
michael@0:     }
michael@0:     if (skip > 0) {
michael@0:       // Have a partial iMCU row left over to skip. Must read it and then
michael@0:       // copy the parts we want into the destination.
michael@0:       if (!DecodeImcuRow()) {
michael@0:         FinishDecode();
michael@0:         return LIBYUV_FALSE;
michael@0:       }
michael@0:       for (int i = 0; i < num_outbufs_; ++i) {
michael@0:         // TODO(fbarchard): Compute skip to avoid this
michael@0:         assert(skip % GetVertSubSampFactor(i) == 0);
michael@0:         int rows_to_skip =
michael@0:             DivideAndRoundDown(skip, GetVertSubSampFactor(i));
michael@0:         int scanlines_to_copy = GetComponentScanlinesPerImcuRow(i) -
michael@0:                                 rows_to_skip;
michael@0:         int data_to_skip = rows_to_skip * GetComponentStride(i);
michael@0:         CopyPlane(databuf_[i] + data_to_skip, GetComponentStride(i),
michael@0:                   planes[i], GetComponentWidth(i),
michael@0:                   GetComponentWidth(i), scanlines_to_copy);
michael@0:         planes[i] += scanlines_to_copy * GetComponentWidth(i);
michael@0:       }
michael@0:       lines_left -= (GetImageScanlinesPerImcuRow() - skip);
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   // Read full MCUs but cropped horizontally
michael@0:   for (; lines_left > GetImageScanlinesPerImcuRow();
michael@0:          lines_left -= GetImageScanlinesPerImcuRow()) {
michael@0:     if (!DecodeImcuRow()) {
michael@0:       FinishDecode();
michael@0:       return LIBYUV_FALSE;
michael@0:     }
michael@0:     for (int i = 0; i < num_outbufs_; ++i) {
michael@0:       int scanlines_to_copy = GetComponentScanlinesPerImcuRow(i);
michael@0:       CopyPlane(databuf_[i], GetComponentStride(i),
michael@0:                 planes[i], GetComponentWidth(i),
michael@0:                 GetComponentWidth(i), scanlines_to_copy);
michael@0:       planes[i] += scanlines_to_copy * GetComponentWidth(i);
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   if (lines_left > 0) {
michael@0:     // Have a partial iMCU row left over to decode.
michael@0:     if (!DecodeImcuRow()) {
michael@0:       FinishDecode();
michael@0:       return LIBYUV_FALSE;
michael@0:     }
michael@0:     for (int i = 0; i < num_outbufs_; ++i) {
michael@0:       int scanlines_to_copy =
michael@0:           DivideAndRoundUp(lines_left, GetVertSubSampFactor(i));
michael@0:       CopyPlane(databuf_[i], GetComponentStride(i),
michael@0:                 planes[i], GetComponentWidth(i),
michael@0:                 GetComponentWidth(i), scanlines_to_copy);
michael@0:       planes[i] += scanlines_to_copy * GetComponentWidth(i);
michael@0:     }
michael@0:   }
michael@0:   return FinishDecode();
michael@0: }
michael@0: 
michael@0: LIBYUV_BOOL MJpegDecoder::DecodeToCallback(CallbackFunction fn, void* opaque,
michael@0:     int dst_width, int dst_height) {
michael@0:   if (dst_width != GetWidth() ||
michael@0:       dst_height > GetHeight()) {
michael@0:     // ERROR: Bad dimensions
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0: #ifdef HAVE_SETJMP
michael@0:   if (setjmp(error_mgr_->setjmp_buffer)) {
michael@0:     // We called into jpeglib, it experienced an error sometime during this
michael@0:     // function call, and we called longjmp() and rewound the stack to here.
michael@0:     // Return error.
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0: #endif
michael@0:   if (!StartDecode()) {
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0:   SetScanlinePointers(databuf_);
michael@0:   int lines_left = dst_height;
michael@0:   // TODO(fbarchard): Compute amount of lines to skip to implement vertical crop
michael@0:   int skip = (GetHeight() - dst_height) / 2;
michael@0:   if (skip > 0) {
michael@0:     while (skip >= GetImageScanlinesPerImcuRow()) {
michael@0:       if (!DecodeImcuRow()) {
michael@0:         FinishDecode();
michael@0:         return LIBYUV_FALSE;
michael@0:       }
michael@0:       skip -= GetImageScanlinesPerImcuRow();
michael@0:     }
michael@0:     if (skip > 0) {
michael@0:       // Have a partial iMCU row left over to skip.
michael@0:       if (!DecodeImcuRow()) {
michael@0:         FinishDecode();
michael@0:         return LIBYUV_FALSE;
michael@0:       }
michael@0:       for (int i = 0; i < num_outbufs_; ++i) {
michael@0:         // TODO(fbarchard): Compute skip to avoid this
michael@0:         assert(skip % GetVertSubSampFactor(i) == 0);
michael@0:         int rows_to_skip = DivideAndRoundDown(skip, GetVertSubSampFactor(i));
michael@0:         int data_to_skip = rows_to_skip * GetComponentStride(i);
michael@0:         // Change our own data buffer pointers so we can pass them to the
michael@0:         // callback.
michael@0:         databuf_[i] += data_to_skip;
michael@0:       }
michael@0:       int scanlines_to_copy = GetImageScanlinesPerImcuRow() - skip;
michael@0:       (*fn)(opaque, databuf_, databuf_strides_, scanlines_to_copy);
michael@0:       // Now change them back.
michael@0:       for (int i = 0; i < num_outbufs_; ++i) {
michael@0:         int rows_to_skip = DivideAndRoundDown(skip, GetVertSubSampFactor(i));
michael@0:         int data_to_skip = rows_to_skip * GetComponentStride(i);
michael@0:         databuf_[i] -= data_to_skip;
michael@0:       }
michael@0:       lines_left -= scanlines_to_copy;
michael@0:     }
michael@0:   }
michael@0:   // Read full MCUs until we get to the crop point.
michael@0:   for (; lines_left >= GetImageScanlinesPerImcuRow();
michael@0:          lines_left -= GetImageScanlinesPerImcuRow()) {
michael@0:     if (!DecodeImcuRow()) {
michael@0:       FinishDecode();
michael@0:       return LIBYUV_FALSE;
michael@0:     }
michael@0:     (*fn)(opaque, databuf_, databuf_strides_, GetImageScanlinesPerImcuRow());
michael@0:   }
michael@0:   if (lines_left > 0) {
michael@0:     // Have a partial iMCU row left over to decode.
michael@0:     if (!DecodeImcuRow()) {
michael@0:       FinishDecode();
michael@0:       return LIBYUV_FALSE;
michael@0:     }
michael@0:     (*fn)(opaque, databuf_, databuf_strides_, lines_left);
michael@0:   }
michael@0:   return FinishDecode();
michael@0: }
michael@0: 
michael@0: void MJpegDecoder::init_source(j_decompress_ptr cinfo) {
michael@0:   fill_input_buffer(cinfo);
michael@0: }
michael@0: 
michael@0: boolean MJpegDecoder::fill_input_buffer(j_decompress_ptr cinfo) {
michael@0:   BufferVector* buf_vec = (BufferVector*)(cinfo->client_data);
michael@0:   if (buf_vec->pos >= buf_vec->len) {
michael@0:     assert(0 && "No more data");
michael@0:     // ERROR: No more data
michael@0:     return FALSE;
michael@0:   }
michael@0:   cinfo->src->next_input_byte = buf_vec->buffers[buf_vec->pos].data;
michael@0:   cinfo->src->bytes_in_buffer = buf_vec->buffers[buf_vec->pos].len;
michael@0:   ++buf_vec->pos;
michael@0:   return TRUE;
michael@0: }
michael@0: 
michael@0: void MJpegDecoder::skip_input_data(j_decompress_ptr cinfo,
michael@0:                                    long num_bytes) {  // NOLINT
michael@0:   cinfo->src->next_input_byte += num_bytes;
michael@0: }
michael@0: 
michael@0: void MJpegDecoder::term_source(j_decompress_ptr cinfo) {
michael@0:   // Nothing to do.
michael@0: }
michael@0: 
michael@0: #ifdef HAVE_SETJMP
michael@0: void MJpegDecoder::ErrorHandler(j_common_ptr cinfo) {
michael@0:   // This is called when a jpeglib command experiences an error. Unfortunately
michael@0:   // jpeglib's error handling model is not very flexible, because it expects the
michael@0:   // error handler to not return--i.e., it wants the program to terminate. To
michael@0:   // recover from errors we use setjmp() as shown in their example. setjmp() is
michael@0:   // C's implementation for the "call with current continuation" functionality
michael@0:   // seen in some functional programming languages.
michael@0:   // A formatted message can be output, but is unsafe for release.
michael@0: #ifdef DEBUG
michael@0:   char buf[JMSG_LENGTH_MAX];
michael@0:   (*cinfo->err->format_message)(cinfo, buf);
michael@0:   // ERROR: Error in jpeglib: buf
michael@0: #endif
michael@0: 
michael@0:   SetJmpErrorMgr* mgr = (SetJmpErrorMgr*)(cinfo->err);
michael@0:   // This rewinds the call stack to the point of the corresponding setjmp()
michael@0:   // and causes it to return (for a second time) with value 1.
michael@0:   longjmp(mgr->setjmp_buffer, 1);
michael@0: }
michael@0: #endif
michael@0: 
michael@0: void MJpegDecoder::AllocOutputBuffers(int num_outbufs) {
michael@0:   if (num_outbufs != num_outbufs_) {
michael@0:     // We could perhaps optimize this case to resize the output buffers without
michael@0:     // necessarily having to delete and recreate each one, but it's not worth
michael@0:     // it.
michael@0:     DestroyOutputBuffers();
michael@0: 
michael@0:     scanlines_ = new uint8** [num_outbufs];
michael@0:     scanlines_sizes_ = new int[num_outbufs];
michael@0:     databuf_ = new uint8* [num_outbufs];
michael@0:     databuf_strides_ = new int[num_outbufs];
michael@0: 
michael@0:     for (int i = 0; i < num_outbufs; ++i) {
michael@0:       scanlines_[i] = NULL;
michael@0:       scanlines_sizes_[i] = 0;
michael@0:       databuf_[i] = NULL;
michael@0:       databuf_strides_[i] = 0;
michael@0:     }
michael@0: 
michael@0:     num_outbufs_ = num_outbufs;
michael@0:   }
michael@0: }
michael@0: 
michael@0: void MJpegDecoder::DestroyOutputBuffers() {
michael@0:   for (int i = 0; i < num_outbufs_; ++i) {
michael@0:     delete [] scanlines_[i];
michael@0:     delete [] databuf_[i];
michael@0:   }
michael@0:   delete [] scanlines_;
michael@0:   delete [] databuf_;
michael@0:   delete [] scanlines_sizes_;
michael@0:   delete [] databuf_strides_;
michael@0:   scanlines_ = NULL;
michael@0:   databuf_ = NULL;
michael@0:   scanlines_sizes_ = NULL;
michael@0:   databuf_strides_ = NULL;
michael@0:   num_outbufs_ = 0;
michael@0: }
michael@0: 
michael@0: // JDCT_IFAST and do_block_smoothing improve performance substantially.
michael@0: LIBYUV_BOOL MJpegDecoder::StartDecode() {
michael@0:   decompress_struct_->raw_data_out = TRUE;
michael@0:   decompress_struct_->dct_method = JDCT_IFAST;  // JDCT_ISLOW is default
michael@0:   decompress_struct_->dither_mode = JDITHER_NONE;
michael@0:   // Not applicable to 'raw':
michael@0:   decompress_struct_->do_fancy_upsampling = LIBYUV_FALSE;
michael@0:   // Only for buffered mode:
michael@0:   decompress_struct_->enable_2pass_quant = LIBYUV_FALSE;
michael@0:   // Blocky but fast:
michael@0:   decompress_struct_->do_block_smoothing = LIBYUV_FALSE;
michael@0: 
michael@0:   if (!jpeg_start_decompress(decompress_struct_)) {
michael@0:     // ERROR: Couldn't start JPEG decompressor";
michael@0:     return LIBYUV_FALSE;
michael@0:   }
michael@0:   return LIBYUV_TRUE;
michael@0: }
michael@0: 
michael@0: LIBYUV_BOOL MJpegDecoder::FinishDecode() {
michael@0:   // jpeglib considers it an error if we finish without decoding the whole
michael@0:   // image, so we call "abort" rather than "finish".
michael@0:   jpeg_abort_decompress(decompress_struct_);
michael@0:   return LIBYUV_TRUE;
michael@0: }
michael@0: 
michael@0: void MJpegDecoder::SetScanlinePointers(uint8** data) {
michael@0:   for (int i = 0; i < num_outbufs_; ++i) {
michael@0:     uint8* data_i = data[i];
michael@0:     for (int j = 0; j < scanlines_sizes_[i]; ++j) {
michael@0:       scanlines_[i][j] = data_i;
michael@0:       data_i += GetComponentStride(i);
michael@0:     }
michael@0:   }
michael@0: }
michael@0: 
michael@0: inline LIBYUV_BOOL MJpegDecoder::DecodeImcuRow() {
michael@0:   return (unsigned int)(GetImageScanlinesPerImcuRow()) ==
michael@0:       jpeg_read_raw_data(decompress_struct_,
michael@0:                          scanlines_,
michael@0:                          GetImageScanlinesPerImcuRow());
michael@0: }
michael@0: 
michael@0: // The helper function which recognizes the jpeg sub-sampling type.
michael@0: JpegSubsamplingType MJpegDecoder::JpegSubsamplingTypeHelper(
michael@0:     int* subsample_x, int* subsample_y, int number_of_components) {
michael@0:   if (number_of_components == 3) {  // Color images.
michael@0:     if (subsample_x[0] == 1 && subsample_y[0] == 1 &&
michael@0:         subsample_x[1] == 2 && subsample_y[1] == 2 &&
michael@0:         subsample_x[2] == 2 && subsample_y[2] == 2) {
michael@0:       return kJpegYuv420;
michael@0:     } else if (subsample_x[0] == 1 && subsample_y[0] == 1 &&
michael@0:         subsample_x[1] == 2 && subsample_y[1] == 1 &&
michael@0:         subsample_x[2] == 2 && subsample_y[2] == 1) {
michael@0:       return kJpegYuv422;
michael@0:     } else if (subsample_x[0] == 1 && subsample_y[0] == 1 &&
michael@0:         subsample_x[1] == 1 && subsample_y[1] == 1 &&
michael@0:         subsample_x[2] == 1 && subsample_y[2] == 1) {
michael@0:       return kJpegYuv444;
michael@0:     }
michael@0:   } else if (number_of_components == 1) {  // Grey-scale images.
michael@0:     if (subsample_x[0] == 1 && subsample_y[0] == 1) {
michael@0:       return kJpegYuv400;
michael@0:     }
michael@0:   }
michael@0:   return kJpegUnknown;
michael@0: }
michael@0: 
michael@0: }  // namespace libyuv
michael@0: #endif  // HAVE_JPEG
michael@0: