The Tor Browser: media/libjpeg/jcsample.c@b8a032363ba2 (annotated)

media/libjpeg/jcsample.c@b8a032363ba2 (annotated)

media/libjpeg/jcsample.c

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /*
  * jcsample.c
  *
  * Copyright (C) 1991-1996, Thomas G. Lane.
  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains downsampling routines.
  *
  * Downsampling input data is counted in "row groups".  A row group
  * is defined to be max_v_samp_factor pixel rows of each component,
  * from which the downsampler produces v_samp_factor sample rows.
  * A single row group is processed in each call to the downsampler module.
  *
  * The downsampler is responsible for edge-expansion of its output data
  * to fill an integral number of DCT blocks horizontally.  The source buffer
  * may be modified if it is helpful for this purpose (the source buffer is
  * allocated wide enough to correspond to the desired output width).
  * The caller (the prep controller) is responsible for vertical padding.
  *
  * The downsampler may request "context rows" by setting need_context_rows
  * during startup.  In this case, the input arrays will contain at least
  * one row group's worth of pixels above and below the passed-in data;
  * the caller will create dummy rows at image top and bottom by replicating
  * the first or last real pixel row.
  *
  * An excellent reference for image resampling is
  *   Digital Image Warping, George Wolberg, 1990.
  *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
  *
  * The downsampling algorithm used here is a simple average of the source
  * pixels covered by the output pixel.  The hi-falutin sampling literature
  * refers to this as a "box filter".  In general the characteristics of a box
  * filter are not very good, but for the specific cases we normally use (1:1
  * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not
  * nearly so bad.  If you intend to use other sampling ratios, you'd be well
  * advised to improve this code.
  *
  * A simple input-smoothing capability is provided.  This is mainly intended
  * for cleaning up color-dithered GIF input files (if you find it inadequate,
  * we suggest using an external filtering program such as pnmconvol).  When
  * enabled, each input pixel P is replaced by a weighted sum of itself and its
  * eight neighbors.  P's weight is 1-8*SF and each neighbor's weight is SF,
  * where SF = (smoothing_factor / 1024).
  * Currently, smoothing is only supported for 2h2v sampling factors.
  */
 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "jpeglib.h"
 #include "jsimd.h"
 /* Pointer to routine to downsample a single component */
 typedef JMETHOD(void, downsample1_ptr,
 		(j_compress_ptr cinfo, jpeg_component_info * compptr,
 		 JSAMPARRAY input_data, JSAMPARRAY output_data));
 /* Private subobject */
 typedef struct {
   struct jpeg_downsampler pub;	/* public fields */
   /* Downsampling method pointers, one per component */
   downsample1_ptr methods[MAX_COMPONENTS];
 } my_downsampler;
 typedef my_downsampler * my_downsample_ptr;
 /*
  * Initialize for a downsampling pass.
  */
 METHODDEF(void)
 start_pass_downsample (j_compress_ptr cinfo)
 {
   /* no work for now */
 }
 /*
  * Expand a component horizontally from width input_cols to width output_cols,
  * by duplicating the rightmost samples.
  */
 LOCAL(void)
 expand_right_edge (JSAMPARRAY image_data, int num_rows,
 		   JDIMENSION input_cols, JDIMENSION output_cols)
 {
   register JSAMPROW ptr;
   register JSAMPLE pixval;
   register int count;
   int row;
   int numcols = (int) (output_cols - input_cols);
   if (numcols > 0) {
     for (row = 0; row < num_rows; row++) {
       ptr = image_data[row] + input_cols;
       pixval = ptr[-1];		/* don't need GETJSAMPLE() here */
       for (count = numcols; count > 0; count--)
 	*ptr++ = pixval;
     }
   }
 }
 /*
  * Do downsampling for a whole row group (all components).
  *
  * In this version we simply downsample each component independently.
  */
 METHODDEF(void)
 sep_downsample (j_compress_ptr cinfo,
 		JSAMPIMAGE input_buf, JDIMENSION in_row_index,
 		JSAMPIMAGE output_buf, JDIMENSION out_row_group_index)
 {
   my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample;
   int ci;
   jpeg_component_info * compptr;
   JSAMPARRAY in_ptr, out_ptr;
   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
        ci++, compptr++) {
     in_ptr = input_buf[ci] + in_row_index;
     out_ptr = output_buf[ci] + (out_row_group_index * compptr->v_samp_factor);
     (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr);
   }
 }
 /*
  * Downsample pixel values of a single component.
  * One row group is processed per call.
  * This version handles arbitrary integral sampling ratios, without smoothing.
  * Note that this version is not actually used for customary sampling ratios.
  */
 METHODDEF(void)
 int_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
 		JSAMPARRAY input_data, JSAMPARRAY output_data)
 {
   int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
   JDIMENSION outcol, outcol_h;	/* outcol_h == outcol*h_expand */
   JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
   JSAMPROW inptr, outptr;
   INT32 outvalue;
   h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
   v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
   numpix = h_expand * v_expand;
   numpix2 = numpix/2;
   /* Expand input data enough to let all the output samples be generated
    * by the standard loop.  Special-casing padded output would be more
    * efficient.
    */
   expand_right_edge(input_data, cinfo->max_v_samp_factor,
 		    cinfo->image_width, output_cols * h_expand);
   inrow = 0;
   for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
     outptr = output_data[outrow];
     for (outcol = 0, outcol_h = 0; outcol < output_cols;
 	 outcol++, outcol_h += h_expand) {
       outvalue = 0;
       for (v = 0; v < v_expand; v++) {
 	inptr = input_data[inrow+v] + outcol_h;
 	for (h = 0; h < h_expand; h++) {
 	  outvalue += (INT32) GETJSAMPLE(*inptr++);
 	}
       }
       *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix);
     }
     inrow += v_expand;
   }
 }
 /*
  * Downsample pixel values of a single component.
  * This version handles the special case of a full-size component,
  * without smoothing.
  */
 METHODDEF(void)
 fullsize_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
 		     JSAMPARRAY input_data, JSAMPARRAY output_data)
 {
   /* Copy the data */
   jcopy_sample_rows(input_data, 0, output_data, 0,
 		    cinfo->max_v_samp_factor, cinfo->image_width);
   /* Edge-expand */
   expand_right_edge(output_data, cinfo->max_v_samp_factor,
 		    cinfo->image_width, compptr->width_in_blocks * DCTSIZE);
 }
 /*
  * Downsample pixel values of a single component.
  * This version handles the common case of 2:1 horizontal and 1:1 vertical,
  * without smoothing.
  *
  * A note about the "bias" calculations: when rounding fractional values to
  * integer, we do not want to always round 0.5 up to the next integer.
  * If we did that, we'd introduce a noticeable bias towards larger values.
  * Instead, this code is arranged so that 0.5 will be rounded up or down at
  * alternate pixel locations (a simple ordered dither pattern).
  */
 METHODDEF(void)
 h2v1_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
 		 JSAMPARRAY input_data, JSAMPARRAY output_data)
 {
   int outrow;
   JDIMENSION outcol;
   JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
   register JSAMPROW inptr, outptr;
   register int bias;
   /* Expand input data enough to let all the output samples be generated
    * by the standard loop.  Special-casing padded output would be more
    * efficient.
    */
   expand_right_edge(input_data, cinfo->max_v_samp_factor,
 		    cinfo->image_width, output_cols * 2);
   for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
     outptr = output_data[outrow];
     inptr = input_data[outrow];
     bias = 0;			/* bias = 0,1,0,1,... for successive samples */
     for (outcol = 0; outcol < output_cols; outcol++) {
       *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1])
 			      + bias) >> 1);
       bias ^= 1;		/* 0=>1, 1=>0 */
       inptr += 2;
     }
   }
 }
 /*
  * Downsample pixel values of a single component.
  * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
  * without smoothing.
  */
 METHODDEF(void)
 h2v2_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
 		 JSAMPARRAY input_data, JSAMPARRAY output_data)
 {
   int inrow, outrow;
   JDIMENSION outcol;
   JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
   register JSAMPROW inptr0, inptr1, outptr;
   register int bias;
   /* Expand input data enough to let all the output samples be generated
    * by the standard loop.  Special-casing padded output would be more
    * efficient.
    */
   expand_right_edge(input_data, cinfo->max_v_samp_factor,
 		    cinfo->image_width, output_cols * 2);
   inrow = 0;
   for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
     outptr = output_data[outrow];
     inptr0 = input_data[inrow];
     inptr1 = input_data[inrow+1];
     bias = 1;			/* bias = 1,2,1,2,... for successive samples */
     for (outcol = 0; outcol < output_cols; outcol++) {
       *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
 			      GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1])
 			      + bias) >> 2);
       bias ^= 3;		/* 1=>2, 2=>1 */
       inptr0 += 2; inptr1 += 2;
     }
     inrow += 2;
   }
 }
 #ifdef INPUT_SMOOTHING_SUPPORTED
 /*
  * Downsample pixel values of a single component.
  * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
  * with smoothing.  One row of context is required.
  */
 METHODDEF(void)
 h2v2_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
 			JSAMPARRAY input_data, JSAMPARRAY output_data)
 {
   int inrow, outrow;
   JDIMENSION colctr;
   JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
   register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;
   INT32 membersum, neighsum, memberscale, neighscale;
   /* Expand input data enough to let all the output samples be generated
    * by the standard loop.  Special-casing padded output would be more
    * efficient.
    */
   expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
 		    cinfo->image_width, output_cols * 2);
   /* We don't bother to form the individual "smoothed" input pixel values;
    * we can directly compute the output which is the average of the four
    * smoothed values.  Each of the four member pixels contributes a fraction
    * (1-8*SF) to its own smoothed image and a fraction SF to each of the three
    * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final
    * output.  The four corner-adjacent neighbor pixels contribute a fraction
    * SF to just one smoothed pixel, or SF/4 to the final output; while the
    * eight edge-adjacent neighbors contribute SF to each of two smoothed
    * pixels, or SF/2 overall.  In order to use integer arithmetic, these
    * factors are scaled by 2^16 = 65536.
    * Also recall that SF = smoothing_factor / 1024.
    */
   memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */
   neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */
   inrow = 0;
   for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
     outptr = output_data[outrow];
     inptr0 = input_data[inrow];
     inptr1 = input_data[inrow+1];
     above_ptr = input_data[inrow-1];
     below_ptr = input_data[inrow+2];
     /* Special case for first column: pretend column -1 is same as column 0 */
     membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
 		GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
     neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
 	       GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
 	       GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +
 	       GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);
     neighsum += neighsum;
     neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +
 		GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);
     membersum = membersum * memberscale + neighsum * neighscale;
     *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
     inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
     for (colctr = output_cols - 2; colctr > 0; colctr--) {
       /* sum of pixels directly mapped to this output element */
       membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
 		  GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
       /* sum of edge-neighbor pixels */
       neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
 		 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
 		 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +
 		 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);
       /* The edge-neighbors count twice as much as corner-neighbors */
       neighsum += neighsum;
       /* Add in the corner-neighbors */
       neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +
 		  GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);
       /* form final output scaled up by 2^16 */
       membersum = membersum * memberscale + neighsum * neighscale;
       /* round, descale and output it */
       *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
       inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
     }
     /* Special case for last column */
     membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
 		GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
     neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
 	       GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
 	       GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +
 	       GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);
     neighsum += neighsum;
     neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +
 		GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);
     membersum = membersum * memberscale + neighsum * neighscale;
     *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
     inrow += 2;
   }
 }
 /*
  * Downsample pixel values of a single component.
  * This version handles the special case of a full-size component,
  * with smoothing.  One row of context is required.
  */
 METHODDEF(void)
 fullsize_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info *compptr,
 			    JSAMPARRAY input_data, JSAMPARRAY output_data)
 {
   int outrow;
   JDIMENSION colctr;
   JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
   register JSAMPROW inptr, above_ptr, below_ptr, outptr;
   INT32 membersum, neighsum, memberscale, neighscale;
   int colsum, lastcolsum, nextcolsum;
   /* Expand input data enough to let all the output samples be generated
    * by the standard loop.  Special-casing padded output would be more
    * efficient.
    */
   expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
 		    cinfo->image_width, output_cols);
   /* Each of the eight neighbor pixels contributes a fraction SF to the
    * smoothed pixel, while the main pixel contributes (1-8*SF).  In order
    * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
    * Also recall that SF = smoothing_factor / 1024.
    */
   memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */
   neighscale = cinfo->smoothing_factor * 64; /* scaled SF */
   for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
     outptr = output_data[outrow];
     inptr = input_data[outrow];
     above_ptr = input_data[outrow-1];
     below_ptr = input_data[outrow+1];
     /* Special case for first column */
     colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +
 	     GETJSAMPLE(*inptr);
     membersum = GETJSAMPLE(*inptr++);
     nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
 		 GETJSAMPLE(*inptr);
     neighsum = colsum + (colsum - membersum) + nextcolsum;
     membersum = membersum * memberscale + neighsum * neighscale;
     *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
     lastcolsum = colsum; colsum = nextcolsum;
     for (colctr = output_cols - 2; colctr > 0; colctr--) {
       membersum = GETJSAMPLE(*inptr++);
       above_ptr++; below_ptr++;
       nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
 		   GETJSAMPLE(*inptr);
       neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
       membersum = membersum * memberscale + neighsum * neighscale;
       *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
       lastcolsum = colsum; colsum = nextcolsum;
     }
     /* Special case for last column */
     membersum = GETJSAMPLE(*inptr);
     neighsum = lastcolsum + (colsum - membersum) + colsum;
     membersum = membersum * memberscale + neighsum * neighscale;
     *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
   }
 }
 #endif /* INPUT_SMOOTHING_SUPPORTED */
 /*
  * Module initialization routine for downsampling.
  * Note that we must select a routine for each component.
  */
 GLOBAL(void)
 jinit_downsampler (j_compress_ptr cinfo)
 {
   my_downsample_ptr downsample;
   int ci;
   jpeg_component_info * compptr;
   boolean smoothok = TRUE;
   downsample = (my_downsample_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				SIZEOF(my_downsampler));
   cinfo->downsample = (struct jpeg_downsampler *) downsample;
   downsample->pub.start_pass = start_pass_downsample;
   downsample->pub.downsample = sep_downsample;
   downsample->pub.need_context_rows = FALSE;
   if (cinfo->CCIR601_sampling)
     ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
   /* Verify we can handle the sampling factors, and set up method pointers */
   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
        ci++, compptr++) {
     if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
 	compptr->v_samp_factor == cinfo->max_v_samp_factor) {
 #ifdef INPUT_SMOOTHING_SUPPORTED
       if (cinfo->smoothing_factor) {
 	downsample->methods[ci] = fullsize_smooth_downsample;
 	downsample->pub.need_context_rows = TRUE;
       } else
 #endif
 	downsample->methods[ci] = fullsize_downsample;
     } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
 	       compptr->v_samp_factor == cinfo->max_v_samp_factor) {
       smoothok = FALSE;
       if (jsimd_can_h2v1_downsample())
         downsample->methods[ci] = jsimd_h2v1_downsample;
       else
         downsample->methods[ci] = h2v1_downsample;
     } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
 	       compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) {
 #ifdef INPUT_SMOOTHING_SUPPORTED
       if (cinfo->smoothing_factor) {
 	downsample->methods[ci] = h2v2_smooth_downsample;
 	downsample->pub.need_context_rows = TRUE;
       } else
 #endif
 	if (jsimd_can_h2v2_downsample())
 	  downsample->methods[ci] = jsimd_h2v2_downsample;
 	else
 	  downsample->methods[ci] = h2v2_downsample;
     } else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
 	       (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) {
       smoothok = FALSE;
       downsample->methods[ci] = int_downsample;
     } else
       ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
   }
 #ifdef INPUT_SMOOTHING_SUPPORTED
   if (cinfo->smoothing_factor && !smoothok)
     TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL);
 #endif
 }

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media/libjpeg/jcsample.c@b8a032363ba2 (annotated)

media/libjpeg/jcsample.c