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51f94caba11df1b592f7477cb62768d7f6e20eda
mozjpeg/jcsample.c
DRC 19c791cdac Improve code formatting consistency 
With rare exceptions ...
- Always separate line continuation characters by one space from
  preceding code.
- Always use two-space indentation.  Never use tabs.
- Always use K&R-style conditional blocks.
- Always surround operators with spaces, except in raw assembly code.
- Always put a space after, but not before, a comma.
- Never put a space between type casts and variables/function calls.
- Never put a space between the function name and the argument list in
  function declarations and prototypes.
- Always surround braces ('{' and '}') with spaces.
- Always surround statements (if, for, else, catch, while, do, switch)
  with spaces.
- Always attach pointer symbols ('*' and '**') to the variable or
  function name.
- Always precede pointer symbols ('*' and '**') by a space in type
  casts.
- Use the MIN() macro from jpegint.h within the libjpeg and TurboJPEG
  API libraries (using min() from tjutil.h is still necessary for
  TJBench.)
- Where it makes sense (particularly in the TurboJPEG code), put a blank
  line after variable declaration blocks.
- Always separate statements in one-liners by two spaces.

The purpose of this was to ease maintenance on my part and also to make
it easier for contributors to figure out how to format patch
submissions.  This was admittedly confusing (even to me sometimes) when
we had 3 or 4 different style conventions in the same source tree.  The
new convention is more consistent with the formatting of other OSS code
bases.

This commit corrects deviations from the chosen formatting style in the
libjpeg API code and reformats the TurboJPEG API code such that it
conforms to the same standard.

NOTES:
- Although it is no longer necessary for the function name in function
  declarations to begin in Column 1 (this was historically necessary
  because of the ansi2knr utility, which allowed libjpeg to be built
  with non-ANSI compilers), we retain that formatting for the libjpeg
  code because it improves readability when using libjpeg's function
  attribute macros (GLOBAL(), etc.)
- This reformatting project was accomplished with the help of AStyle and
  Uncrustify, although neither was completely up to the task, and thus
  a great deal of manual tweaking was required.  Note to developers of
  code formatting utilities:  the libjpeg-turbo code base is an
  excellent test bed, because AFAICT, it breaks every single one of the
  utilities that are currently available.
- The legacy (MMX, SSE, 3DNow!) assembly code for i386 has been
  formatted to match the SSE2 code (refer to
  ff5685d5344273df321eb63a005eaae19d2496e3.)  I hadn't intended to
  bother with this, but the Loongson MMI implementation demonstrated
  that there is still academic value to the MMX implementation, as an
  algorithmic model for other 64-bit vector implementations.  Thus, it
  is desirable to improve its readability in the same manner as that of
  the SSE2 implementation.
2018-03-16 02:14:34 -05:00

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/*
* jcsample.c
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1991-1996, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
* Copyright (C) 2014, MIPS Technologies, Inc., California.
* Copyright (C) 2015, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* 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 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;
JLONG 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 += (JLONG)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;
JLONG 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;
JLONG 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) {
#if defined(__mips__)
if (jsimd_can_h2v2_smooth_downsample())
downsample->methods[ci] = jsimd_h2v2_smooth_downsample;
else
#endif
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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