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libjpeg API: Partial scanline decompression

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This, in combination with the existing jpeg_skip_scanlines() function,
provides the ability to crop the image both horizontally and vertically
while decompressing (certain restrictions apply-- see libjpeg.txt.)

This also cleans up the documentation of the line skipping feature and
removes the "strip decompression" feature from djpeg, since the new
cropping feature is a superset of it.

Refer to #34 for discussion.

Closes #34
This commit is contained in:
DRC
2016-02-19 18:32:10 -06:00
parent 5f972324ee
commit 3ab68cf563
21 changed files with 448 additions and 198 deletions
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123
djpeg.c
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@@ -5,7 +5,7 @@
* Copyright (C) 1991-1997, Thomas G. Lane.
* Modified 2013 by Guido Vollbeding.
* libjpeg-turbo Modifications:
* Copyright (C) 2010-2011, 2013-2015, D. R. Commander.
* Copyright (C) 2010-2011, 2013-2016, D. R. Commander.
* Copyright (C) 2015, Google, Inc.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
@@ -31,6 +31,7 @@
#include "cdjpeg.h" /* Common decls for cjpeg/djpeg applications */
#include "jversion.h" /* for version message */
#include "jconfigint.h"
#include "wrppm.h"
#include <ctype.h> /* to declare isprint() */
@@ -91,8 +92,9 @@ static IMAGE_FORMATS requested_fmt;
static const char *progname; /* program name for error messages */
static char *outfilename; /* for -outfile switch */
boolean memsrc; /* for -memsrc switch */
boolean strip, skip;
JDIMENSION startY, endY;
boolean skip, crop;
JDIMENSION skip_start, skip_end;
JDIMENSION crop_x, crop_y, crop_width, crop_height;
#define INPUT_BUF_SIZE 4096
@@ -169,8 +171,8 @@ usage (void)
fprintf(stderr, " -memsrc Load input file into memory before decompressing\n");
#endif
fprintf(stderr, " -skip Y0,Y1 Decode all rows except those between Y0 and Y1 (inclusive)\n");
fprintf(stderr, " -strip Y0,Y1 Decode only rows between Y0 and Y1 (inclusive)\n");
fprintf(stderr, " -skip Y0,Y1 Decompress all rows except those between Y0 and Y1 (inclusive)\n");
fprintf(stderr, " -crop WxH+X+Y Decompress only a rectangular subregion of the image\n");
fprintf(stderr, " -verbose or -debug Emit debug output\n");
fprintf(stderr, " -version Print version information and exit\n");
exit(EXIT_FAILURE);
@@ -196,8 +198,8 @@ parse_switches (j_decompress_ptr cinfo, int argc, char **argv,
requested_fmt = DEFAULT_FMT; /* set default output file format */
outfilename = NULL;
memsrc = FALSE;
strip = FALSE;
skip = FALSE;
crop = FALSE;
cinfo->err->trace_level = 0;
/* Scan command line options, adjust parameters */
@@ -378,21 +380,24 @@ parse_switches (j_decompress_ptr cinfo, int argc, char **argv,
&cinfo->scale_num, &cinfo->scale_denom) != 2)
usage();
} else if (keymatch(arg, "strip", 2)) {
if (++argn >= argc)
usage();
if (sscanf(argv[argn], "%d,%d", &startY, &endY) != 2 || startY > endY)
usage();
strip = TRUE;
} else if (keymatch(arg, "skip", 2)) {
if (++argn >= argc)
usage();
if (sscanf(argv[argn], "%d,%d", &startY, &endY) != 2 || startY > endY)
if (sscanf(argv[argn], "%u,%u", &skip_start, &skip_end) != 2 ||
skip_start > skip_end)
usage();
skip = TRUE;
} else if (keymatch(arg, "crop", 2)) {
char c;
if (++argn >= argc)
usage();
if (sscanf(argv[argn], "%u%c%u+%u+%u", &crop_width, &c, &crop_height,
&crop_x, &crop_y) != 5 ||
(c != 'X' && c != 'x') || crop_width < 1 || crop_height < 1)
usage();
crop = TRUE;
} else if (keymatch(arg, "targa", 1)) {
/* Targa output format. */
requested_fmt = FMT_TARGA;
@@ -658,54 +663,78 @@ main (int argc, char **argv)
/* Start decompressor */
(void) jpeg_start_decompress(&cinfo);
/* Strip decode */
if (strip || skip) {
/* Skip rows */
if (skip) {
JDIMENSION tmp;
/* Check for valid endY. We cannot check this value until after
/* Check for valid skip_end. We cannot check this value until after
* jpeg_start_decompress() is called. Note that we have already verified
* that startY <= endY.
* that skip_start <= skip_end.
*/
if (endY > cinfo.output_height - 1) {
fprintf(stderr, "%s: strip %d-%d exceeds image height %d\n", progname,
startY, endY, cinfo.output_height);
if (skip_end > cinfo.output_height - 1) {
fprintf(stderr, "%s: skip region exceeds image height %d\n", progname,
cinfo.output_height);
exit(EXIT_FAILURE);
}
/* Write output file header. This is a hack to ensure that the destination
* manager creates an image of the proper size for the partial decode.
* manager creates an output image of the proper size.
*/
tmp = cinfo.output_height;
cinfo.output_height = endY - startY + 1;
if (skip)
cinfo.output_height = tmp - cinfo.output_height;
cinfo.output_height -= (skip_end - skip_start + 1);
(*dest_mgr->start_output) (&cinfo, dest_mgr);
cinfo.output_height = tmp;
/* Process data */
if (skip) {
while (cinfo.output_scanline < startY) {
num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
dest_mgr->buffer_height);
(*dest_mgr->put_pixel_rows) (&cinfo, dest_mgr, num_scanlines);
}
jpeg_skip_scanlines(&cinfo, endY - startY + 1);
while (cinfo.output_scanline < cinfo.output_height) {
num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
dest_mgr->buffer_height);
(*dest_mgr->put_pixel_rows) (&cinfo, dest_mgr, num_scanlines);
}
} else {
jpeg_skip_scanlines(&cinfo, startY);
while (cinfo.output_scanline <= endY) {
num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
dest_mgr->buffer_height);
(*dest_mgr->put_pixel_rows) (&cinfo, dest_mgr, num_scanlines);
}
jpeg_skip_scanlines(&cinfo, cinfo.output_height - endY + 1);
while (cinfo.output_scanline < skip_start) {
num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
dest_mgr->buffer_height);
(*dest_mgr->put_pixel_rows) (&cinfo, dest_mgr, num_scanlines);
}
jpeg_skip_scanlines(&cinfo, skip_end - skip_start + 1);
while (cinfo.output_scanline < cinfo.output_height) {
num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
dest_mgr->buffer_height);
(*dest_mgr->put_pixel_rows) (&cinfo, dest_mgr, num_scanlines);
}
/* Normal full image decode */
/* Decompress a subregion */
} else if (crop) {
JDIMENSION tmp;
/* Check for valid crop dimensions. We cannot check these values until
* after jpeg_start_decompress() is called.
*/
if (crop_x + crop_width > cinfo.output_width ||
crop_y + crop_height > cinfo.output_height) {
fprintf(stderr, "%s: crop dimensions exceed image dimensions %d x %d\n",
progname, cinfo.output_width, cinfo.output_height);
exit(EXIT_FAILURE);
}
jpeg_crop_scanline(&cinfo, &crop_x, &crop_width);
((ppm_dest_ptr) dest_mgr)->buffer_width = cinfo.output_width *
cinfo.out_color_components *
sizeof(JSAMPLE);
/* Write output file header. This is a hack to ensure that the destination
* manager creates an output image of the proper size.
*/
tmp = cinfo.output_height;
cinfo.output_height = crop_height;
(*dest_mgr->start_output) (&cinfo, dest_mgr);
cinfo.output_height = tmp;
/* Process data */
jpeg_skip_scanlines(&cinfo, crop_y);
while (cinfo.output_scanline < crop_y + crop_height) {
num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
dest_mgr->buffer_height);
(*dest_mgr->put_pixel_rows) (&cinfo, dest_mgr, num_scanlines);
}
jpeg_skip_scanlines(&cinfo, cinfo.output_height - crop_y - crop_height);
/* Normal full-image decompress */
} else {
/* Write output file header */
(*dest_mgr->start_output) (&cinfo, dest_mgr);