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Add a new libjpeg API function (jpeg_skip_scanlines()) to allow for partially decoding a JPEG image.

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git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@1582 632fc199-4ca6-4c93-a231-07263d6284db
This commit is contained in:
DRC
2015-06-25 03:44:36 +00:00
parent 691cd93383
commit eb32cc1e6d
14 changed files with 588 additions and 203 deletions
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64
djpeg.c
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@@ -4,7 +4,8 @@
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1991-1997, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2010-2011, 2013-2014, D. R. Commander.
* Copyright (C) 2010-2011, 2013-2015, D. R. Commander.
* Copyright (C) 2015, Google, Inc.
* For conditions of distribution and use, see the accompanying README file.
*
* This file contains a command-line user interface for the JPEG decompressor.
@@ -88,6 +89,8 @@ 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 stripe;
JDIMENSION startY, endY;
#define INPUT_BUF_SIZE 4096
@@ -164,6 +167,7 @@ usage (void)
fprintf(stderr, " -memsrc Load input file into memory before decompressing\n");
#endif
fprintf(stderr, " -stripe Y0,Y1 Decode a horizontal stripe of the image [Y0, Y1)\n");
fprintf(stderr, " -verbose or -debug Emit debug output\n");
fprintf(stderr, " -version Print version information and exit\n");
exit(EXIT_FAILURE);
@@ -189,6 +193,7 @@ parse_switches (j_decompress_ptr cinfo, int argc, char **argv,
requested_fmt = DEFAULT_FMT; /* set default output file format */
outfilename = NULL;
memsrc = FALSE;
stripe = FALSE;
cinfo->err->trace_level = 0;
/* Scan command line options, adjust parameters */
@@ -361,7 +366,7 @@ parse_switches (j_decompress_ptr cinfo, int argc, char **argv,
/* RLE output format. */
requested_fmt = FMT_RLE;
} else if (keymatch(arg, "scale", 1)) {
} else if (keymatch(arg, "scale", 2)) {
/* Scale the output image by a fraction M/N. */
if (++argn >= argc) /* advance to next argument */
usage();
@@ -369,6 +374,13 @@ parse_switches (j_decompress_ptr cinfo, int argc, char **argv,
&cinfo->scale_num, &cinfo->scale_denom) != 2)
usage();
} else if (keymatch(arg, "stripe", 2)) {
if (++argn >= argc)
usage();
if (sscanf(argv[argn], "%d,%d", &startY, &endY) != 2 || startY > endY)
usage();
stripe = TRUE;
} else if (keymatch(arg, "targa", 1)) {
/* Targa output format. */
requested_fmt = FMT_TARGA;
@@ -634,14 +646,48 @@ main (int argc, char **argv)
/* Start decompressor */
(void) jpeg_start_decompress(&cinfo);
/* Write output file header */
(*dest_mgr->start_output) (&cinfo, dest_mgr);
/* Stripe decode */
if (stripe) {
JDIMENSION tmp;
/* Process data */
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);
/* Check for valid endY. We cannot check this value until after
* jpeg_start_decompress() is called. Note that we have already verified
* that startY <= endY.
*/
if (endY > cinfo.output_height) {
fprintf(stderr, "%s: stripe %d-%d exceeds image height %d\n", progname,
startY, endY, 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.
*/
tmp = cinfo.output_height;
cinfo.output_height = endY - startY;
(*dest_mgr->start_output) (&cinfo, dest_mgr);
cinfo.output_height = tmp;
/* Process data */
(void) 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);
}
(void) jpeg_skip_scanlines(&cinfo, cinfo.output_height - endY);
/* Normal full image decode */
} else {
/* Write output file header */
(*dest_mgr->start_output) (&cinfo, dest_mgr);
/* Process data */
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);
}
}
#ifdef PROGRESS_REPORT