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"test-png" tool to find PNGs that cause warnings

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New tool, "test-png", which exercises libpng library on
a set of PNG image files, allowing us to find those which
cause Tux Paint (via SDL_image, in turn via libpng) to
report back warnings to STDERR.

h/t Tim Dickson, per https://sourceforge.net/p/tuxpaint/bugs/252/
This commit is contained in:
Bill Kendrick 2022-07-03 17:18:58 -07:00
parent 844db56ab9
commit 06fafcb6d6
4 changed files with 112 additions and 1 deletions
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src/test-png.c Normal file
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/*
test-png.c
A tiny test program that opens a PNG file using libpng
library. If any warnings come back, this can help us tell
when any images include oddities that would cause Tux Paint
to echo warnings (via SDL_image->libpng) to stderr when it
goes to load them.
See https://sourceforge.net/p/tuxpaint/bugs/252/
Bill Kendrick <bill@newbreedsoftware.com>
(Based loosely on example code by Yoshimasa Niwa, https://gist.github.com/niw,
located at https://gist.github.com/niw/5963798, which itself was based on
code by Guillaume Cottenceau found at http://zarb.org/~gc/html/libpng.html)
2022-07-03 - 2022-07-03
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <png.h>
int main(int argc, char * argv[]) {
int i;
FILE * fi;
png_structp png;
png_infop info;
/* Usage output */
if (argc == 1 || strcmp(argv[1], "--help") == 0) {
fprintf(stderr, "Usage: %s file.png [file.png ...]\n", argv[0]);
exit(1);
}
/* Redirect stderr to stdout, so libpng's warnings can
be in the same stream as our's (where we report each
file's filename); allows more easily dumping to a file,
piping through `| less`, etc. */
dup2(STDOUT_FILENO, STDERR_FILENO);
/* Open each PNG image!... */
for (i = 1; i < argc; i++) {
printf("%5d ------------------------------------------------------------------\n", i);
printf("%s\n", argv[i]);
/* Open the file */
fi = fopen(argv[i], "rb");
if (fi == NULL) {
printf("Cannot open\n");
} else {
/* Prepare PNG library stuff... */
png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if (!png) {
fprintf(stderr, "Cannot png_create_read_struct()!\n");
exit(1);
}
info = png_create_info_struct(png);
if (!info) {
fprintf(stderr, "Cannot png_create_info_struct()!\n");
exit(1);
}
if (setjmp(png_jmpbuf(png))) {
fprintf(stderr, "Cannot setjmp(png_jmpbuf(png)))!\n");
exit(1);
}
/* Read the PNG's info */
png_init_io(png, fi);
png_read_info(png, info);
/* *** At this point, libpng would have reported issues *** */
/* (We could do additional things, like reporting image
dimensions, color depth, etc., but I don't see any reason to
care right now. -bjk 2022.07.03) */
/* Close and move on to the next file */
png_destroy_read_struct(&png, &info, NULL);
fclose(fi);
}
printf("\n");
fflush(stdout);
}
return(0);
}