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/* imagediff - Compare two images
*
* Copyright © 2004 Richard D. Worth
*
* Permission to use, copy, modify, distribute, and sell this software
* and its documentation for any purpose is hereby granted without
* fee, provided that the above copyright notice appear in all copies
* and that both that copyright notice and this permission notice
* appear in supporting documentation, and that the name of Richard Worth
* not be used in advertising or publicity pertaining to distribution
* of the software without specific, written prior permission.
* Richard Worth makes no representations about the suitability of this
* software for any purpose. It is provided "as is" without express
* or implied warranty.
*
* RICHARD WORTH DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
* NO EVENT SHALL RICHARD WORTH BE LIABLE FOR ANY SPECIAL, INDIRECT OR
* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
* OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
* NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* Author: Richard D. Worth <richard@theworths.org> */
#include <stdio.h>
#include <stdint.h>
#include "buffer-diff.h"
#include "read-png.h"
#include "write-png.h"
#include "util.h"
#include "read-cache.h"
struct diff_results
buffer_diff (unsigned char *buf_a,
unsigned char *buf_b,
unsigned char *buf_diff,
int width,
int height,
int stride)
{
int x, y;
unsigned char *row_a, *row_b, *row;
struct diff_results results = { .pixels_changed = 0, .max_difference = 0 };
for (y = 0; y < height; y++)
{
row_a = buf_a + y * stride;
row_b = buf_b + y * stride;
row = buf_diff + y * stride;
for (x = 0; x < width; x++)
{
int channel;
uint32_t value_a, value_b;
int pixel_differs = 0;
//XXX: it looks like this might overread...
value_a = *(uint32_t*)(&(row_a[x*4]));
value_b = *(uint32_t*)(&(row_b[x*4]));
if (value_a != value_b) {
for (channel = 0; channel < 4; channel++)
{
double diff;
unsigned char channel_value_a, channel_value_b;
channel_value_a = row_a[x * 4 + channel];
channel_value_b = row_b[x * 4 + channel];
if (channel_value_a != channel_value_b) {
pixel_differs = 1;
diff = channel_value_a - channel_value_b;
if (diff > results.max_difference)
results.max_difference = diff;
row[x * 4 + channel] = 128 + diff / 3.0;
}
}
}
if (pixel_differs) {
results.pixels_changed++;
*(uint32_t*)(&(row[x*4])) |= 0xff000000; /* Set ALPHA to 100% (opaque) */
} else {
*(uint32_t*)(&(row[x*4])) = 0xff000000; /* Set ALPHA to 100% (opaque) */
}
}
}
return results;
}
static int copy_file(const char *filename_a, const char *filename_b)
{
char buf[4096];
FILE *filea = fopen(filename_a, "r");
FILE *fileb = fopen (filename_b, "wb");
if (!filea || !fileb)
return -1;
int count = sizeof(buf);
while (count == sizeof(buf)) {
count = fread(buf, 1, sizeof(buf), filea);
fwrite(buf, 1, count, fileb);
}
fclose(filea);
fclose(fileb);
return 0;
}
struct diff_results
image_buf_diff (void *buf, int width_a, int height_a, int stride_a,
const char *filename_a,
const char *filename_b,
const char *filename_diff)
{
struct diff_results results = { .pixels_changed = 0 };
unsigned int width_b, height_b, stride_b;
unsigned char *buf_b, *buf_diff;
unsigned char *buf_a = buf;
read_png_status_t status;
if (cache_compare(filename_b, buf_a, height_a * stride_a)) {
if (copy_file(filename_b, filename_a) == 0) {
xunlink (filename_diff);
return results;
}
}
status = read_png_argb32 (filename_b, &buf_b, &width_b, &height_b, &stride_b);
if (status) {
goto fail;
}
if (width_a != width_b ||
height_a != height_b ||
stride_a != stride_b)
{
fprintf (stderr,
"Error: Image size mismatch: (%dx%d@%d) vs. (%dx%d@%d)\n"
" for %s vs. %s\n",
width_a, height_a, stride_a,
width_b, height_b, stride_b,
filename_a, filename_b);
free (buf_b);
goto fail;
}
buf_diff = xcalloc (stride_a * height_a, 1);
results = buffer_diff (buf_a, buf_b, buf_diff,
width_a, height_a, stride_a);
if (results.pixels_changed) {
FILE *png_file = fopen (filename_diff, "wb");
write_png_argb32 (buf_diff, png_file, width_a, height_a, stride_a);
fclose (png_file);
png_file = fopen (filename_a, "wb");
write_png_argb32 (buf_a, png_file, width_a, height_a, stride_a);
fclose (png_file);
} else {
copy_file(filename_b, filename_a);
xunlink (filename_diff);
}
free (buf_b);
free (buf_diff);
return results;
fail:
{
// write out the buffer on failure
FILE *png_file = fopen (filename_a, "wb");
write_png_argb32 (buf_a, png_file, width_a, height_a, stride_a);
fclose (png_file);
results.pixels_changed = -1;
return results;
}
}
#if 0
/* Image comparison code courtesy of Richard Worth <richard@theworths.org>
* Returns number of pixels changed, (or -1 on error).
* Also saves a "diff" image intended to visually show where the
* images differ.
*/
int
image_diff (const char *filename_a,
const char *filename_b,
const char *filename_diff)
{
int pixels_changed;
unsigned int width_a, height_a, stride_a;
unsigned int width_b, height_b, stride_b;
unsigned char *buf_a, *buf_b, *buf_diff;
read_png_status_t status;
status = read_png_argb32 (filename_a, &buf_a, &width_a, &height_a, &stride_a);
if (status)
return -1;
status = read_png_argb32 (filename_b, &buf_b, &width_b, &height_b, &stride_b);
if (status) {
free (buf_a);
return -1;
}
if (width_a != width_b ||
height_a != height_b ||
stride_a != stride_b)
{
fprintf (stderr,
"Error: Image size mismatch: (%dx%d@%d) vs. (%dx%d@%d)\n"
" for %s vs. %s\n",
width_a, height_a, stride_a,
width_b, height_b, stride_b,
filename_a, filename_b);
free (buf_a);
free (buf_b);
return -1;
}
buf_diff = xcalloc (stride_a * height_a, 1);
pixels_changed = buffer_diff (buf_a, buf_b, buf_diff,
width_a, height_a, stride_a);
if (pixels_changed) {
FILE *png_file = fopen (filename_diff, "wb");
write_png_argb32 (buf_diff, png_file, width_a, height_a, stride_a);
fclose (png_file);
} else {
xunlink (filename_diff);
}
free (buf_a);
free (buf_b);
free (buf_diff);
return pixels_changed;
}
#endif
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