cairo/test/imagediff.c

/* 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 <stdlib.h>

#include "buffer-diff.h"
#include "read-png.h"
#include "write-png.h"
#include "xmalloc.h"

int 
main (int argc, char *argv[])
{
    unsigned char *buffer_a;
    unsigned int width_a, height_a, stride_a;
    unsigned char *buffer_b;
    unsigned int width_b, height_b, stride_b;

    unsigned char *buffer;
    unsigned int width, height, stride;
    int buffer_size, total_pixels_changed;

    if (argc < 2) {
	fprintf (stderr, "Usage: %s image1.png image2.png\n", argv[0]);
	fprintf (stderr, "Computes an output image designed to present a \"visual diff\" such that even\n");
	fprintf (stderr, "small errors in single pixels are readily apparent in the output.\n");
	fprintf (stderr, "The output image is written on stdout.\n");
	exit (1);
    }

    read_png_argb32 (argv[1], &buffer_a, &width_a, &height_a, &stride_a);
    read_png_argb32 (argv[2], &buffer_b, &width_b, &height_b, &stride_b);

    if ((width_a == width_b) && (height_a == height_b) && (stride_a == stride_b))
    {
	width = width_a;
	height = height_a;
	stride = stride_a;
    } else {
	fprintf (stderr, "Error. Both images must be the same size\n");
	return 1;
    }

    buffer_size = stride * height;
    buffer = xmalloc (buffer_size);
    
    total_pixels_changed = buffer_diff (buffer_a, buffer_b, buffer,
					width_a, height_a, stride_a);


    if (total_pixels_changed)
	fprintf (stderr, "Total pixels changed: %d\n", total_pixels_changed);
    write_png_argb32 (buffer, stdout, width, height, stride);

    free (buffer);

    return total_pixels_changed;
}