Initial revision

1 files changed, 149 insertions, 0 deletions

diff --git a/buffer-diff.c b/buffer-diff.c
new file mode 100644
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+++ b/buffer-diff.c
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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 <unistd.h>
+#include <errno.h>
+#include <string.h>
+
+#include "buffer-diff.h"
+#include "read-png.h"
+#include "write-png.h"
+#include "xmalloc.h"
+
+static void
+xunlink (const char *pathname)
+{
+    if (unlink (pathname) < 0 && errno != ENOENT) {
+	fprintf (stderr, "  Error: Cannot remove %s: %s\n",
+		 pathname, strerror (errno));
+	exit (1);
+    }
+}
+
+int
+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;
+    int pixels_changed = 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;
+	    unsigned char value_a, value_b;
+	    int pixel_differs = 0;
+	    for (channel = 0; channel < 4; channel++)
+	    {
+		double diff;
+		value_a = row_a[x * 4 + channel];
+		value_b = row_b[x * 4 + channel];
+		if (value_a != value_b)
+		    pixel_differs = 1;
+		diff = value_a - value_b;
+		row[x * 4 + channel] = 128 + diff / 3.0;
+	    }
+	    if (pixel_differs) {
+		pixels_changed++;
+	    } else {
+		row[x*4+0] = 0;
+		row[x*4+1] = 0;
+		row[x*4+2] = 0;
+	    }
+	    row[x * 4 + 3] = 0xff; /* Set ALPHA to 100% (opaque) */
+	}
+    }
+
+    return pixels_changed;
+}
+
+/* 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)
+	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;
+}