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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> */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#include <errno.h>
+#include <string.h>
+#include <pixman.h>
+
+#include "cairo-test.h"
+
+#include "pdiff.h"
+#include "buffer-diff.h"
+
+/* Don't allow any differences greater than this value, even if pdiff
+ * claims that the images are identical */
+#define PERCEPTUAL_DIFF_THRESHOLD 25
+
+/* Compare two buffers, returning the number of pixels that are
+ * different and the maximum difference of any single color channel in
+ * result_ret.
+ *
+ * This function should be rewritten to compare all formats supported by
+ * cairo_format_t instead of taking a mask as a parameter.
+ */
+static void
+buffer_diff_core (const unsigned char *_buf_a, int stride_a,
+ const unsigned char *_buf_b, int stride_b,
+ unsigned char *_buf_diff, int stride_diff,
+ int width,
+ int height,
+ uint32_t mask,
+ buffer_diff_result_t *result_ret)
+{
+ const uint32_t *buf_a = (const uint32_t*) _buf_a;
+ const uint32_t *buf_b = (const uint32_t*) _buf_b;
+ uint32_t *buf_diff = (uint32_t*) _buf_diff;
+ int x, y;
+ buffer_diff_result_t result = {0, 0};
+
+ stride_a /= sizeof (uint32_t);
+ stride_b /= sizeof (uint32_t);
+ stride_diff /= sizeof (uint32_t);
+ for (y = 0; y < height; y++) {
+ const uint32_t *row_a = buf_a + y * stride_a;
+ const uint32_t *row_b = buf_b + y * stride_b;
+ uint32_t *row = buf_diff + y * stride_diff;
+
+ for (x = 0; x < width; x++) {
+ /* check if the pixels are the same */
+ if ((row_a[x] & mask) != (row_b[x] & mask)) {
+ int channel;
+ uint32_t diff_pixel = 0;
+
+ /* calculate a difference value for all 4 channels */
+ for (channel = 0; channel < 4; channel++) {
+ int value_a = (row_a[x] >> (channel*8)) & 0xff;
+ int value_b = (row_b[x] >> (channel*8)) & 0xff;
+ unsigned int diff;
+ diff = abs (value_a - value_b);
+ if (diff > result.max_diff)
+ result.max_diff = diff;
+ diff *= 4; /* emphasize */
+ if (diff)
+ diff += 128; /* make sure it's visible */
+ if (diff > 255)
+ diff = 255;
+ diff_pixel |= diff << (channel*8);
+ }
+
+ result.pixels_changed++;
+ if ((diff_pixel & 0x00ffffff) == 0) {
+ /* alpha only difference, convert to luminance */
+ uint8_t alpha = diff_pixel >> 24;
+ diff_pixel = alpha * 0x010101;
+ }
+ row[x] = diff_pixel;
+ } else {
+ row[x] = 0;
+ }
+ row[x] |= 0xff000000; /* Set ALPHA to 100% (opaque) */
+ }
+ }
+
+ *result_ret = result;
+}
+
+/* Compares two image surfaces
+ *
+ * Provides number of pixels changed and maximum single-channel
+ * difference in result.
+ *
+ * Also fills in a "diff" surface intended to visually show where the
+ * images differ.
+ */
+static void
+compare_surfaces (const cairo_test_context_t *ctx,
+ cairo_surface_t *surface_a,
+ cairo_surface_t *surface_b,
+ cairo_surface_t *surface_diff,
+ buffer_diff_result_t *result)
+{
+ /* These default values were taken straight from the
+ * perceptualdiff program. We'll probably want to tune these as
+ * necessary. */
+ double gamma = 2.2;
+ double luminance = 100.0;
+ double field_of_view = 45.0;
+ int discernible_pixels_changed;
+
+ /* First, we run cairo's old buffer_diff algorithm which looks for
+ * pixel-perfect images, (we do this first since the test suite
+ * runs about 3x slower if we run pdiff_compare first).
+ */
+ buffer_diff_core (cairo_image_surface_get_data (surface_a),
+ cairo_image_surface_get_stride (surface_a),
+ cairo_image_surface_get_data (surface_b),
+ cairo_image_surface_get_stride (surface_b),
+ cairo_image_surface_get_data (surface_diff),
+ cairo_image_surface_get_stride (surface_diff),
+ cairo_image_surface_get_width (surface_a),
+ cairo_image_surface_get_height (surface_a),
+ cairo_surface_get_content (surface_a) & CAIRO_CONTENT_ALPHA ? 0xffffffff : 0x00ffffff,
+ result);
+ if (result->pixels_changed == 0)
+ return;
+
+ cairo_test_log (ctx,
+ "%d pixels differ (with maximum difference of %d) from reference image\n",
+ result->pixels_changed, result->max_diff);
+
+ /* Then, if there are any different pixels, we give the pdiff code
+ * a crack at the images. If it decides that there are no visually
+ * discernible differences in any pixels, then we accept this
+ * result as good enough.
+ *
+ * Only let pdiff have a crack at the comparison if the max difference
+ * is lower than a threshold, otherwise some problems could be masked.
+ */
+ if (result->max_diff < PERCEPTUAL_DIFF_THRESHOLD) {
+ discernible_pixels_changed = pdiff_compare (surface_a, surface_b,
+ gamma, luminance, field_of_view);
+ if (discernible_pixels_changed == 0) {
+ result->pixels_changed = 0;
+ cairo_test_log (ctx,
+ "But perceptual diff finds no visually discernible difference.\n"
+ "Accepting result.\n");
+ }
+ }
+}
+
+void
+buffer_diff_noalpha (const unsigned char *buf_a,
+ const unsigned char *buf_b,
+ unsigned char *buf_diff,
+ int width,
+ int height,
+ int stride,
+ buffer_diff_result_t *result)
+{
+ buffer_diff_core(buf_a, stride,
+ buf_b, stride,
+ buf_diff, stride,
+ width, height,
+ 0x00ffffff,
+ result);
+}
+
+static cairo_bool_t
+same_size (cairo_surface_t *a, cairo_surface_t *b)
+{
+ unsigned int width_a, height_a;
+ unsigned int width_b, height_b;
+
+ width_a = cairo_image_surface_get_width (a);
+ height_a = cairo_image_surface_get_height (a);
+
+ width_b = cairo_image_surface_get_width (b);
+ height_b = cairo_image_surface_get_height (b);
+
+ return width_a == width_b && height_a == height_b;
+}
+
+/* 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.
+ *
+ * The return value simply indicates whether a check was successfully
+ * made, (as opposed to a file-not-found condition or similar). It
+ * does not indicate anything about how much the images differ. For
+ * that, see result.
+ *
+ * One failure mode is if the two images provided do not have the same
+ * dimensions. In this case, this function will return
+ * CAIRO_STATUS_SURFACE_TYPE_MISMATCH (which is a bit of an abuse, but
+ * oh well).
+ */
+cairo_status_t
+image_diff (const cairo_test_context_t *ctx,
+ cairo_surface_t *surface_a,
+ cairo_surface_t *surface_b,
+ cairo_surface_t *surface_diff,
+ buffer_diff_result_t *result)
+{
+ if (cairo_surface_status (surface_a))
+ return cairo_surface_status (surface_a);
+
+ if (cairo_surface_status (surface_b))
+ return cairo_surface_status (surface_b);
+
+ if (cairo_surface_status (surface_diff))
+ return cairo_surface_status (surface_diff);
+
+ if (! same_size (surface_a, surface_b) ||
+ ! same_size (surface_a, surface_diff))
+ {
+ cairo_test_log (ctx, "Error: Image size mismatch\n");
+ return CAIRO_STATUS_SURFACE_TYPE_MISMATCH;
+ }
+
+ compare_surfaces (ctx, surface_a, surface_b, surface_diff, result);
+
+ return CAIRO_STATUS_SUCCESS;
+}
+
+cairo_bool_t
+image_diff_is_failure (const buffer_diff_result_t *result,
+ unsigned int tolerance)
+{
+ return result->pixels_changed &&
+ result->max_diff > tolerance;
+}
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