Report # of pixels and max difference when there are image differences.

3 files changed, 34 insertions, 23 deletions

diff --git a/buffer-diff.c b/buffer-diff.c
index cbfe986..f0d2d18 100644
--- a/buffer-diff.c
+++ b/buffer-diff.c
@@ -32,7 +32,7 @@
 #include "util.h"
 #include "read-cache.h"
 
-int
+struct diff_results
 buffer_diff (unsigned char *buf_a,
 	     unsigned char *buf_b,
 	     unsigned char *buf_diff,
@@ -42,7 +42,7 @@ buffer_diff (unsigned char *buf_a,
 {
     int x, y;
     unsigned char *row_a, *row_b, *row;
-    int pixels_changed = 0;
+    struct diff_results results  = { .pixels_changed = 0, .max_difference = 0 };
 
     for (y = 0; y < height; y++)
     {
@@ -67,19 +67,21 @@ buffer_diff (unsigned char *buf_a,
 		    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) {
-		pixels_changed++;
+		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 pixels_changed;
+    return results;
 }
 
 static int copy_file(const char *filename_a, const char *filename_b)
@@ -99,13 +101,13 @@ static int copy_file(const char *filename_a, const char *filename_b)
   return 0;
 }
 
-int
+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)
 {
-    int pixels_changed;
+    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;
@@ -114,7 +116,7 @@ image_buf_diff (void *buf, int width_a, int height_a, int stride_a,
     if (cache_compare(filename_b, buf_a, height_a * stride_a)) {
       if (copy_file(filename_b, filename_a) == 0) {
 	xunlink (filename_diff);
-	return 0;
+	return results;
       }
     }
 
@@ -139,10 +141,10 @@ image_buf_diff (void *buf, int width_a, int height_a, int stride_a,
 
     buf_diff = xcalloc (stride_a * height_a, 1);
 
-    pixels_changed = buffer_diff (buf_a, buf_b, buf_diff,
+    results = buffer_diff (buf_a, buf_b, buf_diff,
 				  width_a, height_a, stride_a);
 
-    if (pixels_changed) {
+    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);
@@ -157,7 +159,7 @@ image_buf_diff (void *buf, int width_a, int height_a, int stride_a,
     free (buf_b);
     free (buf_diff);
 
-    return pixels_changed;
+    return results;
 
 fail:
     {
@@ -165,10 +167,11 @@ fail:
 	FILE *png_file = fopen (filename_a, "wb");
 	write_png_argb32 (buf_a, png_file, width_a, height_a, stride_a);
 	fclose (png_file);
-	return -1;
+	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
@@ -229,3 +232,4 @@ image_diff (const char *filename_a,
 
     return pixels_changed;
 }
+#endif
diff --git a/buffer-diff.h b/buffer-diff.h
index a37fdc5..54034d5 100644
--- a/buffer-diff.h
+++ b/buffer-diff.h
@@ -26,11 +26,16 @@
 #ifndef BUFFER_DIFF_H
 #define BUFFER_DIFF_H
 
+struct diff_results {
+    int pixels_changed;
+    int max_difference;
+};
+
 /* Returns number of pixels changed, (or -1 on error).
  * Also fills in a "diff" buffer intended to visually show where the
  * images differ.
  */
-int
+struct diff_results
 buffer_diff (unsigned char *buf_a,
 	     unsigned char *buf_b,
 	     unsigned char *buf_diff,
@@ -38,7 +43,7 @@ buffer_diff (unsigned char *buf_a,
 	     int	    height,
 	     int	    stride);
 
-int
+struct diff_results
 image_buf_diff (void *buf_a, int width_a, int height_a, int stride_a,
 	    const char *filename_a,
 	    const char *filename_b,
diff --git a/test-poppler.c b/test-poppler.c
index f9f2aed..24e462b 100644
--- a/test-poppler.c
+++ b/test-poppler.c
@@ -49,11 +49,11 @@ int ilog10(int a)
   return log;
 }
 
-poppler_test_status_t gdk_pixbuf_compare(GdkPixbuf *pixbuf, char *page_name)
+struct diff_results gdk_pixbuf_compare(GdkPixbuf *pixbuf, char *page_name)
 {
   char *png_name, *ref_name, *diff_name;
   char *srcdir;
-  int pixels_changed;
+  struct diff_results results;
   const char *backend = poppler_get_backend() == POPPLER_BACKEND_SPLASH ? "splash" : "cairo";
    /* Get the strings ready that we'll need. */
   srcdir = getenv ("srcdir");
@@ -80,14 +80,14 @@ poppler_test_status_t gdk_pixbuf_compare(GdkPixbuf *pixbuf, char *page_name)
     }
   }
 
-  pixels_changed = image_buf_diff (cairo_pixels, width, height, width*4, png_name, ref_name, diff_name);
+  results = image_buf_diff (cairo_pixels, width, height, width*4, png_name, ref_name, diff_name);
 
   free (cairo_pixels);
   free (png_name);
   free (ref_name);
   free (diff_name);
 
-  return pixels_changed ? POPPLER_TEST_FAILURE : POPPLER_TEST_SUCCESS;
+  return results;
 }
 
 PopplerPSFile *poppler_ps_file_new            (PopplerDocument *document,
@@ -188,7 +188,7 @@ poppler_test_status_t poppler_test_page_text(PopplerPage *page, char *text_name)
   return ret;
 }
 
-poppler_test_status_t poppler_test_page(char *pdf_file, PopplerDocument *document, int page_index, int n_pages) {
+poppler_test_status_t poppler_test_page(char *pdf_file, PopplerDocument *document, int page_index, int n_pages, struct diff_results *results) {
   GdkPixbuf *pixbuf, *thumb;
   double width, height;
   PopplerPage *page;
@@ -212,14 +212,15 @@ poppler_test_status_t poppler_test_page(char *pdf_file, PopplerDocument *documen
   pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8, width, height);
   poppler_page_render_to_pixbuf (page, 0, 0, width, height, 1.0, 0, pixbuf);
 
-  ret = gdk_pixbuf_compare(pixbuf, page_name);
+  *results = gdk_pixbuf_compare(pixbuf, page_name);
+  ret = results->pixels_changed ? POPPLER_TEST_FAILURE : POPPLER_TEST_SUCCESS;
 
   if (text_output)
     ret |= poppler_test_page_text(page, text_name);
 
   thumb = poppler_page_get_thumbnail(page);
   if (thumb)
-    ret |= gdk_pixbuf_compare(thumb, thumb_name);
+    ret |= gdk_pixbuf_compare(thumb, thumb_name).pixels_changed ? POPPLER_TEST_FAILURE : POPPLER_TEST_SUCCESS;
  
   if (thumb)
     g_object_unref (G_OBJECT (thumb));
@@ -251,10 +252,11 @@ void poppler_test(char *pdf_file)
   int i;
   int n_pages = poppler_document_get_n_pages(document);
   for (i=0; i<n_pages; i++) {
+    struct diff_results results;
     printf("%s-%d ", pdf_file, i);
     fflush(stdout);
-    if (poppler_test_page(pdf_file, document, i, n_pages))
-      printf("FAIL\n");
+    if (poppler_test_page(pdf_file, document, i, n_pages, &results))
+      printf("FAIL (%d %d)\n", results.pixels_changed, results.max_difference);
     else
       printf("PASS\n");
   }