X-Git-Url: https://git.cworth.org/git?a=blobdiff_plain;f=image.cpp;h=937f486bfbc01cbe3676b54ce67be52f84b1a754;hb=52eaaa2f3749692d587a41145da900f9014e9002;hp=ce37c190c097cff6a624d4870e9dca5a58adfad3;hpb=4cebb746f86d7ff67d816e15a68921885c2958c9;p=apitrace

diff --git a/image.cpp b/image.cpp
index ce37c19..937f486 100644
--- a/image.cpp
+++ b/image.cpp
@@ -26,6 +26,7 @@
 
 #include <png.h>
 
+#include <math.h>
 #include <stdint.h>
 
 #include <fstream>
@@ -164,7 +165,7 @@ Image::writePNG(const char *filename) const {
     png_set_IHDR(png_ptr, info_ptr, width, height, 8, PNG_COLOR_TYPE_RGB_ALPHA,
         PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
 
-    png_set_compression_level(png_ptr, Z_BEST_COMPRESSION);
+    png_set_compression_level(png_ptr, Z_DEFAULT_COMPRESSION);
 
     png_write_info(png_ptr, info_ptr);
 
@@ -273,4 +274,41 @@ no_fp:
 }
 
 
+double Image::compare(Image &ref)
+{
+    if (width != ref.width ||
+        height != ref.height) {
+        return 0.0;
+    }
+
+    const unsigned char *pSrc = start();
+    const unsigned char *pRef = ref.start();
+
+    unsigned long long error = 0;
+    for (unsigned y = 0; y < height; ++y) {
+        for (unsigned  x = 0; x < width; ++x) {
+            // FIXME: Ignore alpha channel until we are able to pick a visual
+            // that matches the traces
+            for (unsigned  c = 0; c < 3; ++c) {
+                int delta = pSrc[x*4 + c] - pRef[x*4 + c];
+                error += delta*delta;
+            }
+        }
+
+        pSrc += stride();
+        pRef += ref.stride();
+    }
+
+    double numerator = error*2 + 1;
+    double denominator = height*width*3ULL*255ULL*255ULL*2;
+    double quotient = numerator/denominator;
+
+    // Precision in bits
+    double precision = -log(quotient)/log(2.0);
+
+    return precision;
+}
+
+
+
 } /* namespace Image */