Compare screenshots.

diff --git a/glretrace.py b/glretrace.py
index c74d88a..c516c16 100644 (file)
--- a/glretrace.py
+++ b/glretrace.py
@@ -162,7 +162,11 @@ bool __reshape_window = false;
 
 unsigned __frame = 0;
 long long __startTime = 0;
-bool __screenshots = 0;
+static enum {
+    MODE_DISPLAY = 0,
+    MODE_SCREENSHOT,
+    MODE_COMPARE,
+} __mode = MODE_DISPLAY;
 
 
 static void
@@ -224,12 +228,34 @@ static void display_noop(void) {
 static void frame_complete(void) {
     ++__frame;
     
-    if (__screenshots && !__reshape_window) {
+    if (!__reshape_window && (__mode == MODE_SCREENSHOT || __mode == MODE_COMPARE)) {
         char filename[PATH_MAX];
+
         snprintf(filename, sizeof filename, "screenshot_%04u.png", __frame);
-        Image::Image image(__window_width, __window_height, true);
-        glReadPixels(0, 0, __window_width, __window_height, GL_RGBA, GL_UNSIGNED_BYTE, image.pixels);
-        image.writePNG(filename);
+        
+        Image::Image *ref;
+        if (__mode == MODE_COMPARE) {
+            ref = Image::readPNG(filename);
+            if (!ref) {
+                return;
+            }
+            if (verbosity)
+                std::cout << "Read " << filename << "\n";
+        }
+        
+        Image::Image src(__window_width, __window_height, true);
+        glReadPixels(0, 0, __window_width, __window_height, GL_RGBA, GL_UNSIGNED_BYTE, src.pixels);
+
+        if (__mode == MODE_SCREENSHOT) {
+            if (src.writePNG(filename) && verbosity) {
+                std::cout << "Wrote " << filename << "\n";
+            }
+        }
+
+        if (__mode == MODE_COMPARE) {
+            std::cout << "Frame " << __frame << " average precision of " << src.compare(*ref) << " bits\n";
+            delete ref;
+        }
     }
 
 }
@@ -269,8 +295,12 @@ static void display(void) {
         " in " <<  timeInterval << " secs,"
         " average of " << (__frame/timeInterval) << " fps\n";
 
-    glutDisplayFunc(&display_noop);
-    glutIdleFunc(NULL);
+    if (__mode == MODE_DISPLAY) {
+        glutDisplayFunc(&display_noop);
+        glutIdleFunc(NULL);
+    } else {
+        exit(0);
+    }
 }
 
 static void idle(void) {
@@ -282,6 +312,17 @@ static void idle(void) {
     glutPostRedisplay();
 }
 
+static void usage(void) {
+    std::cout << 
+        "Usage: glretrace [OPTION] TRACE\n"
+        "Replay TRACE.\n"
+        "\n"
+        "  -c           compare against screenshots\n"
+        "  -db          use a double buffer visual\n"
+        "  -s           take snapshots\n"
+        "  -v           verbose output\n";
+}
+
 int main(int argc, char **argv)
 {
 
@@ -295,14 +336,20 @@ int main(int argc, char **argv)
 
         if (!strcmp(arg, "--")) {
             break;
+        } else if (!strcmp(arg, "-c")) {
+            __mode = MODE_COMPARE;
         } else if (!strcmp(arg, "-db")) {
             double_buffer = true;
+        } else if (!strcmp(arg, "--help")) {
+            usage();
+            return 0;
         } else if (!strcmp(arg, "-s")) {
-            __screenshots = true;
+            __mode = MODE_SCREENSHOT;
         } else if (!strcmp(arg, "-v")) {
             ++verbosity;
         } else {
             std::cerr << "error: unknown option " << arg << "\n";
+            usage();
             return 1;
         }
     }

diff --git a/image.cpp b/image.cpp
index ce37c19..9fd1dc8 100644 (file)
--- a/image.cpp
+++ b/image.cpp
@@ -26,6 +26,7 @@
 
 #include <png.h>
 
+#include <math.h>
 #include <stdint.h>
 
 #include <fstream>
@@ -273,4 +274,37 @@ 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*4; ++x) {
+            int delta = pSrc[x] - pRef[x];
+            error += delta*delta;
+        }
+
+        pSrc += stride();
+        pRef += ref.stride();
+    }
+
+    double numerator = error*2 + 1;
+    double denominator = height*width*4ULL*255ULL*255ULL*2;
+    double quotient = numerator/denominator;
+
+    // Precision in bits
+    double precision = -log(quotient)/log(2.0);
+
+    return precision;
+}
+
+
+
 } /* namespace Image */

diff --git a/image.hpp b/image.hpp
index e1919d6..5a9704e 100644 (file)
--- a/image.hpp
+++ b/image.hpp
@@ -59,8 +59,22 @@ public:
         delete [] pixels;
     }
 
+    inline unsigned char *start(void) {
+        return flipped ? pixels + (height - 1)*width*4 : pixels;
+    }
+
+    inline unsigned char *end(void) {
+        return flipped ? pixels - width*4 : pixels + height*width*4;
+    }
+
+    inline signed stride(void) const {
+        return flipped ? -width*4 : width*4;
+    }
+
     bool writeBMP(const char *filename) const;
     bool writePNG(const char *filename) const;
+
+    double compare(Image &ref);
 };