add max histogram

naixx · May 22, 2017 · 42273f9 · 42273f9
1 parent 478192f
commit 42273f9
Showing 1 changed file with 20 additions and 6 deletions.
diff --git a/lib/jpeg-lum.cc b/lib/jpeg-lum.cc
@@ -6,9 +6,10 @@
 #include <math.h>
 
 unsigned int size;
-unsigned int histogram[256];
+unsigned int histogram[3][256];
 unsigned int width;
 unsigned int height;
+unsigned long count;
 double luminance;
 double pixel;
 double clipped;
@@ -98,21 +99,21 @@ int read_jpeg_file(char *filename)
   height = cinfo.output_height;
   luminance = 0.0;
   size = cinfo.output_width*cinfo.output_height*cinfo.num_components*sizeof(unsigned int);
-  memset(histogram, 0, sizeof(int)*256);
+  memset(histogram, 0, sizeof(int)*256*3);
   row_pointer[0] = (unsigned char *)malloc(cinfo.output_width*cinfo.num_components);
-  unsigned long count = 0;
+  count = 0;
   while (cinfo.output_scanline < cinfo.image_height) {
       jpeg_read_scanlines( &cinfo, row_pointer, 1 );
       for (i=0; i<cinfo.image_width;i+=cinfo.num_components) {
           pixel = 0.0;
           for(component=0;component<cinfo.num_components;component++) {
-              if(component < 2) {
+              if(component < 3) {
                   pixel = (double) row_pointer[0][i + component];
                   pixel = lum(pixel);
                   if(pixel > 4) clipped++;
                   luminance += pixel;
                   count++;
-//          histogram[(int)pixel]++;
+                  histogram[component][(int)pixel]++;
               }
           }
       }
@@ -140,8 +141,21 @@ Handle<Value> CreateObject(const FunctionCallbackInfo<Value>& info) {
 
   Local<Object> obj = Object::New(isolate);
   Local<Array> histArray = Array::New(isolate, 256);
+
+  unsigned int maxPeak = 0;
+  for (unsigned int i = 0; i < 256; i++) {
+    for(unsigned int j = 0; j < 3; j++) {
+      if(histogram[j][i] > maxPeak) maxPeak = histogram[j][i];
+    }
+  }
+
   for (unsigned int i = 0; i < 256; i++) {
-    histArray->Set(i, Number::New(isolate, histogram[i]));
+    unsigned int max = 0;
+    for(unsigned int j = 0; j < 3; j++) {
+      if(histogram[j][i] > max) max = histogram[j][i];
+    }
+    max = (max*16)/((maxPeak*16)/256); // compress to 256 max, integer math for speed
+    histArray->Set(i, Number::New(isolate, max));
   }
 
   obj->Set(String::NewFromUtf8(isolate, "histogram", String::kInternalizedString), histArray);