Add absolute frame difference module

modules/FrameDifference.cpp

@@ -23,6 +23,7 @@
  */
 
 #include "FrameDifference.h"
+#include <algorithm>
 
 namespace plaYUVer
 {
@@ -32,7 +33,7 @@ static PlaYUVerModuleDefinition FrameDifferenceDef =
     FRAME_PROCESSING_MODULE,
     "Measurements",
     "AbsoluteFrameDifference",
-    "Measure the difference between two images (Y plane), e. g., abs( Y1 - Y2 )",
+    "Measure the difference between two images (Y plane),  Y1 - Y2, with max absolute diff of 128",
     MODULE_REQUIRES_TWO_FRAMES,
     MODULE_REQUIRES_NEW_WINDOW,
     APPLY_WHILE_PLAYING,
@@ -55,13 +56,17 @@ PlaYUVerFrame* FrameDifference::process( PlaYUVerFrame* Input1, PlaYUVerFrame* I
   Pel* pInput2PelYUV = Input2->getPelBufferYUV()[0][0];
   Pel* pOutputPelYUV = m_pcFrameDifference->getPelBufferYUV()[0][0];
   Int aux_pel_1, aux_pel_2;
+  Int diff = 0;
 
   for( UInt y = 0; y < m_pcFrameDifference->getHeight(); y++ )
     for( UInt x = 0; x < m_pcFrameDifference->getWidth(); x++ )
     {
       aux_pel_1 = *pInput1PelYUV++;
       aux_pel_2 = *pInput2PelYUV++;
-      *pOutputPelYUV++ = abs( aux_pel_1 - aux_pel_2 );
+      diff = aux_pel_1 - aux_pel_2;
+      diff = std::min( diff, 127 );
+      diff = std::max( diff, -128 );
+      *pOutputPelYUV++ = diff;
     }
   return m_pcFrameDifference;
 }