From 6ddb7981771b8783fad32bfd56f0414200fce97f Mon Sep 17 00:00:00 2001
From: Jan Philipp Timme <jan.philipp@timme.it>
Date: Fri, 11 Dec 2015 14:47:16 +0100
Subject: [PATCH] [TASK] Fix contrast calculation.

---
 lazy_image.cpp | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/lazy_image.cpp b/lazy_image.cpp
index 432c163..08adc57 100644
--- a/lazy_image.cpp
+++ b/lazy_image.cpp
@@ -65,21 +65,16 @@ class LazyImage {
       for(int i=0; i<256;i++) {
 	sum += (i*histogramm_relative_intensity[i]);
       }
-      this->intensity_average = (int) qRound(sum);
+      this->intensity_average = qRound(sum);
     };
 
     void calcIntensityVariance(void) {
       int intensity_average = this->intensity_average;
-      int sum_difference = 0;
-      for(int x=0; x<this->img->width(); x++) {
-	for(int y=0; y<this->img->height(); y++) {
-	  QColor color = QColor::fromRgb(this->img->pixel(x, y));
-	  int r,g,b;
-	  color.getRgb(&r,&g,&b);
-	  sum_difference += std::abs(this->calcIntensity(r, g, b) - intensity_average);;
-	}
+      double sum = 0;
+      for(int i=0; i<256; i++) {
+	sum += histogramm_relative_intensity[i] * pow((i - intensity_average),2);
       }
-      this->intensity_variance = (int) qRound(sum_difference/(this->img->width()*this->img->height()));
+      this->intensity_variance = qRound(sum);
     };
     
     void generateNormalHistogrammImage(void) {