diff --git a/flake.nix b/flake.nix
index 8a034a4..42819c2 100644
--- a/flake.nix
+++ b/flake.nix
@@ -35,14 +35,14 @@
 
           nativeBuildInputs = with pkgs; [
             cmake
-            opencv2
+            opencv3
             liblbfgs
             qt5.full
             libsForQt5.qt5.wrapQtAppsHook
           ];
 
           configurePhase = ''
-            cmake scannerExtract -DCMAKE_BUILD_TYPE=release -DOPENCV2=1
+            cmake scannerExtract -DCMAKE_BUILD_TYPE=release
           '';
 
           buildPhase = ''
@@ -90,7 +90,7 @@
       default = pkgs.mkShellNoCC {
         packages = with pkgs; [
           cmake
-          opencv2
+          opencv3
           liblbfgs
           gt5.full
 
diff --git a/scannerExtract/preloadsource.cpp b/scannerExtract/preloadsource.cpp
index 2504639..98034c5 100644
--- a/scannerExtract/preloadsource.cpp
+++ b/scannerExtract/preloadsource.cpp
@@ -194,14 +194,20 @@ void PreloadSource::getSumOfRectangleSampling(const QVector<cv::Point2f> pts,
     sumValues = 0;
     numPixels = 0;
 
-    IplImage tmp = image;
+    IplImage tmp = cvIplImage(image);
     assert(image.type() == CV_8U);
 
     for (int i=0; i<4; i++)
     {
 
         CvLineIterator iterator;
-        const int count = cvInitLineIterator( &tmp, pts[i], pts[(i+1)%4], &iterator, 4);
+        const int count = cvInitLineIterator(
+            &tmp,
+            cvPoint(cvRound(pts[i].x), cvRound(pts[i].y)),
+            cvPoint(cvRound(pts[(i + 1) % 4].x), cvRound(pts[(i + 1) % 4].y)),
+            &iterator,
+            4
+        );
 
         for( int j = 0; j < count; j++ ){
             sumValues += iterator.ptr[0];