diff --git a/lib/frame_grabber.js b/lib/frame_grabber.js
index 3d7d132..9607389 100644
--- a/lib/frame_grabber.js
+++ b/lib/frame_grabber.js
@@ -15,17 +15,23 @@ define(["cv_utils"], function(CVUtils) {
             _video_size = CVUtils.imageRef(inputStream.getRealWidth(), inputStream.getRealHeight()),
             _canvasSize = inputStream.getCanvasSize(),
             _size = CVUtils.imageRef(inputStream.getWidth(), inputStream.getHeight()),
-            topRight = inputStream.getTopRight(),
+            _topRight = inputStream.getTopRight(),
             _data = new Uint8Array(_size.x * _size.y),
             _grayData = new Uint8Array(_video_size.x * _video_size.y),
-            _canvasData = new Uint8Array(_canvasSize.x * _canvasSize.y);
+            _canvasData = new Uint8Array(_canvasSize.x * _canvasSize.y),
+            _grayImageArray = Ndarray(_grayData, [_video_size.y, _video_size.x]).transpose(1, 0),
+            _canvasImageArray = Ndarray(_canvasData, [_canvasSize.y, _canvasSize.x]).transpose(1, 0),
+            _targetImageArray = _canvasImageArray.hi(_topRight.x + _size.x, _topRight.y + _size.y).lo(_topRight.x, _topRight.y),
+            _stepSizeX = _video_size.x/_canvasSize.x,
+            _stepSizeY = _video_size.y/_canvasSize.y;
 
         console.log("FrameGrabber", JSON.stringify({
-            size: _size,
-            topRight: topRight,
-            videoSize: _video_size,
-            canvasSize: _canvasSize
-        }));
+            videoSize: _grayImageArray.shape,
+            canvasSize: _canvasImageArray.shape,
+            stepSize: [_stepSizeX, _stepSizeY],
+            size: _targetImageArray.shape,
+            topRight: _topRight
+        }, null, 2));
 
         /**
          * Uses the given array as frame-buffer
@@ -46,51 +52,40 @@ define(["cv_utils"], function(CVUtils) {
          * The image-data is converted to gray-scale and then half-sampled if configured.
          */
         _that.grab = function() {
-            var doHalfSample = _streamConfig.halfSample,
-                frame = inputStream.getFrame();
+            var frame = inputStream.getFrame();
 
             if (frame) {
-                this.scaleAndCrop(frame, _video_size, _canvasSize, topRight, _size);
+                this.scaleAndCrop(frame);
                 return true;
             } else {
                 return false;
             }
         };
 
-        _that.scaleAndCrop = function(frame, frameSize, canvasSize, topRight, targetSize) {
-            var grayImageArray = Ndarray(_grayData, [frameSize.y, frameSize.x]).transpose(1, 0),
-                canvasImageArray = Ndarray(_canvasData, [canvasSize.y, canvasSize.x]).transpose(1, 0),
-                targetImageArray = canvasImageArray.hi(topRight.x + targetSize.x, topRight.y + targetSize.y).lo(topRight.x, topRight.y),
-                stepSizeX = frameSize.x/canvasSize.x,
-                stepSizeY = frameSize.y/canvasSize.y,
-                x,
+        _that.scaleAndCrop = function(frame) {
+            var x,
                 y;
 
-            console.log("Input-size: ", grayImageArray.shape);
-            console.log("Canvas-size: ", canvasImageArray.shape);
-            console.log("Target-size: ", targetImageArray.shape);
-
-            console.log("Step-size: ", [stepSizeX, stepSizeY]);
-
             // 1. compute full-sized gray image
             CVUtils.computeGray(frame.data, _grayData);
 
             // 2. interpolate
-            for (y = 0; y < canvasSize.y; y++) {
-                for (x = 0; x < canvasSize.x; x++) {
-                    canvasImageArray.set(x, y, (Interp2D(grayImageArray, x*stepSizeX, y*stepSizeY)) | 0);
+            for (y = 0; y < _canvasSize.y; y++) {
+                for (x = 0; x < _canvasSize.x; x++) {
+                    _canvasImageArray.set(x, y, (Interp2D(_grayImageArray, x * _stepSizeX, y * _stepSizeY)) | 0);
                 }
             }
 
             // targetImageArray must be equal to targetSize
-            if (targetImageArray.shape[0] !== targetSize.x ||
-                targetImageArray.shape[1] !== targetSize.y) {
+            if (_targetImageArray.shape[0] !== _size.x ||
+                _targetImageArray.shape[1] !== _size.y) {
                 throw new Error("Shapes do not match!");
             }
+
             // 3. crop
-            for (y = 0; y < targetSize.y; y++) {
-                for (x = 0; x < targetSize.x; x++) {
-                    _data[y*targetSize.x + x] = targetImageArray.get(x, y);
+            for (y = 0; y < _size.y; y++) {
+                for (x = 0; x < _size.x; x++) {
+                    _data[y * _size.x + x] = _targetImageArray.get(x, y);
                 }
             }
         },