public Rect scalePreview(Size previewSize, Size viewfinderSize) {
        return new Rect(0, 0, viewfinderSize.width, viewfinderSize.height);
    }
Scale the preview to match the viewfinder exactly.

@param previewSize the size of the preview (camera), in current display orientation
@param viewfinderSize the size of the viewfinder (display), in current display orientation
@return a rect placing the preview
zxing-android-embedded/src/com/journeyapps/barcodescanner/camera/FitXYStrategy.java