When frame is rendered to file, bilinear interpolation on scaled images
caused blurred edges.

This is fixed by not doing interpolation with pixels outside of source
buffer.

Such fix doesn't cover cropped images which are currently cropped by
filling area of image with black transparent color, because image buffer
has bigger size than visible image area.

This is fixed by offsetting range used in previous fix by amount, that
would correspond to crop distance. Because of this, image area doesn't
even need to be filled with transparency.