Figure 4From: A framework for measuring sharpness in natural images captured by digital cameras based on reference image and local areasThe centers of the correspondence blocks are approximated from the correspondence feature points. (a) The reference and (b) test images have been cropped using the same pixel coordinate values. The lines denote vectors whose lengths and directions are calculated from the reference image. The points denote correspondence-feature points. The crosses denote correspondence-area centers.Back to article page