Various embodiments of the present invention are directed to methods and systems for processing signals, particularly signals encoding two-dimensional images, such as photographs, video frames, graphics, and other visually displayed information. In various method embodiments of the present invention, an input image signal is decomposed into an upper-envelope function, a lower-envelope function, and a details function. One or both of the upper-envelope and lower-envelope functions are then modified to produce one or more image-enhancing effects when the modified upper-envelope and lower-envelope functions are recombined with the details function to produce an enhanced image signal.