1. An image enhancement system comprising a computer data processing system that includes at least one computer data hardware processor and other computer hardware components that, in connection with a modulation strength map (MSM) that contains positive or negative values representing a sign and magnitude of modulation to be applied in the vicinity of each of multiple locations in an image at each of multiple orientations for each of the locations, each of the multiple orientations at each of the multiple locations having an image value, collectively: generate a net signed fractional modulation value at each of the locations in the image using the MSM in combination with a modulation kernel F(θ), the generating being done in accordance with the following algorithm: at a given location X in the image, and for a given orientation θ, the modulation strength M represented in the MSM is used to scale F(θ); at every image location, positive and negative contributions are accumulated from all scaled modulation kernels arising from surrounding image locations/orientations, in order to produce a net signed fractional modulation value that represents a fractional increase or decrease to be applied to the image value at that location; and scale an image value at each location using the net signed fractional modulation value at each location, wherein application of the algorithm does not result in systematic clipping of peri-edge locations to maximum or minimum brightness values, or any other form of systematic homogenization of values at peri-edge locations.