1. A signal-processing system comprising: a processing component; and a signal-processing routine executed by the processing component that enhances an input image to produce an enhanced output image and store the output image in an electronic memory by computing, by constructing multi-scale intermediate-image pyramids, a photographic-mask, without low-contrast details, in which smooth, homogeneous regions are separated by high-contrast edges, and a temporary-image with enhanced mid-contrast detail, retained high-contrast detail, and reduced low-contrast detail, and employing values of the photographic-mask intermediate image and temporary-image intermediate image to produce the output image that is stored in the electronic memory and that is globally and locally contrast-enhanced, sharpened, and denoised, with global contrast enhancements including one or more of brightening, darkening, histogram stretching or equalization, and gamma correction and local contrast enhancements including one or more of adaptive lighting, shadow lighting, highlight enhancement, and 3D boosting.