Abstract: A block transform image processing method employs singular value decomposition to reduce noise without affecting texture and edge detail. A nonlinear gain function based on the measured statistics of the singular values for image noise is generated. The image is filtered to produce a detail image and a low pass filtered image. The detail image is divided into blocks and the blocks are transformed to produce singular vectors and arrays of singular values. The nonlinear gain function is applied to the arrays of singular values and an inverse SVD transform is applied to the modified singular values to produce a processed detail image. The processed detail image is combined with the low pass filtered image to produce a processed image having reduced noise.

Abstract: A method of determining the color of light employed to illuminate the scene in a color image from the image itself, relies upon detecting the color of the specularly reflected light in the image. In a preferred mode of practicing the invention, the color of specularly reflected light is detected by detecting a plurality of sets of points having constant hue and varying saturation on a plurality of differently colored surfaces in the scene, and determining the locus of the intersection of straight lines fit through the color values of the sets of points. The locus of the intersection of the straight lines indicates the color of the scene illuminant. In an application of the method in a color printer, the determined illuminant color is employed as the aim point in the photographic printing process.

Abstract: In a method for processing digital color images derived from photographic film, the method employing color reproduction functions generated by normalizing random samples of color values from different colors, oversampling of color values from color saturated textures such as green grass and blue sky noise can distort the randomness of sampling and result in unwanted color shifts in the processed digital images. The problem is solved by constraining the shapes of and relationships between the color reproduction functions in conformance with a priori knowledge of the photographic film, and photographic conditions. According to one aspect of the invention, the shapes of the color reproduction functions are constrained in conformance with the D-Log H curves of a color photographic film. According to another aspect of the invention, the relationships between the color reproduction functions are constrained in conformance with the assumption that the illuminant employed to expose the film was a black body radiator.