Abstract: A method of JPEG compression of an image frame divided up into a plurality of non-overlapping, tiled 8×8 pixel blocks Xi. A global quantization matrix Q is determined by either selecting a standard JPEG quantization table or selecting a quantization table such that the magnitude of each quantization matrix coefficient, Q[m,n] is inversely proportional to the aggregate visual importance in the image of the corresponding DCT basis vector. Next a linear scaling factor Si is selected for each block, bounded by user selected values Smin and Smax. Transform coefficients, Yi, obtained from a digital cosine transform of Xi, are quantized with global table Smin Q while emulated the effects of quantization with local table Si Q and the quantized coefficients Ti[m,n] and global quantization table Smin Q are entropy encoded , where Smin is a user selected minimum scaling factor, to create a JPEG Part 1 image file.

Abstract: A system and method for determining a natural color depth of a digital image is described. Color distances between each pair of colors in a color palette stored for a digital color image are determined. A closest neighboring color for each color in the color palette separated by a substantially minimum color distance is selected. Each color pair that is visually indistinct is merged in iterative sequence.

Abstract: A method of JPEG compression of an image frame divided up into a plurality of non-overlapping, tiled 8×8 pixel blocks Bij where i, j are integers covering all of the blocks in the image frame. A global quantization matrix Q is determined by either selecting a standard JPEG quantization table or selecting a quantization table such that the magnitude of each quantization matrix coefficient, Qij is inversely proportional to a visual importance, Iij, to the image of a corresponding DCT basis vector. Next a linear scaling factor Sij is selected which defines bounds over which the image is to be variably quantized. Transform coefficients, Dijmn, obtained from a digital cosine transform of Bij, are quantized and the quantized coefficients Tijmn and Q*Smin are entropy encoded, where Smin is a user selected minimum scaling factor, to create a JPEG image file. The algorithm is unique in that it allows for the effect of variable-quantization to be achieved while still producing a fully compliant JPEG file.