1. In apparatus for processing a digital color image value originally obtained from an image sensor or the like having color image pixels aligned in rows and columns having diagonal pixels with sufficient information to permit luminance estimation the digital image having at least three separate color values but only one color value for each image pixel location, such apparatus computing the luminance values for each image pixel, comprising: means for storing the digital image; processor means operative with said storing means and responsive to said stored measured digital color image values for computing low frequency luminance values; means responsive to the computed low frequency luminance values for obtaining Laplacian second-order and gradient values in at least two image orientations from neighboring image pixels; means for combining the Laplacian second-order and the gradient values to define a value for each image pixel in the kernel such that there are sets of values with each value corresponding to a classifier and for selecting a preferred orientation from a group of orientations for the interpolation based upon the classifier; and means responsive to the preferred orientation and the measured digital image for estimating a portion of the color specification for each corresponding image pixel.