Patent ID: 8072648
Filing Date: 2011-12-06
Classification: G06K,H04N

Abstract:
1. A method for compensating for spatial non-uniformities in a printer, said method comprising: generating a true average tone response curve for a color channel, wherein the true average tone response curve defines an average true response for the printer across a printed output spatial range; generating a predicted average tone response curve for the color channel, wherein the predicted average tone response curve defines an average predicted response for the printer across the spatial range; generating a predicted true tone response curve for the color channel, wherein the predicted true tone response curve defines an predicted actual response for the printer for each print location in the spatial range; generating an estimated true tone response curve for the color channel using the true average tone response curve, the predicted average tone response curve, and the predicted true tone response curve, wherein the estimated true tone response curve defines an estimated actual response for the printer as a function of each print location in the spatial range and as a function of each possible digital input color level to the printer, wherein said estimated true tone response curve is represented by TRC where x represents said spatial location, i represents a color channel, H represents a halftone screen; using said estimated true tone response curve to correct a digital color level of each pixel of an image for the color channel before printing based upon said print location of each pixel of said image and based upon said digital color level of the pixel; wherein said step of generating a predicted true tone response curve for the color channel comprises: using the printer to print a plurality of different 2×2 test patches at each location in the spatial range using said color channel and measuring a 2×2 color value of each 2×2 test patch at each location in the spatial range to obtain a measured 2×2 color value for each test patch at each location in the spatial range; deriving a plurality of binary halftone patterns for a corresponding plurality of online digital input color values; deriving a model for each of said plurality of binary halftone patterns, wherein said model is such that each of said binary halftone patterns is represented by a respective group of said 2×2 test patches; for each location in the spatial range, using the measured 2×2 color values, at said location, of the 2×2 test patches included in the model to predict a color output value for each of said binary halftone patterns, wherein each predicted color output value is related to one of said plurality of online digital input color values to thereby define said predicted true tone response curve for the color channel.