1. A method for compensating for spatial non-uniformities in a printer, said method comprising: pre-identifying a plurality of halftones for which said compensation is to be supported; pre-generating a true average tone response for each of the plurality of halftones and for each color channel, wherein the true average tone response curve defines an average across a range of spatial locations on the printed page; receiving a specific halftone from said plurality of supported halftones; printing and measuring a set of halftone-independent binary color patterns; deriving an estimated true tone response curve for said halftone and for a given color channel using pre-generated true average tone response for said halftone, and measurements of halftone-independent color patterns; wherein said step of re-generating a true average tone response for each of the plurality of halftones and for each color channel comprises an offline step of generating a true average tone response curve for a color channel and halftone, wherein the true average tone response curve defines an average true response for the printer across a printed output spatial range; wherein said step of deriving an estimated true tone response curve for said halftone and for a given color channel comprises the online steps of: generating a predicted tone response curve for the color channel, wherein the predicted tone response curve defines a predicted actual response for the printer for each print location in the spatial range; generating an averaged predicted tone response curve for the color channel from the just obtained predicted tone response curve, wherein the averaging is performed for each tone or gray level over the spatial range of the printer; generating the estimated true tone response curve for the color channel using the true average tone response curve, the predicted tone response curve, and the redicted averaged 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, said estimated true tone response curve represented by TRC true (x,i,H), said true average tone response curve represented by TRC true avg (i, H), said predicted average tone response curve represented by TRC 2×2 avg (i, H), and said predicted true tone response curve represented by TRC 2×2 (x,i,H), wherein said estimated true tone response curve is determined according to the following equation: TRC true ⁡ ( x , i , H ) = TRC true avg ⁡ ( i , H ) ⁢ TRC 2 × 2 ⁡ ( x , i , H ) TRC 2 × 2 avg ⁡ ( i , H ) where x represents said spatial location, i represents a color channel, H represents a halftone screen; said method further comprising 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.