Patent ID: 7573621

Claim:
A method of transforming a pixel defined by received C, M, Y color values having a sum that is not less than a maximum allowed paper coverage max_cov that is set to a greater of (1) a preset ink limit preset_cov and (2) the maximum of the C,M, Y color values, into K, Cout, Mout, Yout, and S-Color values, comprising: receiving values C, M, and Y from a host computer; storing print data C, M, and Y in a computer buffer memory; assigning a maximum of the C, M, Y values to max_color; assigning a middle of the C, M, Y values to mid_color; assigning a minimum of the C, M, Y values to min_color; selecting a black color value K that is not greater than a minimum of min_color and (C+M+Y−max_cov)/2; obtaining a max_color_out value by calculating (T−mid_color), wherein T=max_cov−min_color+K; obtaining a mid_color_out value by calculating (T−max_color); obtaining a min_color_out value by calculating (min_color−K); obtaining a secondary color value S_color by calculating (max_color+mid_color−K−T); assigning through use of a computer processor, each of max_color_out, mid_color_out and min_color_out to one of Cout, Mout or Yout depending on the relative magnitudes of the C, M, Y color values such that: if C>M>Y, then Cout=max_color_out, Mout=mid_color_out and Yout=min_color-out; if M>Y>C, then Cout=min_color_out, Mout=max_color_out, and Yout=mid_color_out; if Y>C>M, then Cout=mid_color_out, Mout=min_color_out, and Yout=max_color-out; and half-toning K, Cout, Mout, Yout, and S_color, in order to transform continuous tone data into half toned bit map that contains one bit per pixel per primary color.