Hue compensation apparatus for a color hard copy machine

A method of hue-compensating for outputting hue-compensated data of a color designated by an input color signal of one of red, green and blue, responsive to red, green and blue input signals, comprising the steps of:

• outputting only a single hue-compensated red signal in response to an input red signal via a first lookup table means;
• outputting only a single hue-compensated green signal in response to an input green signal via a second lookup table means;
• outputting only a single hue-compensated blue signal in response to an input blue signal via a third lookup table means;
• decoding an input color selection signal and outputting a decoder signal responsive thereto;
• polarizing outputs from said hue-compensated red, green and blue signals according to said decoder signals;
• and
• synthesizing said polarized outputs,
• wherein said hue-compensated red, green and blue signals are inputs to a plurality of polarizing circuits in said polarizing step and said decoder signals are input as a second input to each of said plurality of polarizing circuits in said polarizing step.

A hue compensation apparatus, comprising:

• a first look-up table having a first input terminal receiving a red color signal, a second input terminal receiving a color selection signal, and an output terminal for outputting a hue-compensated red signal;
• a second look-up table having a first input terminal receiving a green color signal, a second input terminal receiving said color selection signal, and an output terminal for outputting a hue-compensated green signal;
• a third look-up table having a first input terminal receiving a blue color signal, a second input terminal receiving said color selection signal, and an output terminal for outputting a hue-compensated blue signal;
• a first polarity circuit for polarizing the hue-compensated red signal and having a first input terminal connected to said output terminal of said first look-up table to receive the hue-compensated red signal, a second input terminal, and an output terminal;
• a second polarity circuit for polarizing the hue-compensated green signal and having a first input terminal connected to said output terminal of said second look-up table to receive the hue-compensated green signal, a second input terminal, and an output terminal;
• a third polarity circuit for polarizing the hue-compensated blue signal and having a first input terminal connected to said output terminal of said third look-up table to receive the hue-compensated blue signal, a second input terminal, and an output terminal;
• a decoder circuit having an input terminal receiving the color selection signal and first, second and third output terminals respectively connected to the second input terminals of said first, second and third polarity circuits, said decoder circuit outputting control signals at said first, second, and third output terminals for controlling said polarity circuits to polarize the hue-compensated signals in accordance with the color selection signal;
• and
• an adding circuit having input terminals respectively connected to the output terminals of said polarity circuits for adding the output signals of said polarity circuits to provide non-linearly hue-compensated signals.

A hue compensation apparatus, which outputs hue-compensated data of a color designated by an input color selection signal of red, green and blue, responsive to red, green and blue input signals, comprising:

• first lookup table means for outputting only a single hue-compensated red output signal in response to an input red signal;
• second lookup table means for outputting only a single hue-compensated green output signal in response to an input green signal;
• third lookup table means for outputting only a single hue-compensated blue output signal in response to an input blue signal;
• decoder means for decoding an input color selection signal, and for outputting an output signal responsive to said decoded input color selection signal;
• polarizing means for polarizing said hue-compensated output signals from said first, second, and third lookup table means according to said output of said decoder means;
• and
• synthesizing means for synthesizing said polarized output signals from said first, second and third lookup table means,
• wherein said input color selection signal is a separate signal from said red, green and blue input signals;
• said polarizing means designates that said synthesizing means perform one of addition and subtraction of said output signals from said first, second and third lookup table means;
• said output signals from said first, second and third lookup table means are passed through said polarizing means to said synthesizing means;
• each of said output signals from said first, second and third lookup table means is n bits,
• and wherein said polarizing means comprises a switch for designating a polarity of addition as an (n+1)th bit from said n bit output signal from one of said lookup table means, and for outputting as an (n+1)th bit a value of an nth bit from said n bit output signals from said remaining lookup table means, respectively.

A method of hue-compensating for outputting hue-compensated data of a color designated by an input color signal of one of red, green and blue, responsive to red, green and blue input signals, comprising the steps of:

• outputting only a single hue-compensated red signal in response to an input red signal via a first lookup table means;
• outputting only a single hue-compensated green signal in response to an input green signal via a second lookup table means;
• outputting only a single hue-compensated blue signal in response to an input blue signal via a third lookup table means;
• decoding an input color selection signal and outputting a decoder signal responsive thereto;
• polarizing outputs from said hue-compensated red, green and blue signals according to said decoder signal;
• and
• synthesizing said polarized outputs, wherein said input color selection signal is a separate signal from said input color signal, and
• wherein the step of polarizing includes outputting a polarity of addition as an upper additional bit to said hue-compensated output of said color designated by said color selection signal, and outputting values identical to most significant bits from remaining hue-compensated signals as upper additional bits to those signals, respectively.