Method for forming color images, using a hue-plus-gray color model and error diffusion

A color-halftoning method for actuating a color-generating machine to cause a visible medium to appear colored in correspondence with desired-color information from a source of such desired-color information;

• said method comprising the steps of:
• receiving from the source the desired-color information, and resolving the information into substantially hue, Fraction-Colorant and gray, if such desired-color information is not already so resolved;
• said hue, Fraction-Colorant and gray being expressed in terms of fractions of four active colorants, which are hereby defined for each pixel location of the machine as:
• dominant primary,
• subordinate primary,
• black, and
• white;
• then utilizing the information, while it is thus resolved substantially into hue, Fraction-Colorant and gray, to generate rendition-decision information substantially representing specific desired hue, Fraction-Colorant and gray at each pixel location of the machine;
• wherein the rendition-decision information comprises selecting for use at each pixel location a respective single colorant that can be implemented on the machine;
• then determining a dispersable error resulting from use of said single colorant instead of substantially said desired hue, Fraction-Colorant and gray;
• then dispersing said error substantially in terms of hue, Fraction-Colorant and gray to selected other pixel locations that are nearby;
• and
• after the information-utilizing step, applying information related to the single selected colorant to select and actuate one or more specific corresponding subsystems of the machine.

A color-halftoning method for actuating a color-generating machine that employs a plurality of colorants to cause a visible medium to appear colored in correspondence with desired-color information from a source of such desired-color information;

• said method comprising the steps of:
• receiving from the source the desired-color information;
• then utilizing the information to generate rendition-decision information representing a specific colorant at each pixel location of the machine, respectively, including the substeps of:
• expressing the desired-color information in terms usable for constraining the number of colorants employed by the machine, and
• constraining the generation of rendition-decision information to select only colorants having at least some specified degree of relationship to the input color expressed in said terms;
• and
• applying that generated rendition-decision information to:
• select specific subsystems of the machine for actuation in relation to specific pixel locations, respectively, and
• actuate those specific substances in relation to specific pixel locations.