A printing apparatus includes a head capable of discharging CMYK inks including a K ink, and a control unit configured to, based on image data to be printed, generate ink amount data for controlling an ink amount of each of the CMYK inks discharged by the head, and to control the head based on the ink amount data, wherein the control unit generates the ink amount data as ink amount data such that lightness of a composite color at least does not increase in a direction from a freely-selected coordinate point toward a black point, the composite color being formed by the CMY inks excluding the K ink based on ink amount data of each of the CMYK inks corresponding to a coordinate on a straight line from the freely-selected coordinate point toward the black point in a predetermined hue range of a color gamut of a color space of the image data.

An image forming apparatus includes a memory and a processor configured to output an image formed based on image data including predetermined specific text after replacing a color of one or more portions in the image data with a special color that is in advance associated with the specific text, the one or more portions being assigned a color identical or similar to a color of the specific text to form the image.

An example of a color management module is disclosed. The color management module is to generate a mapping from an incoming color space to a printer color space by a color pipeline. In the generation of the mapping, the color pipeline is adjusted so that the mapping of a target color associated with a first composition further includes adding a quantity of a second composition to the mapping of the target color. The second composition comprises a lower visibility than the first composition.

In a document represented by CMYK process colors, a color that a user wishes to remove is prevented from remaining without being removed by specified color removal, and even a color that the user does not wish to remove by rights is prevented from being removed.

An example system in accordance with an aspect of the present disclosure includes a halftone engine and a gray value engine. The halftone engine is to apply halftoning to an image recursively across a plurality of levels of image scales and spatial resolutions, to generate a pattern that is at least quasi-periodic across the plurality of levels. The gray value engine is to substitute gray values recursively for at least a portion of the halftoning.

A method for closed-loop color control in printing machines using a computer includes initially coating a printing substrate with opaque white to set up closed-loop color control in the course of a print job, subsequently applying process colors and, in the process, color measurement strips onto the opaque white, recording the opaque white and the color measurement strips using a measuring device, and, based on data recorded by the measuring device, performing closed-loop color control for process colors and opaque white using the computer. The measuring device is an inline measuring device and is initially calibrated at a fixed position of the printing substrate, then the application of opaque white is adjusted and, when a deviation stays below a maximum deviation, closed-loop control of both the opaque white and the process colors is done using the computer by taking measurements in the color control strip.

A method of color separation of a digital image into two color and black inks for four or more color printing, in which an original digital image is converted into coordinates of an opponent color space of a print according to base vectors of a paper and of the colored inks, and vectors of the relative application of said inks to the print. In the opponent color space, the color coordinates of base vectors of the paired application of two adjacent colored inks are determined on a CaS chromaticity diagram of the color characteristics of N colored printing inks. The colors that fall in the color gamut of the printing inks are separated into N sectors each group of colors of the image of the original is separated into two colored inks, which correspond on the CaS chromaticity diagram to a selected sector of the colors of paired application of these inks, and a third black ink, and N color-separation image channels for the colored inks and a single common separated image channel for the black ink are formed for all of the colors of the image of the original.

A printing method for performing printing while complementing black with composite black, the printing method including: printing a test pattern having a plurality of patch images for which composite mode varies, this test pattern being printed for each dot size of the black to be complemented; causing a user to select a desired patch image from among the plurality of the patch images included in the printed test pattern, the selection being made for each of the dot size of the black ink to be complemented; and performing printing while complementing the black to be complemented with the composite black generated on a basis of the composite mode corresponding to the desired patch image selected correspondingly to the dot size of the black ink to be complemented.

A method for detecting background color of a scanned document uses dynamic weights to adjust components of the L*a*b* color space. In accordance with one aspect of the disclosure, the L*a*b* values belonging to pixels within a block are applied to a series of thresholds. In response to the L*a*b* values meeting the thresholds, a given color pixel within the block is reclassified as being monochromatic. The weight values are dynamically updated based on at least one of the L*a*b* values of the given pixel. The thresholding is repeated for remaining pixels in the document. Using the classified pixels, an output document is generated where the background pixels are monochromatic. The output document is transmitted to a display device in communication with the server computer.

In an example, an apparatus is described that includes a plurality of fluid ejection devices, a database, and a raster image processor. The plurality of fluid ejection devices eject a plurality of fluids containing a plurality of different colorants. The database stores an entry for a spot color. The entry defines a first subset of the plurality of fluids that combines to emulate the spot color and a second subset of the plurality of fluids that combines to emulate the spot color. The second subset maximizes a number of the plurality of different colorants used. The raster image processor converts a page description of an image including the spot color into rasterized image data using the second subset of the plurality of fluids.