Certain examples described herein relate to a method of electro-photographic printing. In an example a calibration image having one or more gray levels is printed using an optical element. The contrast of the printed calibration image is increased when the calibration image has a gray coverage below a threshold. The printed calibration image is scanned to determine adjustment factors for the optical element for the one or more gray levels. The adjustment factors are applied to the optical element when printing a non-calibration image.

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 and machine for digital printing with neutral colors, wherein the method uses a digital printing machine which has a print head which in turn has an ejector; providing a substrate for receiving digital printing; providing a printing product which has at least one light black (LK) printing ink having a concentration of black pigment that is lower than that of a black (K) ink; arranging the ejector with the printing product such that it is arranged for ejecting the printing product on the substrate; and performing digital printing on the substrate by means of ejecting the printing product according to a predefined design having at least one neutral color.

A method, system, and apparatus for rendering a security mark on a recording medium can involve creating a metameric pair of fluorescent inks with a first fluorescent ink among the metameric pair of fluorescent inks that blocks UV light and a second fluorescent ink among the metameric pair of fluorescent inks that does not block UV light, configuring at least one fluorescent ink among the metameric pair of fluorescent inks with a first pattern based on a constant pixel high surface and at least one other fluorescent ink among the metameric pair of fluorescent inks with a second pattern based on a substantial amount of white space, and defining a security mark for rendering on a recording medium with the metameric pair of fluorescent inks and based on the first pattern and the second pattern.

An example method comprises identifying a plurality of supply levels corresponding to a plurality of print supplies of a print device, and adjusting a color for a region of a print job for the print device based on the plurality of supply levels. The method further comprises initiating execution of the print job using the adjusted color for the region.

In a predetermined look-up table, in which each of a plurality of grid points that are defined by dividing each axis of RGB color coordinates is associated with a combination of density values respectively corresponding to a plurality of inks to be used by a printing apparatus, the plurality of grid points include a first grid point, at which a density value of a predetermined ink among the plurality of inks dose not correspond to 0, and a second grid point, at which the density value of the predetermined ink corresponds to 0, and the first grid point does not exist at points adjacent to each other in the plurality of grid points.

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 information processing apparatus includes a processor configured to, in accordance with a proportion of a black component with which to replace one or more non-black components that are color components other than the black component, replace the one or more non-black components with the black component for an image. The proportion of the black component is determined by brightness of the image, and when saturation of the image varies in a saturation range, the proportion decreases to a minimum value of the proportion with increasing saturation of the image and increases with increasing saturation of the image after the proportion decreases to the minimum value of the proportion.

An image processing apparatus includes: an acquisition unit configured to acquire a plurality of first color values in a device independent color space, from information defining a predetermined gamut; a setting unit configured to set predetermined first dot percentages of a fluorescent color for the plurality of first color values acquired by the acquisition unit; a calculation unit configured to calculate a second dot percentage of the fluorescent color, based on a relationship between the plurality of first color values and the first dot percentages, the second dot percentage corresponding to an arbitrary second color value in the color space; and a generation unit configured to generate a first profile to convert the second color value to dot percentages of a process color and the fluorescent color, based on the second color value and the second dot percentage calculated by the calculation unit.

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.