In an example implementation, a method of rosette-free printing includes, in a printing device whose color plane misregistration is less than 15 percent of a screen ruling of a halftone screen, printing multiple color planes of a multicolor image using the halftone screen.

An image processing apparatus capable of improving image quality of binarized image data is provided. The image processing apparatus includes a generation part that generates a binarized image data. The binarized image data comprises a first cell, containing a first dot pattern in which an outside pixel density is higher than an inside pixel density; and a second cell, containing a second dot pattern in which an inside pixel density is higher than an outside pixel density.

An image processing apparatus includes processing circuitry. The processing circuitry is to acquire image data including primary color image data for primary color and spot color image data for spot color; generate primary color halftone data representing the primary color image data as a group of halftone dots, using a primary color screen specifying cyclic arrangement of lines of halftone dots; and generate spot color halftone data representing the spot color image data as a group of halftone dots, using a spot color screen having a second phase that is different from a first phase represented by the cyclic arrangement of lines specified in the primary color screen.

In some examples, a printing device component includes a memory device comprising compressed coefficients that, when decompressed by a printing device, form difference entries, wherein a difference entry of the difference entries represents a difference of a value of a corresponding entry of a halftone table and a value of a corresponding entry of a reference table. The memory device further includes healing parameter values specifying a healing process to apply to a reconstructed halftone table produced using the coefficients.

Example implementations relate to halftone image creation. An example non-transitory machine-readable medium can include instructions executable to determine a highlight core shape and a shadow core shape of a microcell within a supercell. The instructions can be executable to determine growth sequences for a plurality of pixels within the highlight core and the shadow core and between the microcell and other microcells within the supercell, divide each of the plurality of pixels into a plurality of subpixels, and create a halftone image for an unequal resolution printing device using a constrained direct binary search model and based on the highlight core shape, shadow core shape, growth sequences, and the plurality of subpixels.

Example implementations relate to halftone image creation. An example non-transitory machine-readable medium can include instructions executable to determine a highlight core shape and a shadow core shape of a microcell within a supercell. The instructions can be executable to determine growth sequences for a plurality of pixels within the highlight core and the shadow core and between the microcell and other microcells within the supercell, divide each of the plurality of pixels into a plurality of subpixels, and create a halftone image for an unequal resolution printing device using a constrained direct binary search model and based on the highlight core shape, shadow core shape, growth sequences, and the plurality of subpixels.

A method comprises forming a halftone screen set comprising first, second and third halftone screens. A first regular halftone screen for the screen set is selected. A second regular halftone screen is determined, using a processor, by performing a regularity invariant transformation on the first regular halftone screen. A third halftone screen is determined based on at least one predetermined condition being satisfied between the first, second and third halftone screens.

In an example, a halftone screen is generated. A plurality of amplitude-modulated dot clusters is arranged in correspondence with a grid. Each of the amplitude-modulated dot clusters comprises a plurality of frequency-modulated dots.

Threshold values in a dither matrix are arranged such that, in a case when screen processing is executed on a multi-tone image that has a first density, halftone dots are formed at a first screen angle, and, in a case when screen processing is executed on a multi-tone image that has a density being higher than a second density that is higher than the first density, halftone dots are formed at a second screen angle that is different from the first screen angle.

A metallic image forming method is a method for forming a metallic image with a metallic ink containing an organic coloring agent capable of exhibiting a metallic color on a recording medium provided with an undercoat layer thereon having a black color or an opposite color to the color of diffused light from the metallic ink. The method includes applying the metallic ink onto the recording medium so as to cover at least part of the undercoat layer.