Features of digital image processing for multicolor printing

A search and analysis of recent researches on printing is carried out with expanded color gamut which includes six- and seven-color printing in cyan, magenta, yellow, black and additional colors: orange (red), green, violet (blue). Expanded Gamut Prin­ting requires a new approach to color management software. To ensure accurate color reproduction of printing products, such companies as: GMG Color, Alwan Color Exper­tise, CGS Oris, ColorLogic, Heidelberg, Kodak are represented on the market of software products and innovative solutions. The process of color separation of the image into additional colors in the plugin for Adobe PhotoShop Touch 7 Photo ECG by ColorLogic is described. A comparison of the color coordinates of the additional colors orange (O), green (G) and violet (V) used by the Touch 7 Photo ECG plugin and the Fogra55 ICC-profile is made. The common one is a violet ink corresponding to Pantone Violet C from the Pantone+ Solid Coated library. The areas in the image that will not be reproduced colorimetrically accurately by CMYK inks are highlighted. It is visually noticeable that additional colors are applied to areas of the image that will not be colorimetrically accurately reproduced by the specified printing conditions. With the help of the developed computer program, it is determined that 47.8% of the image pixels have non-reproducible colors under the given printing conditions. During color separation in the studied software module, additional colors occupy 88.2% of the image, which indicates that not only pixels whose colors are outside the gamut will be reproduced with additional colors. Additional colors according to the Fogra55 exchangeable color space synthesize colors that are close in color tone. The advantage of using the Touch 7 Photo ECG plugin is its multifunctionality. It presents various options for combining additional colors, as well as the option to choose only one of them. Therefore, the use of an ICC-profile or plugin will depend on the color characteristics of the original image and the printing requirements.

Keywords: multicolor printing, color gamut, ICC-profile, additional inks, Expanded Color Gamut, color separation, plugin.

doi: 10.32403/0554-4866-2022-2-84-44-53