Brief analysis of the basics of hanging network

The separated images are four grayscale images with continuous tones. In four-color printing, only one ink can be used for each printing, and the ink concentration remains unchanged. In order to obtain a continuous tone at the time of printing, it is necessary to perform a netting process on the grayscale image. Hanging nets, also known as screening, is the process of breaking down continuous-tone images into dots.

After adding the screen, the size and density of the dots reflect the depth of the actual color of the image. Based on human visual effects, when viewing an image from a close distance, the dots and their surrounding space create continuous tone artifacts. Larger dots look darker, smaller dots look brighter, dots densely look like Dark, sparsely populated areas look bright.

There are many ways to hang the net. According to the different positions of the graphics, the nets can be divided into front-end hanging nets and back-end hanging nets; according to the method of forming net points, they can be divided into amplitude modulation (AM) and frequency modulation (FM). method. The front-end hanging net is also called software hanging net. It is to do the netting processing before the image is output in the layout, and then the image data after the netting processing is stored on the disk for the printing output.

The characteristics of this method of hanging nets are: slow processing speed, occupying a large amount of disk space, but strong flexibility, easy to upgrade and change.

The back-end hanging net is also called hardware hanging net, which is a method for high-speed netting of images by the RIP of the grid processor while the images are being output.

The characteristics of this method are: fast processing, saving disk space, but it needs RIP support, is not easy to upgrade, and has poor flexibility. AM webbing is a half-tone method of printing by changing the size of the printing dots during printing. The dots are dark in the large dots and bright in the dots.

In this method, moire is generated due to the interference of the grid pattern. This is a traditional hanging net technology. FM hooking is to print the dots of the same size in a random pattern, and the halftone method is implemented by changing the sparseness of the dots. The dark spots in many locations are dark and the places with few spots are bright. With this method, there are no rules for the placement of dots, and the print will not form a certain line and no interference pattern will be produced.