Printing image information processing - continuous tone modulation tone (3)

4. The dot shape refers to the shape of a 50% dot. Commonly used dot shapes are square, round, oval, chain, and so on. In addition, in the printing and copying, in order to achieve a special artistic effect, some special shapes of dots, as shown in Figure 3-6.

Figure 3-6 Special outlets

(b) Since the 1990s, the FM network has produced FM-screening methods for images, and there have been FM network outlets, also called FM network outlets. It is the use of computers, formed with the cooperation of hardware and software. The distribution of outlets in space is irregular and randomly distributed. The area of ​​each outlet remains the same. It depends on changing the density of outlets, that is, changing the frequency of the distribution of outlets in the space, giving all-rounders the ability to reproduce the light and dark levels of the images on the printed matter. See Figure 3-7.

Figure 3-7 Reproduction of tone points in FM mesh

FM outlets and AM outlets are all area modulated outlets. However, due to the existence of angle problems, the AM outlets often appear to be detrimental to the beauty of the printed image, due to improper angles or other reasons, as shown in Figure 3-8 (a). The FM network is random, there is no angle problem, it will not produce turtle, as shown in Figure 3-8 (b) below. In addition, the resolution of the FM network is higher than that of the AM network. Therefore, the reduction of the image tone exceeds that of the AM network.

Figure 3-8 The turtle site of the AM network