Detailed Prepress Operation - Separation Work Chapter Ten (I)

X. Special effect color separation

1. Production of skeleton version and line version (production of binary images)

When making a stencil, first of all, we must carefully analyze the content of the original decision, then set the scan line number of the extension to ≥250L/inch, and transfer it to the binarization function. Then select the image in the image. The white and black cutoff values ​​are shown in Figure 6.25. If 50% of the dots in the image are the demarcation points, <50% of the output value is 0 and ≥50% of the output value is 100%. As long as the image analysis is correct, the desired stencil version can be obtained by selecting the appropriate demarcation point.

The production method of the line version is similar to the production of the stencil version, that is, the preset number of screen lines is ≥250L/inch. During the calibration, the settings of the highlight or dark point of the line version are the same as those of the conventional separation scanning. The control parameters of the black and white scanning are used, and then the binary function is entered, and then the demarcation point is selected. The demarcation point selection should ensure the integrity of the line drawing. The principle of smooth lines and cleanliness.

2. Deformation processing

Deformation processing is also called vertical and horizontal magnification change. In color image copying, outputting an image with different magnification ratios for some originals can change the visual composition of the image, enhance the image of the printed product itself, and can also satisfy special effects. For example, in a sample of a car, if it is highly compressed, it can give a high-level image and increase the user's desire to buy. Therefore, consciously use the magnification change function and cooperate with the designer to get the taste that the original design can not achieve. As shown in Figure 6.26, when the design is, for example, there is a lack of blue spots or a partial sky must be repeated, you can set different aspect ratios. Make the required sky.

When the aspect ratio is set, the visual influence of the image distortion caused by the different proportional relationship between the two should be fully considered. Special requirements can also change the position of the original on the scanning drum and the tilt angle to achieve the intended purpose.

(to be continued)