First, trapping overview Wenzhou Vigorous Pet Products Co.,Ltd , https://www.vigorouspet.com
In the printing, due to the instability of the continuous paper, the relative position between the printing colors is caused to be skewed to the standard position; at the same time, when the paper is rotated at a high speed along with the drum, it will move horizontally or stretched; and the paper absorbs the dampening After the liquid and ink size will change, after the degree of deformation and so on. These factors will lead to overprinting. Uncertain colors create a small white border between adjacent pages, which is what people call luster. This white edge is very dazzling, affecting the appearance of the layout.
There are two methods to solve the registration problem:
1. Overprint or create an overlay bridge.
Overprinting is the overlaying of two color overlays. Thin lines and small text can use this method. The establishment of a set of color bridges refers to designing colors so that two overlapping blocks of color are intended to share a certain stencil color, and when the other stencil colors are overprinted, no bleed is revealed. If C20Y80 and Y60 overlap, there will be no whitening. This method brings great limitations to designers, and it is impossible to achieve special colors.
2. Doing trapping, also called make up white.
Trapping refers to the expansion or contraction of a color to make slight overlap between the two colors to compensate for misprints during printing. When the color of the object is averaged over the background color, the extension should be used to extend the edge of the object to the background color; otherwise, the contraction is applied, the background color is extended to the object, and the necessary stack is generated between the objects. The essence of expansion and contraction is the same, and the principle is to always extend the color with a small average density to a more dense color. This maintains the integrity of the shape as much as possible. Since the dew-whitening area is a transitional color and its width is very narrow, the human eye generally does not notice its existence, and thus produces a better visual effect.
Trapping is particularly important in map printing. Because there are numerous cross-overlapping elements in the map, each surface element is colored according to the classification of the ground features and the regional attributes, and the chance of exposure is greater. In addition, there are usually several spot colors in the map, and it is not possible to establish a layout color bridge, so traps can only be used to compensate for misprints.
Let's take a look at how digital trapping is specifically implemented in map publishing.
Second, digital trapping processing in map publishing
In the field of map publishing, there are mainly the following softwares currently used for map publishing in China:
1) Professional map publishing software. More used are the Mercator series from Barco, MapGis from China University of Geosciences, and Founder Zhimo.
2) Commercial electronic publishing software. In practice, graphics software and image processing software such as PhotoShop are often used in combination. The process flow: original image scanning - image processing - vectorization - vector editing and layout - color inkjet - output.
3) GIS software. Such as Arcinfo, Mapinfo, Geostar and so on. GIS and other software all use database technology to organize and manage geographic information for spatial analysis and network analysis. At the same time, geographic information is visualized by grouping graphics for years. The database of such software needs to spend a lot of manpower and material resources to establish and maintain, and there is no invincibility without printing. People publish maps for the purpose of starting using GIS software is neither appropriate nor cost-effective.
Therefore, at present, most of the domestic maps used for printing are the first two types of software. Let's discuss how commercial electronic publishing software and professional map publishing software implement trapping when publishing a map.
1. Trapping in professional map publishing software
Professional map publishing software is generally open to many formats of GIS data and PS files, and has good map editing and prepress processing functions. Barco's MercatorS/A series features powerful graphics editing capabilities, a good user interface, complete prepress processing technology, and print quality control features such as trapping, PS compliance checking, barcode addition, and print production control signs. . The Mercator series is used as an example to illustrate the implementation of trapping in professional map publishing software.
1) Parameter settings
In the Mercator Mapedge, pull down Trapping menu, the user can choose to automatically or manually trap the two ways. Click Options button, Traping Options panel appears, the user here to trap the various parameters of the fine settings.
(1) Scan
Before the system scans the file, the user here specifies the type of object to ignore during the scan, ie the object that is not intended to be trapped. At the same time to determine the maximum value of the ink, in order to avoid trapping where there is no need to trap. The principle of judgment is as follows:
If the two composite colors share a sufficiently high set color component and there are two or more component color differences of more than 20%, and the directions are the same, there is no need to make up for dew.
If the conditions of the two complex colors are the same as above but the color difference is in the opposite direction, it is necessary to make up for the dew.
For example, Table 1 shows.
Table 1
Process color ink color 1 color 2 color difference (1-2) processing result color 1 color 2 color difference (1-2) processing result
C 0 100 -100 Do not trap in the same direction 100 0 100 Do the trap in the opposite direction
M 40 70 -30 20 45 -25
Y 0 0 0 0 0 0
K 0 0 0 100 0 100
Max Gap Distance is used to set when the gap between two objects can be ignored for many hours, and when it is adjacent processing, it still needs to be trapped. Because in the normal mode, tiny gaps are not visible, but the actual printing will reveal the background color or paper color.
(2) trap type
There are four types of traps that can be generated in Mercator:
The usual trapping. That is, trapping is performed according to the usual expansion and contraction principle, resulting in a normal trapping edge. isolation. That is, a small white border is created where the trapped object overlaps or overlaps with the background object, so that the color of the two objects will not be confused and easy to identify.
Rich in black. That is, black information is overprinted with a black version and another color version to get darker black. This additional color version is usually set according to the color adjacent to or overlapping with black, and typically uses 69% cyan on a white background.
White background. When printing on metal or transparent materials, it is necessary to print a white background with white ink.
(to be continued)