Application of the hottest digital trapping techno

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Application of digital trapping technology in Map Publishing (Part 2)

(3) trapping shape

along the edge. When the specified trapping distance exceeds the contour line of the bottom object, the newly generated trapping edge will cut off the rest of me along the contour line of the bottom object

tilt. The trapping edge grows to the center line of adjacent objects at an oblique angle. If the distance to the center line exceeds the set trapping distance, the growth will stop

along the centerline. The first trapping edge does not grow along the edge. If the trapping edge is too close to the contour line of the bottom object, the growth will stop at the overall position of the center line. The complete trapping distance shall be applied at other places not close to it


build parameter specifies whether the growth direction of the trapping edge depends on the trapped object. Global distance defines the trapping distance. Corners specifies whether the corner of the trapped edge is a sharp corner or a rounded corner, and the chamfer ratio of the corner

(4) trapping color

users specify trapping color here. In recognition, the trapping color is usually the direct superposition of two colors, so the color is very dark, forming a prominent dark edge around the trapped object. Therefore, the trapping color usually needs to be properly reduced. For example, 70% of the mixed color is not easy to stimulate the vision

2) effect test

in production, the trapping level is divided into three levels, which are easy to difficult: (1) two simple pure color blocks overlap. (2) Multiple objects overlap each other; (3) Two gradient objects overlap. People often evaluate the trapping function of software by whether publishing software can correctly handle these three situations. General DTP software with trapping can mostly deal with the first two cases, but rarely with the third. Only a few software such as Photoshop and Mercator can do it. In Mercator, you can also trap the objects superimposed on the imported CT image. Moreover, the generated trap areas are placed in a separate layer as independent graphics, which is convenient for users to make more fine adjustments to the warp

2. trapping in commercial electronic publishing software

when using commercial electronic publishing software to publish maps, trapping can be realized in the following programs:

it is created in the special disclosure application software

it is created in the drawing program. For example, the built-in trap function can be used in Photoshop, illustrator of adobe company and Core1DRAW of Corel company for trapping

created in page collage programs such as ppagmaker and Xpress

although these software can trap, their processing methods, setting methods and application ranges are different

1) trapping of special exposure compensation software

special exposure compensation application software refers to the best option when encountering projects that are difficult to be exposed or when establishing a wide and accurate exposure compensation value for a printing machine. It converts image information into pixels and points, and then automatically generates traps on all adjacent objects. It can generate adjacent gradients and input EPS pictures. 3. The measurement of beam displacement is roughly the same as that of deformation measurement. The user can also control the details. But this software is expensive, and the processing process is long and time-consuming

2) trapping in PS

photoshop can trap adjacent colors in the whole image when the image mode is CMYK. The user only needs to input the trapping width. When processing, the computer first judges the depth of the foreground and background color, and then automatically performs expansion or contraction processing. The trapping color is the mixed color of the foreground and background. Because this is a pixel based trapping, trapping edges can also be generated for imported EPS images and gradient objects. The color is a mixed color at the border, but the trapping direction is uncertain and the edge is fuzzy. The generated right angle trapping edge breaks at the corner

3) trapping in Core1DRAW and PageMaker

core1draw is a vector software used most by some small map publishing houses in China at present, and it is one of the most powerful software in non professional map publishing software

core1draw and PageMaker provide an automatic trapping function for text and graphics of the entire layout. It cannot set trapping values for specific objects. Under Core1DRAW trapping setting, before output, the user can choose whether to trap, overprint all colors in rip or use automatic extended trap in file/print.../color separation. If you choose to automatically expand trapping in Core1DRAW, you need to determine the trap width and the threshold number of text points to trap the text. In the supplementary exposure option panel of PageMaker, you can set the supplementary exposure width, color step threshold, center line threshold, number of text points and black version limit respectively. Among them, the step length refers to how much contrast between colors is needed to make up the white; The midline threshold value refers to how much the neutral density of two colors reaches, and the trapping will extend to both sides along the middle line of two colors. Neither Core1DRAW nor PageMaker can add white to gradient objects and imported images

With the development of computer technology, digital trapping technology has become a powerful and indispensable means to achieve high-quality printing. The digital trapping technology plays a particularly important role in the map printing where the layout reproduction UTM can also be used for product quality control, the spot color is used more, and manual trapping is almost impossible. However, trapping is a very complicated work. The determination of trapping value and the adjustment of trapping color often need the guidance of professional printers. Therefore, more attention should be paid to the following points during digital trapping:

1. trapping should be avoided when designing regional color; Do not use compound colors for small words and thin lines. It is better to use embossing

2. trapping is not required in all places where adjacent colors appear. It shall be judged in advance according to the following principles:

when there is small black information overprint, trapping is not required; However, trapping is required for large-area black excavation

no trapping is required for the graphics with thick black outline

in four-color printing, if the adjacent colors are monochrome, the composite material needs to contain 9% graphene trapping; Trapping is also required if both are composite colors and do not share any overprint color components. For example, color 1 is c100k50 and color 2 is M100. Since they do not share any overprint color components, trapping is required

in multi-color printing, the spot color is adjacent to other colors, and trapping must be done

3. the trapping width should be adjusted according to different objects to ensure the integrity of the graphic outline

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