The experimental process flow using multiply congruent pseudo-random screening is shown in Figure 2. Raster image processor (abbreviated as RIP) is the core of the color desktop publishing system. Its main role is to interpret the image, graphics and text information in the page file described by the page description language, convert it into dot matrix information, and control the printer or The imagesetter records dot matrix information on paper or film. RIP is divided into hardware RIP and software RIP, generally for amplitude modulation screening. The original image is scanned and collected by the scanner, and then processed by image processing software (photoshop) for color correction, gradation adjustment, color separation, etc., and then the frequency modulation screening is carried out by the multiply congruence pseudo-random method. The screened image is assembled into the required layout by grouping software (PageMaker), and then sent to RIP after proper processing to control the output of the imagesetter, and the purpose of borrowing the existing RIP to complete the frequency modulation and screening can be achieved. The results of the study confirm that this is feasible, which opens the way for frequency modulation and screening using the hardware and software of the existing DTP system. The research uses novaRIP (a software RIP), which has the advantage that it can predict the results of the screening and find that the problem can be revised repeatedly. For simplicity, first try to randomly screen the grayscale image. Figure 3 is a sample image output on a laser printer with an output resolution of 600dpi. In color printing, large areas of spot color with the same tone and level are difficult to replicate. We tried this in the Air Force Xi'an Printing Factory, and achieved satisfactory experimental results. When randomly screening, the texture will appear when the gray value is high. We think that the main reason for this phenomenon is that when there are a large number of pixels with the same gray value in the image, due to the use of the same pseudo-random number sequence distribution, the distribution rules among each other are the same, thereby forming a texture, as shown in Figure 4a Show. In this regard, as long as measures are taken, when pixels of the same gray value are screened, different sequence starting points are used in the same random number sequence, or different random number sequences are used to make their distribution rules different from each other, thereby avoiding texture The phenomenon occurs, as shown in Figure 4b. Two Seater Sofa Beds,Sleeper Bed Sofa,Pull Out Queen Sofa Bed Foshan Shunde Baotian Furniture Co., Ltd. , https://www.baotian.com
Figure 2 Process flow chart of multiply congruence pseudo-random screening experiment Click here to view all news pictures
Figure 3 The output result of the random screen of the gray image Click here to view all news pictures
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