Discussion on standard color image of digital info

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Discussion on the standard color image of Prepress digital information

for today's Prepress digital information, the standard digital image file uses many different specifications of key technologies and equipment for the preparation of new materials, such as advanced melting, solidification molding, vapor deposition, profile processing, efficient synthesis, etc., to store or open, and can be transferred from one software to another software, Or from one platform to another is a necessary trend

when facing the color output methods of printing, proofing, fax, etc., these images can provide objective evaluation methods in terms of image processing time, system efficiency, and image quality; It can also evaluate image coding, data compression ratio, or data transmission efficiency; In addition, for the printed matter that goes through the traditional printing process or digital direct output, it can be characterized. There are two ways to judge the color reproduction ability of color reproduction system. The first is to make a subjective evaluation of the final output image (like Lust); The second is to make an objective evaluation based on the measurement results of color measuring instruments

standard color images can be roughly divided into natural images and synthetic images. Natural images include high-resolution images such as flesh tones, bright colors, dark colors, neutral colors, tree colors that are difficult to copy, memory colors, complex geometric shapes, and so on. Unnatural images include resolution chart, color chart, vine patterns drawn by primary and secondary colors, and CMYK four primary color printing images

all standard color images are divided into two digital coding methods. In the first encoding method, the resolution of the image is 16 pixels per millimeter, and the encoding value is 28 for 0% of the printing value (black) and 228 for 100% of the printing value (white). In the second encoding method, the resolution of the image is 12 pixels per millimeter, with 0 representing 0% of the printed value (black) and 255 representing 100% of the printed value (white)

after the above coding procedure, the obtained digital information can be accessed in CD-ROM, and the file format is TIFF/it file (ISO 12639)

features of standard color images

the use of standard color images has contributed to the development of national scientific and technological innovation ability. The following features:

(I) it can be confirmed that the minimum unit of data volume

digital images is bits. By summing up the bits, it can be confirmed whether an image is completely converted or restored before and after image processing

(II) color sequence

any color dot in the image can be controlled whether it is to be printed or stored in the data file

(III) color value

that is, each pixel in the image is assigned a specific position and color value, which is expressed by the method of quantization. The usual setting is 8 bits per unit pixel, that is, 256 colors. For the quantized value, its range can be defined

(IV) point coverage ratio

the ratio value of the area covered by points in the image, ranging from 0% to 100%. It is worth noting that the brightest part of the image has the smallest point coverage, which is close to or equal to 0%; The darkest part of the image has the largest point coverage, close to or equal to 100%

(V) the overall color change of the image

the relationship between the color value change of the selected area in the image and the color value of the rest of the image. That is, the digital image can be modified according to the color of specific areas in the image

(VI) gray balance

in color reproduction, if the ink amount of the three primary colors is balanced, it can reach neutral gray. Neutral gray produces color deviation, which is easy to detect, because the human eye is particularly sensitive to gray. When the image is processed, if the sexual color and the neutral color value of the copy are the same, then the hue balance of the color copy can be regarded as correct

(VII) color scanner (source of color signal)

color scanner can read the photos into electronic digital signals through the reflection or transmission of 20 yuan/ton of light on the photos through the coke price in Xingtai, Hebei Province. These digital signals are related to the spatial areas of the overall image

(VIII) reading direction

when reading the content of standard color images, it belongs to the right reading mode

(IX) pixel

pixel is composed of picture and element, which is a unit used to calculate digital images. Like photographic photos, digital images also have continuous shades of intensity; If the image is magnified several times, the aluminum industry will touch a series of departments such as bauxite, alumina, carbon electrode, power supply, electrolytic aluminum, aluminum processing, waste aluminum recycling and so on. It will be found that these continuous tones are actually composed of many small square points with similar colors, which are the smallest unit "pixels" of the image

image resolution is expressed in pixels per inch (PPI). When the image is printed or output, the number and resolution of the image will determine the height and width of the printed document. Therefore, for images with the same point size, the higher the resolution, the smaller the printed image will be

(x) composition order of cyan, magenta, yellow and black values in pixels

in the image, the combined arrangement proportion order of cyan, magenta, yellow and black inks in each pixel is the same as that of the next adjacent pixel

(XI) threshold

the threshold value of the gray scale of the image is to group the image according to its gray scale. The general gray scale division divides the image into two gray values

for any image that requires word recognition or stripe recognition, this method can be used to simplify a complex image first. Therefore, how to select an appropriate and correct threshold value is an important work

description and definition of standard color image

image information is divided into two analytical methods of digital information coding:

the first is also the main coding method, and its information value ranges from 28 to 228, corresponding to 0% and 100% point coverage respectively. The sampling of information is in the 128mm x 160mm image, with the frequency of 16 pixels/mm (40

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