Discussion on standard color images of E - Corrugated Display Boxes with prepress information

Discussion on standard color images of E - Corrugated Display Boxes with prepress information

 

It is a necessary trend for today's prepress digital information to store or open standard digital image files in many different specifications and to be transferred from one software to another or from one platform to another.

 

These images in the face of printing, proofing, fax and other color output, can be in the image processing time, system efficiency, and image quality, to provide an objective way of evaluation; The image can also be encoded, data compression ratio, or data transmission efficiency evaluation; In addition, printed materials exported directly by traditional printing process or by digital characterization could be characterized. There are two ways to judge the color reproduction ability of color reproduction system. One is to do subjective evaluation of the final output image (color preference); The second is to measure the results of the color instrument to do objective evaluation.

 

Standard color image can be roughly divided into naturalimage (naturalimage) and unnatural image (syntheticimage) two types. Natural images include fleshtones, brilliant light colors, dark colors, neutralcolors, difficult-to-reproduce tree colors, memorycolors, complex geometric figures, and other high resolution images. The non-natural images include resolutionchart, colorchart, vine pattern drawn by primary and secondary colors, and CMYK four primary color printing images.

 

All standard color images are divided into two digital encoding modes. In the first encoding mode, the image resolution is 16 pixels per millimeter. the encoding value is 28 representing 0% of the print value (black) and 228 representing 100% of the print value (white). In the second encoding mode, the image resolution is 12 pixels per millimeter. the encoding value is 0 representing 0% of the printing value (black) and 255 representing 100% of the printing value (white).

 

The resulting digital information can then be stored in a CD-ROM file in TIFF/IT format (ISO12639). [next]

 

Standard color image features

For using standard color images, there are several features:

 

(I) The amount of data that can be confirmed

The minimum unit of digital image is bit. By adding up the bits, it can be confirmed whether an image is completely converted or restored before and after image processing.

 

(2) Color sequence

Any color point in the image, whether it is to be printed or stored in a data file, can be controlled.

 

(3) color value

That is, each pixel in the image has specified a specific position and color value, which is expressed by the Numeric method. The usual setting is 8 bits per unit pixel, i.e. 256 colors. For quantized values, you can define their range.

 

(4) network coverage ratio

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

 

(5) The overall color change of the image

The relationship between the color values of the selected area in the image and the color values of the rest of the image. That is, the digital image can be modified for specific areas of the image color.

 

(6) grey balance

In color reproduction, if the amount of the three primary colors overlapping ink to achieve balance, it can achieve neutral gray. Neutral grays create a bias that is easy to detect because the human eye is particularly sensitive to grays. When the image is processed, if the sexual color and the neutral color value of the copy are the same, then the color balance of the color copy can be considered correct.

 

(7) Color scanning machine (color signal source)

A colour scanner can read a photograph into an electronic digital signal, which is relevant to the spatialareas of the overall image, through the reflection or transmission of light on the photograph.

 

(8) Reading direction

When reading the content of the standard color image, it belongs to the right-reading mode.

 

(9) Pixels

Pixel, composed of the letters Picture and Element, is a unit used to calculate digital images. Like photographic photographs, digital images have continuous shades and shades; If the image is magnified several times, it is found that these continuous tones are actually made up of a number of similar square dots, which are the smallest units of the image called pixels.

 

Image resolution is expressed in pixelsperinch (ppi). When an image is printed or output, the number and resolution of the image determines the height and width of the image that appears on the printed document. Therefore, the higher the resolution of an image of the same number of dots, the smaller the image will be printed.

 

(10) The composition sequence of the four color values of blue, magenta, yellow and black in pixels

In the image, the blue, magenta, yellow and black inks of each pixel are arranged in the same proportional order as the next adjacent pixel.

 

(11) threshold value (threshold)

The threshold of gray level of image is to group the image according to its gray level. The general gray level will divide the image into two kinds of gray level.

 

This method can be used to simplify a complex image that requires text recognition or stripe recognition. Therefore, it is an important task to select appropriate thresholding values. [next]

 

Description and definition of standard color images

Image information can be divided into two kinds of digital information encoding parsing methods:

The first, and main, encoding method has information values ranging from 28 to 228, corresponding to 0% and 100% dot coverage, respectively. Information sampling is performed in a 128mmX160mm image with a frequency of 16pixels/mm (406pixels/in).

 

The second and secondary encoding method has information values ranging from 0 to 255, corresponding to 0% and 100% dot coverage, respectively. Information sampling is performed in 128mmX160mm image with a frequency of 12pixels/mm (305pixels/in).

 

Through the above two standard color image coding methods, the digitized images produced by the computer have both natural image (phto-graphed) and unnatural image (synthetic).

 

ISO12640 uses the first image encoding method to produce eight natural images, the code is N1~N8; For natural images produced by the second image coding method, "A letter "is added to the code from N1 to N8, namely N1A to N8A.

 

The unnatural image contains resolution test charts and color tickets. The non-natural images produced by the first image encoding method are denoted as S1-S10; The second image encoding method produces unnatural images, adding "A letter "in the code, that is, S1A~S10A.

 

Nature images contain the following characteristics:

 

(1) Image size

First encoding method: 2560pixels(L)X2048pixels(W)

Second encoding method: 1920pixels(L)X1536pixels(W)

 

(2) pixel color composition

In the image, the blue, magenta, yellow and black inks of each pixel are arranged in the same proportional order as the next adjacent pixel.

 

(3) Color sequence

Cyan, Magenta, Yellow, and Black.

 

(4) color value

The first encoding method: to 8-bit binary signal, linear collocation dot coverage percentage. When the digital signal is 28, the dot coverage percentage is 0%. When the digital signal is 228, the dot coverage percentage is 100%.

 

The second encoding method: to 8-bit binary signal, linear collocation dot coverage percentage. When the digital signal is 0, the dot coverage percentage is 0%. When the digital signal is 255, the dot coverage percentage is 100%.

 

(5) image reading direction

When the image signal is read, the reading direction starts from the upper left corner of the image and ends at the lower right corner. [next]

 

Unnatural images contain the following properties

In unnatural images, resolutionchart is used to evaluate the resolutionability of the image output device, the pattern of mesh, and various color effects.

colorchart is used to compare colors and correct errors.

 

Standard color images are stored in CD-ROM format (Electronicdata)

CD-ROM data format

The data stored in the CD-ROM contains 36 image file formats. The file name is selected according to the image name. Table2 shows the file name, size, length and width, and related image name.

 

TIFF(TaggedImageFileFormat) file format is jointly developed and developed by Microsoft and some other companies. Currently, it can be said that TIFF(TaggedimagefileFormat) is the standard of digital image format in the industry, with elasticity, extensibility, portability and supplement. As a result, more and more image processing vendors are adopting the TIFF file format, and more and more tools are available. But TIF files are not without their drawbacks. Because of their inclusive nature, TIF files are inherently complex and more difficult to administer or program than other file formats.

 

conclusion

The use of video and color images has increased dramatically as prepress operating systems have improved. This, coupled with the use of electronic, digital file exchange, has led to an astonishing growth in the development of image and color management systems and the trend towards post-press processes. Therefore, it is all the more important to understand the specifications of digital images.

 

The quality of a digital image can be evaluated by the prepress by comparing it to the original image. By changing the distribution of pixels, the quality of the scanned image can often be improved or even exceeded. Digital image quality is the result of a number of factors, including: the quality of the original scan image, scan resolution Settings, scan hardware equipment, operator skills, display resolution, gray balance, dot area rate, resolution, tone, natural color performance and so on. Therefore, the appropriate image quality should consider user needs, system requirements, network infrastructure, and price.

 

The evolution of digital information will significantly change the professional training of prepress operators. How to manage and store digital image files, open color management systems, and network transmission applications, all these have to follow the trend of transformation, to cope with the future.