(4) At present, for newspaper publication, the pictures used need to be retained for a long time. It is ideal to retain the picture data in RGB mode. After the correction and correction of the RGB mode picture data information can become a long-term storage of valid documents, so that future retrieval of RGB mode pictures from the archive can be known on different output devices. For RGB mode image data information to be reused in many future publishing workflows, it is very convenient whether the color separation method uses the system-level color management method or the image conversion method in Photoshop. (5) When printing, proofing, and outputting pictures using various printers, digital proofing devices, or computer monitors, the main method for observing (and measuring) the color difference of pictures reproduced by the above printing output devices is to measure the generation of neutrality. The amount of cyan, magenta, and yellow required for ash is printed as the gray balance of the replication system. If the picture is converted to CMYK mode, when the different output devices are reused, the picture needs to adjust the highlight, midtone, and dark tone points of the CMYK picture and change the total gray balance and color saturation. In order not to affect the print quality of the picture, the amount of black in the picture has to be changed, but if the picture is printed without correcting the black data, a bad print result will be produced. For example, a CMYK-mode image that was originally color-separated by a high-quality sheet-fed press would have a larger amount of ink in the picture if it was printed on a web press. The processing method could only be to modify the CMYK mode picture. The RGB mode picture can use a larger RGB tone range to reproduce brighter, more saturated colors. However, after the picture is separated into CMYK, all the pixels in the picture are within the CMYK tone range. As can be seen from the above discussion, using Photoshop to process color pictures should be done using RGB mode as much as possible. However, during operation, it should be noted that the pictures processed using the RGB mode must ensure the authenticity of the picture colors when outputting in the CMYK mode, and the processing of the pictures using the RGB mode must ensure that the pictures are completely processed and then converted into CMYK mode pictures. It is best to leave a picture in RGB mode for backup. In addition to processing images in RGB mode, Photoshop's Lab color mode also has good features. The RGB mode is based on the optical principle, and the CMYK mode pigment reflects the color mode of the light. The advantage of the Lab mode is that it compensates for the lack of the previous two color modes. RGB has too much excess color between blue and green, too little color between green and red, CMYK mode loses more color during editing and processing of pictures, and Lab mode has these aspects Compensated. The Lab mode is composed of three channels. The L channel represents the brightness, which controls the brightness and contrast of the picture. The colors included in the a channel range from dark green (low brightness value) to gray (middle brightness value) to bright pink (high brightness value). The b channel includes colors ranging from bright blue (low brightness) to gray to yellow (high brightness). Lab mode is similar to RGB mode, and a mixture of colors will produce brighter colors. Only the value of the luminance channel affects the light and dark changes in color. The Lab mode can be thought of as the RGB mode of two channels plus a luminance channel mode. The Lab mode is device-independent and can be used to edit and process any picture (including grayscale pictures), and is as fast as the RGB mode and several times faster than the CMYK mode. Lab mode guarantees that there is no loss of color in the CMYK range when the color mode conversion is performed. If you convert an RGB mode picture to CMYK mode, you should add a step to the operation step, that is, convert to Lab mode. In the non-color typesetting process, it is often used to convert a picture into a grayscale image using the Lab mode. For some images downloaded on the Internet in RGB mode, if you do not use Lab mode transitions and convert them to grayscale images, then sometimes you cannot typeset the pictures when you use the Founder Feiteng or the Verithek publishing software to typeset. It can be seen that when editing and processing pictures, try to use Lab mode or RGB mode as much as possible, and change to CMYK mode when it is a last resort. Once you have converted to a CMYK model image, you should not make it easier to turn it back. If it is really needed, it will be converted into a Lab model image. If the original picture used for the scan input is a color picture, but the picture is used in the grayscale layout, when the picture is input with the scanner, the original picture should not be directly input as the grayscale mode, and the picture should be input with the RGB mode. After the RGB mode has processed the picture, it will be converted into a Lab mode picture first, and then the channel separation command will be used to select the L channel picture as a grayscale picture for printing. Most operators in the process of actually processing pictures are relatively straightforward. What kind of pictures are required to be directly scanned into the desired picture mode with a scanner, and then used for typesetting after being processed slightly. It will still be the case. In fact, if you want to really get a good picture printing effect, do not be afraid of trouble, according to the standard operating procedures. (Finish)