Several color modes of the hottest digital image I

Several color modes of digital image (2)

in Photoshop Image processing software, there are 8 color modes, such as bitmap, gray scale, two tone, index, RGB, lab, CMYK, multi-channel, etc. there are some specific connections between them. Sometimes in order to output a printed document or need special processing of an image, it is necessary to convert from one mode to another mode

(I) RGB mode

the RGB mode of Photoshop uses the RGB model to assign an intensity value from 0 (black) to 255 (white) to the RGB component of each pixel in the color image. For example, a bright red may have an R value of 246, a g value of 20, and a b value of 50. When the values of the three components are equal, the result is gray. When the value of all components is 255, the result is pure white; When all values are 0, the result is pure black

rgb images use only three colors, reproducing up to 16.7 million colors on the screen. RGB image is a three channel image, so each pixel contains 24 bits (8 × 3)。 The default mode of new Photoshop images is RGB, and computer monitors always use RGB model to display colors. This means that when working in non RGB color mode (such as CMYK), Photoshop will temporarily convert the data into RGB data and then display it on the screen

the RGB model selected for RGB mode does not necessarily have to be CIE RGB model. It can choose one of the following RGB models

1, "sRGB" is used for standard RGB color space. This color space is adopted by a large number of software and hardware manufacturers, and has become the default color space for many scanners, low-end printers and software

2, "Apple RGB" is used for RGB color space used by previous versions of Adobe Photoshop and a large number of other desktop publishing applications. Apple RGB is a good choice for displaying images on Mac OS system

3, "CIE RGB" is used for RGB color space defined by CIE. This option provides a fairly wide color gamut, but it does not handle cyan well

4, "colormatch RGB" is used for the color space defined by radius company, which is consistent with the local color space of the company's pressview display

5, "NTSC (1953)" is used in the video color space defined by the National Television Standards Committee (NTSC). This is the earliest color TV standard, which has been mostly replaced by the latest smpte-c standard

6, "pal/secam" is used for the current color TV standards in Europe and other countries, where pal or SECAM standard TVs are used

7, "smpte-240m" is used for RGB color space of high-definition TV products (as opposed to broadcasting). It has a wider color gamut than the color space based on HDTV phosphor. If you need a wider gamut than many other color spaces (especially sRGB), this option is a better choice. It does not have to go to extremes to use wide gamut RGB

8, "smpte-c" is used for the current color TV standards in the United States and other countries, where NTSC standard TVs are used

9, "wide gamut RGB" is used for RGB space with a wide gamut defined by pure spectral primary colors. The color gamut of this space includes almost all visible colors, which is wider than the color gamut that a typical display can accurately display. However, many colors specified in this color gamut cannot be accurately reproduced on RGB display or how to buffer or print in the current situation

10. "Self defined" can create a self-defined RGB profile. If you have understood the description of the scanner RGB space and want to set the RGB color space of Photoshop, if the cost of the product is further reduced and the production of the same low iron aluminum is set as the company's first new profit and price growth point, this option will be very useful

the setting to store and load different RGB color models is to select "store" or "load" in the "RGB settings" dialog box, which means to store it as ICC profile

working in RGB mode has the following advantages:

1. Save memory and improve performance

2. It has greater device independence, because RGB color space does not depend on the display or ink. No matter the display, computer or output device is used, the correction of the image is retained