Photoshop channel mixer principle and calculation

Before learning the Photoshop channel mixer, we must understand the composition of colors and the principles of channels.

In the additive color system, "red + green = yellow", "red + blue = magenta" and "blue + green = cyan". In the monitor, RGB mode is used. All three RGB values ​​​​are 255, which is displayed as white, and all three RGB values ​​​​are 0, which is displayed as black. Any image in the channel is a grayscale image. White represents all selections, black represents no selection at all, and gray represents partial selection. This concept is very important in the creation of selections with the channel mixer and gradient mapping later. Once you understand these thoroughly, it is no longer difficult to use the channel mixer to cut out images.

This is the original picture:

Click on Photoshop's Layers panel, press the Create New Fill Layer and Adjustment Layer buttons, and select Channel Mixer.

Select the green channel from the output channel

Select the blue channel from the output channel

The output channel in the channel mixer is the channel we want to change. The red, green, and blue channel values ​​​​in the source channel are the channel values ​​​​that we participate in when modifying the output channel. Moving the source channel slider button will not change the gray color of the original channel. degree value. As you can see in the three pictures above, the output channel is red, the red channel value in the source channel is 100%, the output channel is green, the green channel value in the source channel is 100%, the output channel is blue, and the source channel is blue. The value in the blue channel is 100%. This is the projection of the monitor we just mentioned. If you move all the trichromatic value sliders in the source channel to 0, the image displayed on the monitor will be black!

As you can see, I used the color sampling tool to set three sampling points, selected red in the output channel, moved the value in the source channel to 0%, and the color of the image changed. The original red becomes black, and the entire image becomes cyan. This means that there are only green and blue in the channel, and the gray value of red is 0.

Continue, move the green channel slider in the source channel to 100%, and the color of the image changes! The original green banner becomes yellow! This is red + green = yellow!

Cancel all the settings just now. Let's understand the channel mixer from the channel panel and click to separate the channel.

Press the merge channel button again, select the mode as RGB color mode, press the OK button, and press the settings below

The image color has changed!