RGB color Mode

We use a magnifying glass to view the computer monitor or TV screen, you will see a large number of red-green blue three color of the dots. The left image below is the local enlargement of the left image. All the colors on the screen, that is, all the image content we see, are reconciled by them.

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Now we open the image in Photoshop as shown in the left, open the way is through the menu "file _" or use the shortcut key 〖ctrl_o〗 (the description of the shortcut will appear in a later course, it is not clear that it does not matter). You can also drag images directly from the Windows directory to Photoshop. If the Photoshop window is obscured or minimized, you can also drag it to the button on the taskbar, and then drag it to the window when the Photoshop window pops up.
Press 〖f8〗 or from the menu "window _ Info" to bring up the information palette. The image below is shown below. Then try moving the mouse in the image, and you will see that the values are constantly changing. Note that when you move to the blue area, you will see a higher value for B, and a higher value for r when moving to the red area.

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All the colors on the computer screen are made of three shades of red green and blue , which are mixed in different proportions. A group of Red Green Blue is a minimal display unit . Any color on the screen can be recorded and expressed by a set of RGB values. So, the leftmost picture seen below is actually made up of three parts on the right side.

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So this red Green Blue is also called the RGB Light, in English is R (Red), G (green), B (blue). RGB can be imagined as the Chinese food inside the sugar, salt, msg, any dish is mixed with these three kinds of spices.
In the production of different dishes, the proportion of the three are not the same, and may even be different. So different images, RGB components are not the same, there may be some of the graph R (red) components more, some B (blue) components more.
When cooking, the recipe will prompt similar to "Sugar 3 grams, salt 1 grams" and so on, to show how much seasoning, in the computer, RGB so-called "how much" refers to the brightness, and use an integer to represent. Typically, RGB has 256 levels of brightness, expressed as a number from 0, 1, 2 ... Until 255. Note that although the number is up to 255, 0 is also one of the values, thus a total of 256 levels. It's like 11 from 2000 to 2010.
According to the calculation, the RGB color of level 256 can combine about 16.78 million kinds of colors, namely 256x256x256=16777216. Usually also referred to as 16 million or tens of thousands of colors. Also known as 24-bit color (2 of the 24-time Square).

This 24-bit color also has a more bizarre name is 8-bit channel color, why so called?
Here the so-called channel, in fact, refers to three kinds of light color of the respective brightness range, we know its range is 256,256 is 2 8 square, called the 8-bit channel.
Why do you always use 2 of the time to express? Because the computer is 2-binary, it uses 2 of the time to express the number of colors and some other quantities.

The color channel here is conceptually not a specific thing. We can compare the Mihara shade to three adjustable light lamps of different colors, then the channel is equivalent to the dimming button. For viewers, it's just the image itself, not how the three kinds of shade mix. Just as you care about the performance of the actors in the movie, you don't think about the process of directing the shots. Thus, the function of the channel is "control", not "presentation".
The above is the color channel, and the image channel in the following tutorial is not exactly the same concept.

The support for 16-bit channel colors has been enhanced since the Photoshopcs version, which means that more colors can be displayed (i.e. 48-bit colors, about 281 trillion). RGB has a single luminance value of 2 of 16 square, equal to 65536,65536 three is 281474976710656. But the number of colors that can be distinguished by the human eye is less than 24-bit 16.78 million colors. So the higher the number of colors in the eyes of the people there is no difference.

A color, such as r32,g157,b95, or r32g157b95, can be expressed using the letters R,G,B plus their respective values. Sometimes for the sake of convenience also omit the letter write 32,157,95 (delimited symbol is not marked wrong). Then the order of representation is RGB. There is also a 16-binary representation that will be described later.

So how do these numbers and colors correspond, or how do you figure out what color to look like in a set of numbers?
In fact, judging the color directly from the values is difficult for beginners or even veteran. This requires a certain amount of experience to consider the mixing of three kinds of shade. But this ability is not a must. Even if you can't do it, it will hurt you later.

For a single R or G or B, when the value is 0, the color does not glow, and if 255, the color is the highest brightness. This is like dimming the lamp, the number 0 is equal to turn off the light, the number 255 is equal to the dimming knob to open to the maximum.
Now leave the tutorial and think about it: How much is black, white, red, green, blue, and yellow RGB values on the screen?

After thinking, we open Photoshop, bring up the color palette 〖f6〗, and click on the color block at the Red Arrow. This is shown in the left. This color block represents the foreground color. The other color block at the bottom right represents the background color. Photoshop default is the foreground color black, background white. The shortcut key 〖d〗 can be reset to the default color.
If the color palette is not RGB, you can click on the color palette in the upper right corner of the small triangle button, in the pop-up menu, select the RGB slider, as shown in the right image.

Pure black, because there is no shade on the screen. The equivalent of RGB three colors are not illuminated. So the black RGB value on the screen is 0,0,0. We can adjust the slider or directly enter the number, you will see the color block becomes black. This is shown in the left.
But the white is opposite, is the RGB three kind of shade all sends to the strongest brightness, so the pure white RGB value is 255,255,255. The following figure.
The most red, means that only red exists, and the brightness is strongest, green and blue do not glow. So the most red value is 255,0,0. The image below is shown below.
Similarly, the most green is 0,255, 0, and the most blue is 0, 0,255. Did you do the right thing? If not, repeat the previous lesson.

So what's the most yellow? RGB does not contain a yellow item AH. Let's put the question aside for the moment, we'll look at the hue spectrum of the color. This is shown in the left.
The so-called Hue refers to the color of the kinds of colors, respectively: Red orange yellow green cyan blue purple. These seven colors are connected to each other to form a closed ring. 0-degree starting point in X-axis direction, unfolded counterclockwise. The image below is shown below.
In this ring, the two colors at the angle of 180 degrees (that is, the color at the ends of a circle's diameter), are called invert colors, also known as complementary colors. The complementary color between the two is the relationship between this, and now we fill the middle of the ring, as shown in the left. Assuming that the small box currently in the center of the circle is the color we want to select, the small box moves toward the blue while moving away from the yellow, or close to the yellow and away from the blue. Just as it is impossible to walk both sides at the same time on a seesaw, you cannot approach yellow and blue at the same time.

In the middle is white, you can see, if you want to get the most yellow, you need to color box to the most yellow direction, but also gradually away from the most blue. When we reach the edge of the yellow part of the ring, it is the most yellow, and we are farthest from the most blue. As a result, yellow = white-blue ". Why not white + yellow? Because the blue is the primary color of light, to the original shade adjustment to prevail. Therefore, the most yellow value is 255,255, 0. The image below is shown below. can also be obtained: pure yellow = pure red + pure green.
If an image on the screen is yellow (especially on the screen, the print is different), it cannot be said that there is too much yellow light, but it should be said that there is too little blue light.

Looking at the chromatographic ring again, we can visually highlight the respective invert colors of the three primary colors. Red to cyan, green to magenta, blue to yellow. Such as.
In addition to visual inspection, you can also calculate the inverse color of any one color: first get the RGB value of this color, and then subtract the existing RGB values by 255. For example, the yellow RGB value is 255,255, 0, then calculated by: R (255-255), G (255-255), B (255-0). Complementary colors are: 0, 0,255. It's blue.

For an image,
If you increase the brightness of r alone, the amount of red light increases. Then this image will be reddish.
If you increase the brightness of B alone, the amount of blue light increases. Then the picture will be blue.

Through the above, we have described the concept of RGB color, of course, we will also introduce the other color patterns later. But keep in mind that RGB mode is the physical color mode of the display. This means that no matter what color mode is used in the software, as long as it is displayed on the display, the image will eventually appear in RGB mode. Therefore, using the RGB mode is the fastest, because the computer does not need to handle the additional color conversion work. Of course, this speed difference is difficult to detect, but theoretically.

RGB color Mode