Color Principle, three-color principle and HLS (color phase, brightness, saturation) Principle

When talking about painting and images, we can't go without talking about color. All the patterns are made up of basic shapes and colors. colors constitute an important part of our image processing. Next we will understand the color principle, it will be the basis of our art.

(1) three-color Principle

In the physics class of middle school, we may have performed a prism experiment. After the white light passes through the prism, It is decomposed into various colors and the chromatography gradually transitioned, the colors are red, orange, yellow, green, blue, and purple in sequence. This is the visible spectrum. Human eyes are most sensitive to red, green, and blue. human eyes are like a three-color receiver system. Most colors can be synthesized by Red, green, and blue according to different proportions. Similarly, the vast majority of monochrome light can be divided into three colors: Red, green, and blue. This is the most basic principle of color learning, that is, the three-color principle. The three base colors are independent of each other, and neither of them can be synthesized. Red, green, and blue are the three base colors. These three colors are the most widely used colors. Red, green, and Blue Base colors are added according to different proportions to form a mixed color.

Red + Green = yellow

Green + Blue = blue

Red + Blue = Magenta

Red + green + Blue = white

Yellow, blue, and magenta are both mixed with colors, so they are also called the secondary colors. In addition:

Red + cyan = white

Green + Magenta = white

Blue + yellow = white

Therefore, the blue, yellow, and magenta colors are red, blue, and green respectively. Because each person's eyes have different feelings for the same monochrome, if we use a mixture of three basic colors of the same intensity, we assume that the intensity of white light is 100%. At this time, people's subjective feelings are, the green light is the brightest, the red light is the second, and the blue light is the weakest.

In addition to the addition and mixing method, there is also the subtraction and mixing method. Under the white light, the blue pigment can absorb the red and reflect the blue. The yellow pigment absorbs the blue and reflects the Yellow. The red pigment absorbs the green and the red. That is:

White-red = cyan

White-Green = Magenta

White-Blue = yellow

In addition, if the blue and yellow pigments are mixed under the white light, because the pigment absorbs the red and blue colors, and reflects the green color, the pigment mixture is shown as follows:

Pigment (Yellow + Cyan) = white-Red-Blue = green

Pigment (magenta + Cyan) = white-red-green = blue

Pigment (Yellow + Magenta) = white-green-Blue = red

The above are all subtraction and Mixing colors, which form different colors by absorbing different proportions of the three base colors. Therefore, the blue, red, and yellow colors are called the three basic colors of pigments. The color mixing of three colors is widely used in painting and printing. In the three base colors of pigments, the three colors of red, green, and blue are called secondary colors of subtract or pigments. There are:

(Cyan + yellow + Magenta) = white-red-blue-green = black

The color mode represented by the above three colors is called the RGB mode, while the color mode represented by the principle of the three colors is called the CMYK mode, which is widely used in painting and printing.

RGB mode is the most commonly used color mode for drawing software. In this mode, it is easier to process images, and the RGB storage images are smaller than those of CMYK images, memory and space can be saved.

CMYK mode is a pigment mode, so it belongs to the printing mode, but it is essentially no different from the RGB mode, but it only produces different colors. RGB is the addition and mixing mode, while CMYK is the subtraction and mixing mode. For example, the display adopts the RGB mode because the display emits light from the fluorescent material on the fluorescent screen by using an electronic beam to produce color. Black when there is no light, white when the light is added to the maximum. What about printers? Its ink does not emit light by itself. Therefore, only the colors that absorb specific light waves and reflect other light must be reduced.

(2) Principle of HLS (color phase, brightness, and saturation)

Hls is hue, luminance, saturation ). Color is a property of color. It is essentially the Basic Color of color, which we often talk about seven colors: red, orange, yellow, green, blue, and purple, each color represents a color phase. The adjustment of the color is to change its color.

Brightness is the brightness of the primary colors (for example, the primary colors of RGB Images are R, G, B, or various colors). brightness adjustment is the brightness adjustment. The brightness ranges from 0 to 255, and is divided into 256 levels. The gray images we usually talk about are divided into 256 levels of brightness between pure white and pure black, that is, from white to gray, and then to black. Similarly, in RGB mode, it represents the darkness of a primary color, that is, the darkness of the three primary colors, from light to deep.

Saturation refers to the color of the image. For each color, there is a set of standard colors. saturation is a physical quantity that describes the degree of closeness between the color and the standard color. Adjusting the saturation is to adjust the color of the image. When the saturation bar of an image is set to zero, the image becomes a grayscale image. You can try to adjust the saturation button on the TV.

Another concept is contrast. Contrast refers to the difference between different colors. The greater the contrast, the greater the difference between the two colors. On the contrary, the closer the two colors are. For example, when a grayscale image is raised, its contrast is more black and white. When it is adjusted to an extreme, it becomes a black and white image. On the contrary, we can get a gray canvas.

We understand the color principle, so we will not be confused in image processing, and we can adjust the color more quickly and accurately.

It can be seen that when the brightness value of the color (color-colored phase, saturation, brightness three basic parameters) is always 100%, the red channel for different saturation color blocks, the color block is always white, while the color block is different for different brightness when the saturation is always 100%. Therefore, we can conclude that:
The gray scale in the channel stores the brightness value of the color. Any image can be divided into three channels: Red, green, and blue. Each channel records the content of the three basic colors (expressed in brightness ), the high brightness of a channel indicates that the image contains many basic colors.
In fact, the gray scale is only different in brightness. The gray scale is usually expressed as a percentage relative to the "Black.

For the red color, the red channel stores the red "brightness" information, while other channels store the red "saturation" information through "grayscale.