What is RGB?

RGB (Red Green Blue) refers to the color composition in terms of the density of the main colors from which the colors are created.

What is RGB (Red Green Blue) Model?

It is a color model based on additive synthesis where it is possible to represent a color by mixing it by adding three main light colors.

The RGB color model does not exactly define what red, green, or blue means, so the same RGB values ​​may show markedly different colors on different devices using this color model. Even if they use the same color model, color spaces can vary significantly.

Ratios in which Every Color is Blended

To indicate the ratio at which each color is mixed, a value is assigned to each of the primary colors, so the value of 0 means that it does not interfere with the mixture, and it is understood that it contributes to more intensity as the value increases.

Although the range of values ​​can be any value (actual values ​​between 0 and 1, integer values ​​between 0 and 37), it is common for each primary color to be encoded with one byte (8 bits). Thus, as usual, the density of each component is measured on a scale ranging from 0 to 255.

Therefore, red with (255,0,0), green with (0,255,0), and blue with (0,0,255), in all cases a resulting monochrome color is obtained. The absence of the color known as black is achieved when the three components are 0, (0,0,0). The combination of two colors at level 255 with a third color at level 0 causes three intermediate colors.

Thus, it is yellow (255,255,0), cyan (0,255,255) and magenta (255,0,255). Obviously, the white color is created at the maximum level (255,255,255) with three primary colors.

All colors can be represented in a cube, and each color is a spot on the surface or inside. Grayscale is located on the diagonal, which combines white with black.

Color on Computer Screens

The feeling of color on computer screens is produced by the additive mixture of red, green, and blue. There are a number of small dots called pixels. Each dot on the screen is a pixel, and each pixel is actually a set of three subpixels; one is red, one is green and one is blue, each shining at a certain intensity.

Initially, the limitation in the color depth of most monitors led to a range limited to 216 colors defined by the color cube. However, the predominance of 24-bit monitors made it possible to use 16.7 million colors from the HTML RGB color space.

The web’s color palette consists of 216 combinations of red, green, and blue where each color can get a value between six different colors (hexadecimal): #00, #33, #66, #99, #CC or #FF. You can see that 63 gives the number of 216 combinations.

These decimal values ​​correspond to 0, 51, 102, 153, 204, and 255, the density percentage of which is 0%, 20%, 40%, 60%, 80% and 100%, respectively. This allows 216 colors to be divided into size 6 cubes.

The more saturated the pixels are, the better, but it’s definitely not a pure color. Therefore, the production of colors with this system has two limitations:

• A derivative of the work of the admixture mixtures: only the inner colors of the triangle formed by three light sources can be obtained.
• The derivative of the fact that the main colors used are absolutely not monochrome.
• In addition, besides being configurable by users where various screens can change, various screens are not exactly the same.

This means that color coding for screens should be interpreted as relative descriptions and accuracy should be understood based on the characteristics of the screen.

Color Perception and Feeling

The eyes have two types of photosensitive cells or photoreceptors: rods and cones. The second is responsible for providing color information.

To know how a color is perceived, it should be taken into account that there are three types of cones with different frequency responses and that they have maximum sensitivity to the colors that make up the RGB, red, green, and blue triplets.

Cones receiving information from green and red have a similar sensitivity curve, while the response to blue is the twentieth (1/20) portion of the response to the other two colors.

This fact is used by some image and video encoding systems, such as JPEG or MPEG because they consciously “lose” more information about the blue component because the eyes will not perceive this loss.

The sense of color can be defined as the response of each of the sensitivity curves to the spectrum emitted by the observed object. In this way, three different answers are obtained, one for each color.

Achieving the color feeling in this way means that two observed objects emitting a different spectrum can produce the same feeling.

And upon this limitation of human vision, it is based on the visual synthesis studied and the color synthesis model in which it is possible to obtain the color of a particular spectrum object, a mixture of three primary colors.

Brightness Signal

The sense of brightness is given by the brightness and opacity of an object, and two objects with different shades and prisms can produce the same feeling of light. The brightness signal is the quantity of this brightness feeling.

To ensure compatibility between black and white images and color images, existing television systems (PAL, NTSC, SECAM) transmit three information: brightness and two color difference signals.

In this way, older black and white models can ignore color information and produce only the brightness, that is, the brightness of every pixel applied to a grayscale image.

And color televisions receive the information of three RGB components from a matrix that associates each component with one of the color difference signals. They are transmitted differently for each of the television systems, so a PAL replication system may have trouble producing an NTSC signal.

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