Getting Started with Image Formats - Color Space

Color frequency and space

The image displayed on the computer is nothing more than a combination of colored dots. But in computer binary languages, what is the difference between red or purple? It does not make any sense to the computer. So how does the computer recognize different colors? The answer lies in the fact that each visually-related hardware and software uses a particular color space—a way to represent colors in numbers.

Our most common color space representation is RGB, because our display also uses this color representation. Our monitors project different intensities of red, green, and blue light on the screen - so RGB can exhibit full tone and light and shade. RGB represents various colors in 3 numbers, which we call color frequency. These color frequencies define red, blue, and green in different degrees from 0 (black) to 255 (saturation).

You can combine these different color frequencies to create new colors - just like blending pigments. Mixing red and green light will produce yellow light; mixing green and blue light will become blue light and mixing blue light and red light will appear purple light. If you mix two different color frequencies together, you create a third new color between the two. (For example, mixing 255 red with a little green will appear orange).

The color mixing shown above can create a pure and bright tone. Randomly mixing three colors with the same value among the three color frequencies of RGB will result in achromatic color with different levels of color from black (when 3 colors are 0) to white (3 colors with 255 colors). Therefore, the closer the RGB 3 values ​​are, the closer to no color: while increasing the same RGB value, it will be closer to white, making the image appear grayer. Any decrease of the more prominent RGB values ​​in the image will make the color darker and the image will become darker. To sum up the above two points - what happens when we set all the RGB values ​​below 0 to 255? - The color will be close to gray, and the color of the image will become softer.

If you are already very accustomed to using RGB, then when you need to use certain colors, you can find it immediately by intuition.

Other color spaces

Most drawing tools include HSB adjustments (hue-saturation-brightness) to make it easier to understand the principle of color mixing. Hue refers to the position where the red coordinate is 0, the green coordinate is 120, and the blue coordinate is 240 on a 360-degree color wheel. Saturation and brightness are expressed as percentages - 100% saturation and brightness present pure shades, and both are reduced to 0 after adding black and white, respectively.

Compared to RGB, CMYK is a method in which the colors printed on paper are unequally sized with cyan, magenta, blue, and black CMYK. The four-color color accuracy is higher than many displays can achieve, so it is very Suitable for high-quality print works.

Color Depth

RGB divides each color frequency into 0 to 255 different color levels, because this is the limit that can be obtained by 8 bits, and 8 bits can form 1 group. The amount of data used to represent the color becomes the color depth.

When we are dealing with pictures used on web pages, the color depth is particularly important for the following two items: one is the color depth of the display, and the other is the color depth of the file when the image is stored. The color depth of the display varies depending on the capabilities supported by the hardware display device and the structure of the software driver. The operating system usually allows the user to set the desired color depth in the display settings of the control panel. The color depth of the file varies depending on the file format when the image is stored.

Full Color

Although the typical typical RGB uses three 8-bit color frequencies, you can also change it to 24-bit color depth. At this time, we will be 24 bit of the shameless province of H  南 允 允 髂 髂 髂 髂 既 既 既 既 既 叵 叵 叵 隼 ǔ ǔ ǔ MǔN 颐 梢 梢 梢 谙 谙 谙 谙 谙 谙 柚 柚 柚There are 6,777,216 colors, but it is usually expressed in "million colors". Similarly, full-color images can faithfully record all colors.

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Full color contains far more hues than the human eye can discern, so most operating systems offer 16-bit high-color options (in the Macintosh operating system, they are "thousands of colors") . In fact, in high-color, the monitor can only show 32 different levels of red, 32 blue, and 64 green. These different levels of red, blue, and green are almost indistinguishable visually, but if we reduce the color depth to 16 bits per pixel, we can see the difference in color. And when the computer's display system sets a high level of color, it does not affect the quality of the image: Most drawing programs such as Photoshop or the browser still use 24-bit values. These color data are only cut off when viewed on the monitor. This is why high-color images have not been universal.