sRGB color implementation method

The accurate reproduction of color has always been a headache. The use of terminal devices for various color images is extremely heavy. For example, monitors, digital cameras, scanners, printers, etc., how to make the colors consistent between devices It has increasingly become a research hotspot. sRGB is a color space definition that provides a standard way of defining colors so that external devices and software applications can use the same color description. With the wide application of sRGB in various color fields, it quickly became an international standard.

The origin of sRGB

For advanced printing and graphic design professionals, image display devices with relatively good color processing capabilities should be part of Apple Inc.'s device, in contrast to the company's ColorSync system, which is an operating system-class CMS ( Color Management System). Apple's products are very good in terms of performance, but they cannot be widely used on PCs. Microsoft took notice of this. In 1997, the company and Hewlett-Packard Co. created the sRGB color space, or "Standard Red Green Blne," or Standard RGB, which is a PC-based 32-bit color space.

When sRGB is used by digital image display devices such as monitors, scanners, printers, and video cameras, it can improve color matching capabilities between digital devices and printouts, ensuring consistent color. Before the sRGB technology was implemented in the PC, the effect of the color processing function of the Microsoft Windows operating system was not significant, but Windows 2000 provided the sRGB integration of the entire ICM2.0, making the sRGB color space rapidly popularized in the color display terminal.

sRGB color implementation method

Different devices use different mechanical devices to produce colors: the general printer is based on a subtractive color system, usually using cyan, magenta, yellow, and black, ie CMYK, starting with white and subtracting red, green, and blue to Get color and black; display color display is based on additive color theory, starting with black, starting to increase red, green and blue to get a variety of colors; sRGB color space is the use of many values ​​to accurately draw the color of red and green Blue elements, which are composed of these elements to form the pixels in the digital image and color areas such as images, diagrams, and texts, compensate for the differences in color appearance due to mechanical differences. The sRGB standard color space definition can meet the need to improve the exact color matching between software applications and hardware devices.

The deficiencies of sRGB

Since the gamma level affects the accurate reproduction of the midtones of the image, it is important to set a consistent gamma level between all devices. This is an absolutely necessary and important thing in properly managing the color flow. . If the gamma level between devices is inconsistent, it is impossible to correctly implement color reproduction between these devices. The de facto standard used by many image editing programs and display calibration systems when opening a picture is a gamma value of 1.8 as assumed in Mao OS. But sRGB on the PC uses a gamma of 2.2. Therefore, the matching of colors in a mixed environment of Macs and PCs and mixed software packages is not an easy task, which is one of the significant inconveniences that sRGB brings to operators.

In addition, although sRGB is a big improvement for PC users, most color experts still believe that sRGB has a fatal weakness: Compared with print media, the color range of displays is affected by color and hue. With severe limitations, the sRGB color workflow is generally not optimally reproduced. This is also the reason why the number of brands implementing sRGB in the display area is very small. However, in the area of ​​scanners and printers, after HP, almost all manufacturers have realized quickly.
sRGB requirements. The current solution to this more deadly problem also requires the technical efforts of numerous display manufacturers.

sRGB development prospects

Now, the alliance formed by Microsoft and Hewlett-Packard has released sRGB64. This standard adopts 64.
Bit to reproduce color, but not 32-bit. sRGB64 essentially doubles the accuracy of the color, with red, green, and blue values ​​below zero (no color) and above 1.0 (the largest possible color). This extra space allows for more precise operation of colors, in addition, using this method, the operator never loses information. If you compress the blue range in a 32-bit color image to zero, the blue tone range will become zero; if you need to restore blue, all the original tone expansion will disappear, and the resulting image will be You get a blue projection. But in the case of 64-bit pictures, all the blue tones still exist. That is, values ​​outside of the color range are not clipped, but are saved for future viewing and use, as well as other operations, without affecting the original image.

The current situation is: Although there are still some deficiencies in the sRGB color space, it also has its own many advantages. The sRGB's 2.2 gamma value has excellent perceptual coding capabilities, it can almost perfectly match the physical properties of computer and video displays, and is a presumed gamma point for various versions of Windows, which makes sRGB to manage various color images. A good application for graphics applications and print colors.