Gray and color images

Images displayed on the computer are often displayed in binary, gray, pseudo-color, and real-color formats. Gray Scale and color format are the most common types of digital image processing. The various image processing algorithms involved in this book use these two types of images as the processing objects.

1. Grayscale Images

A grayscale image is the most basic form of a digital image. a grayscale image can be digitalized by a black or white image, or obtained from a color image by removing the color. A grayscale image only expresses the brightness information of the image without the color information. Therefore, each pixel of the grayscale image only contains a quantified gray level (that is, the gray level), which is used to represent the brightness level of the image, generally, one byte (eight binary digits) is used to store the gray value.

If the gray value is expressed in 1 byte, the positive integer range can be 0 ~ 255, that is, the pixel gray value ranges from 0 ~ Between 255, with a gray level of 256. Note that the gray-scale resolution capability of human eyes is usually between 20 and 20 ~ Level 60. Therefore, the gray value storage in bytes not only ensures the resolution capability of the human eye, but also conforms to the computer data addressing habits. In special applications, a higher gray level may be required. For example, the gray level of CT images is as high as thousands, and 12-or 16-bit binary digits are required to store data, however, these images are usually displayed and processed using dedicated display devices and software.

2. Color Image

Color Image Data not only contains brightness information, but also color information. The color representation method is diverse. The most common is the tri-base color model, such as RGB (red/green/blue, red/green), which can be mixed into any color. Therefore, the RGB model is used in a variety of color imaging devices and color display devices. conventional color images are also represented by RGB tricolor. Each pixel includes RGB tricolor data, each base color is represented by one byte (8-bit binary), and the data in each pixel is three bytes (24-bit binary ), this is what people often say about 24-digit real color.

Refer:

Xie fengying, Zhao danpei. Visual C ++ digital image processing. E-Industry Press. 2008. (http://book.51cto.com/art/200808/84606.htm)