说明：  本实验要求将任意一个RGB图像转换为web-safe RGB图像，并要求将图6.8转换为web-safe RGB彩色图像，图像的原始格式为jpg格式，要求将结果图像也转换为jpg格式。该实验中首先编写把RGB图像转换为web-safe RGB图像的通用程序，然后调用这个程序实现对图6.8的转换。
(Requirements of this experiment will be any RGB image is converted to web-safe RGB images, and requested that the map 6.8 converted to web-safe RGB color image, the image of the original format for jpg format, also called for the results of the image converted to jpg format. First of all, the preparation of the experiment the RGB image is converted to web-safe RGB image of the general program, and then call the procedure to achieve the conversion of Figure 6.8.)