计算GIF彩色图像的差异，两幅图像大小一致且调色板一致。其中Psnr 为两幅图像的psnr值.P 为两幅图像之间像素索引不同的索引值占图像大小的比例。-GIF image color difference calculation, the two images the same size and same color palette. One Psnr the two images psnr value. P index for the pixels between two images, the index values of different ratio of total image size.