参考网上的资料写的gif编解码。



编码用gdi解析常用图片格式，然后组装成gif

解码吧gif的每一帧转换成dib



gif文件格式网上有很多介绍



gif用的变长lzw压缩算法：

没弄懂原理，只知道过程。压缩取一个字符作为后缀，看看字符串是否存在。存在，用对应的编码作为前缀继续取；不存在把字符串添加到字典，前缀添加到输出流，后缀作为前缀继续取。解压取一个编码看看字典中是否存在。存在用对应的字符串的第一个字符作为后缀，看看当前字符串是否存在，不存在添加到字典中，后缀作为前缀，前缀对应的字符串添加到输出流，继续取；编码不存在，前缀对应的字符串的第一个字符作为后缀（这时当前字符串肯定不存在，字典中下一个可用编码肯定等于刚取出的编码），字符串添加到字典中，编码作为前缀，前缀对应的字符串添加到输出流，继续取。

编码流转换成字节流是按位从低到高的，window是小端模式（低字节在低地址），字节内低位在右边。



24位dib转换成8位dib时使用的八叉树算法



图片拉伸时参考的网上的双线性插值算法。

字典满了位数加一，位数是12时不加-Online reference materials written gif codec.



Encoded using gdi resolve common image formats, and then assembled into a gif

Each frame decode it into a gif dib



There are many online gif file format introduced



gif lzw with variable length compression algorithm:

Did not understand the principle, only know the process. Compression takes a character as a suffix, and see if there is a string. Exist as a prefix to continue to take with the corresponding encoding　there is no string to add to the dictionary, a prefix added to the output stream, the suffix as a prefix to continue to take. Take a look at extracting coding dictionary exists. Exist with the corresponding first character string as a suffix to see the current string exists, there is no add to the dictionary, the suffix as a prefix, the corresponding string to the output stream, continue to take　coding does not exist, prefix corresponding first character string as a suffix (when the current string certainly does not exis