Method and system for compressing and decompressing BMP picture file

The invention is applicable in the technical field of image processing, and provides a method and a system for compressing and decompressing a BMP picture file. The compressing method comprises the following steps: reading a bitmap file header, a bitmap information header and a color table of the BMP picture file; writing the bitmap file header, the bitmap information header and the color table into a compressed file; and reading bitmap data of the BMP picture file sequentially, writing a color value of image pixels and corresponding Num value thereof into the compressed file, and only writing one color value and the corresponding Num value which is the number of the continuous same color value when writing a plurality of continuous same color values. The compression method not only can achieve the aim of compressing the BMP picture, but also has a simple algorithm, and small operation amount.