利用matlab的DCT2函数，对图像做变换并压缩。并用8*8对图像分块，对每一块计算均方值作为阈值。,DCT2 use the matlab function, and transform the image so compressed. And 8* 8 image block, a calculation of each mean square value as a threshold.

A matlab program that implements the 2D DCT equation. Compares the results with the built-in function output for correctne-A matlab program that implements the 2D DCT equation. Compares the results with the built-in function output for correctness