dct变换与dct逆变换，程序可以直接运行，代码中有详细注释，容易理解。-dct dct transform and inverse transform, the program can run the code in detail in notes, easy to understand.

该程序功能为对图像文件进行DCT变换，和系数置零后的重构。-The program functions as a DCT transform of the image file, and the coefficient of zero after reconstruction.