（Discrete Cosine Transform，简称DCT变换）是一种与傅立叶变换紧密相关的数学运算。在傅立叶级数展开式中，如果被展开的函数是实偶函数，那么其傅立叶级数中只包含余弦项，再将其离散化可导出余弦变换，因此称之为离散余弦变换。-(Discrete Cosine Transform, DCT-short) is a Fourier transform is closely related with the math. In the Fourier series expansion, if the function is being expanded real even function, then its Fourier series contains only cosine terms, then the discrete cosine transform can be derived, so called discrete cosine transform.