An adaptive multi-dimensional discrete cosine transform (multi-D DCT) algorithm are proposed in order to obtain high compression for still color image under high signal-to-noise ratio. In this algorithm

the original image is splitted into non-over-lapped 8х8 blocks. Then the statistic characteristic of each block is calculated and assess the abundance of inner information in each block based on averages and variances. To the block of which the inner information is abundant

correlations between adjacent pixels of each block and YUV channels of color space are exploited through 3-dimensional discrete cosine transform(3-DDCT);To the block ofwhich the inner information is not

correlations among adjacent pixels of each block

YUV channels of color space and adjacent blocks are exploited through 4-dimensional discrete cosine transform(4-D DCT). The transform coefficients are coded by quantization further. Experimental results have proved that the proposed algorithm can achieve higher compression ratio and ThePSNR(average Peak Signal-Noise-Ratio) of reconstructed image is higher than by JPEG.