彩色图像三维六边形离散余弦变换编码

Three dimensional hexagonal discrete cosine transform for color image coding

为了适应人眼视网膜细胞的正六边形结构的排列方式并充分利用彩色图像各颜色分量间的相关性,提出了一种基于六边形采样的三维离散余弦变换方法。该方法根据传统的矩形采样和正六边形采样之间的关系来完成两者的转换;然后在已有的六边形离散余弦变换的基础上提出三维六边形采样的离散余弦变换,并验证它的能量集中性。最后,在同一个模型下建立彩色图像的空间位置和颜色分量,并利用提出的方法分别以不同的子图大小对不同的图像进行整体变换。实验结果表明:相对于传统的矩形采样,提出方法的压缩比提高了约51.1%,峰值信噪比提高了约16.3%,从而有效地降低了彩色图像各颜色分量间的相关性。得到的结果表明,利用六边形采样技术可以提高采样率,降低编码速率。

A three-dimensional（3D） Discrete Cosine Transform（DCT） method based on hexagonal sampling was proposed to fit the arrangement of hexagonal structure of the human retinal cells and to take advantage of the correlation among each color component of the color images. The method com- pleted the conversion between the traditional rectangular sampling and hexagonal sampling according their relationships. Then, it proposed 3D Hexagonal sampling DCT（3D HDCT） on the basis of exist- ing HDCT and verified its energy concentration. Finally, the spatial positions and color components of the color images in the same model were established, and the different images were transformed with different sub-plot sizes in a whole way by proposed method respectively. Experimental results show that the proposed method increases the compression ratio about 51.1 % and the Peak Sigal to Noise Ratio （PSNR） about 16.3% as compared with that traditional rectangular sampling method, respec- tively. The results decrease the correlation among color components of color images effeCtively, and demonstrate that hexagonal sampling applied to image coding can improve sampling rates and decrease coding rates.