基于小波变换的图像分级压缩算法

Image level compression algorithm based on wavelet transform

综合已有图像压缩算法优势,提出一种新的图像压缩算法———基于小波变换的图像分级压缩算法。将待压缩图像按频率高低分成若干子图像,根据各子图像包含能量的多少将它们分成3个等级,分别采用了不同的压缩算法。包含能量最多的低频子图像称为第1级,采用无损差分脉冲编码调制方式;包含能量较少的高频子图像称为第2级,采用嵌入式零树编码方式;包含能量极少的更高频子图像称为第3级,因其包含的能量极少,不再编码。其优点是压缩比高、算法简单、传输和下载速度快,在传输过程中可随时结束编码而不影响图像质量。

Synthesizes the advantages of image compression algorithm and puts forward the new image compression algorithm Image Level Compression Algorithm based on Wavelet Transform. To begin with, the image to be compressed is divided into sub-images according to the frequency. Then the sub-images are divided into three different levels, and different compression methods are adopted respectively according to the energy of the sub-images. Differential Pulse Code Modulation is adopted for the low-frequency sub-images with most energy, which are called the 1st level. Embedded Zero-tree Wavelet coding is adopted for the high-frequency sub-images with less energy, which are called 2nd level. Higher-frequency sub-images with lest energy, which are called the 3rd level, is encoded no longer. Here are the advantages： high compression ratio, simple algorithm, fast transmission and downloading speed, having no effect on quality of images when you complete encoding at any time on the course of transmission.