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数字灰度图像中邻近的像素倾向于具有相似的亮度。像素亮度一般情况下用普通二进制编码。然而,采用普通二进制编码,比特间的相关并不能反映像素亮度之间的相近度。本研究采用了格雷码而非普通二进制编码,并将图像分解为子图像(分别是2个、4个和8个)。每个分解后的子图像将分别用PPM压缩(PPM是一种基于背景的适应性数据无损方案)。该方案在8个自然场景图像中测试。结果显示同等条件下采用格雷码和像素分解提升了PPM压缩效果。
Adjacent pixels in digital grayscale images tend to have similar brightness. Pixel brightness under normal circumstances using ordinary binary encoding. However, using common binary coding, the correlation between bits does not reflect the closeness between pixel intensities. Gray code was used instead of plain binary code and the image was decomposed into sub-images (2, 4 and 8, respectively). Each decomposed sub-image will be compressed with PPM, respectively (PPM is a background based adaptive data lossless scheme). The program is tested in eight natural scene images. The results show that using the Gray code and pixel decomposition under the same conditions improve PPM compression.