【LibJPEG专题系列二十一】高于8位精度的压缩

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                                 Section 21—高于8位精度

    基线JPEG以每种颜色样本8位的形式来存储图像，换言之，RGB图像是每像素24位，灰度图像
是8位/像素，CMYK图像是32位/像素，等等。需要更高精度的应用则存储12位/样本的扩展。比
如，医学图像通常是12位灰度级别的。然而，12位的扩展并没有得到广泛的支持。支持它的则是
免费的IJG源代码（可见于part 2, item 15）。

    对于无损JPEG，其标准允许2到16位/样本之间的任何数据精度，但相对于高精度的有损JPEG，
高精度的无损JPEG则更少的广泛支持。据报道，斯坦福PVRG编解码器（见part 2, item 15）支持高
至16位/样本的无损JPEG。

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       Section - [21] What if I need more than 8-bit precision?


Baseline JPEG stores images with 8 bits per color sample, in other words 24 bits per pixel for RGB images, 8
bits/pixel for grayscale, 32 bits/pixel for CMYK, etc.  There is an extension that stores 12 bits/sample for
applications that need higher accuracy.  Medical images, for example, are often 12-bit grayscale.  The 12-
bit extension is not very widely supported, however.  One package that does support it is the free IJG source
code (see part 2, item 15).


For lossless JPEG, the standard permits any data precision between 2 and 16 bits per sample, but high-
precision lossless JPEG is even less widely supported than high-precision lossy JPEG.  The Stanford PVRG
codec (see part 2, item 15) reportedly supports up to 16 bits/sample for lossless JPEG.