RGB Compression. A color image usually consists of highly correlated RGB components which are unable to be differenciated by a human’s visual capability. An 8-bit color table, i.e., a maximum of 256 colors, is often good enough to make a decent color image presentation. A RGB compression is a mapping of a 3-d color space to a 1-d color index image. It provides an effective way to reduce the original image size for efficient image presentation and comunication. The XBit’s command rimage gisoc is a useful tool to conduct a RGB compression. The simpliest syntax of this command is
rimage gisoc -in inputImage -out outputImage -nc nColors
The following images show six color index images in 256, 128, 64, 32,
16 and 8 colors. All images are compressed from a 24-bit RGB image by the
command rimage gisoc. The total number of colors in the original
24-bit RGB image is 23695.
256 colors |
128 colors |
64 colors |
32 colors |
16 colors |
8 colors |
The raw image can be downloaded from the zip file pea.zip. The original results were in DIB format and can be download from the zip file peabmp.zip. Note: pea256.bmp was created with a request of 256 colors, but the resulted image only got 202 due to merging processing controlled by the default excluding parameter.