CIE XYZ Colour Space Used for Image Compression

In non-reversible coding of colour images, a suitable colour space conversion will improve the compression ratio. A new method is proposed for compressing CMYK images, using the Neugebauer equations to convert from the CMYK space to the CIE XYZ space. The images are then converted from XYZ TO THE YUV 4:2:2 colour space proposed in the JPEG/ADCT standard. The inverse mapping from XYZ back to CMYK is done by an iterative method. Using these colour space conversions, the compression ratio may be roughly twice as high as in the case without any colour space conversion at all, with the same overall quality. The use of the XYZ space to compress RGB images, due to the difference between the phosphorus specifications of the CCIR digital TV and the filter specifications of RGB scanner is also discussed, as is the meterameric of filters.