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Colour Resources

There are many conflicting definitions of the Hue, Saturation and Brightness colour space. In the following documents, we attempt to clear up some of the confusion related to this subject:

  • The latest version is this 2008 Pattern Recognition Letters PaperSpringer-Verlag).
  • A slightly older version of the work is presented in this SCIA 2003 paperSpringer-Verlag).
  • A much more detailed description is available in this PRIP technical report (with Jean Serra), which expands the material in chapter 4 of my thesis. A summary of this work is given in this paper presented at the DAGM 2003Springer-Verlag). Note that there is an error in equation (6) of the printed version of the latter paper, which is corrected in the online version.
  • For those of you wondering what the colour gamuts of the proposed spaces look like, the following animations are available (in AVI format). They present a slice through the achromatic axis of the spaces, which rotates through 360°. The achromatic axis is in the middle of the image, and the hue values (in degrees) to the left and right of it are indicated.
    • L1 norm space: Brightness is the mean of R, G and B, L1 chroma and (non-trigonometric) hue are used. View
    • max-min semi-norm space: Brightness is the mean of R, G and B, saturation is the max-min semi-norm and hue is the exact trigonometric version. View
    • max-min semi-norm space: The luminance weightings are used for brightness, while the other two coordinates are the same used in the previous animation. View


  • Two Matlab functions which perform the forward and backward conversions between the RGB space and the suggested 3D polar coordinate IHLS (Improved Hue, Luminance and Saturation) colour space are here: (Thanks to Thomas Knudsen for the code optimisations).
  • A Python version of the above functions, written by Alexander Schindler:
colour_resources.txt · Last modified: 2014/07/22 19:09 by admin
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