Color Transformer 2 — version 2.03  (11/3/2023)

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Author: Maria E. Barilla (perezm at
Digital Systems & Vision Processing Group
Electronic, Electrical and Computer Engineering School
The University of Birmingham, UK
History: 2007/11/08: First version
2012/02/19: Fixed bug in HSI transform
2013/02/14: Fixed bug in L*a*b* transform (by WAHeeschen)
2014/01/25: Added more RGB color spaces, YCbCr and CMYK output spaces
2014/07/18: Corrected the label for LCHLab from LSHLab
2014/08/3: Corrected the hue calculations for LCHLuv, LSHLuv, LCHLab; added HCY and LSHLab color spaces.
2023/11/3: Ensured that the correct RGB color image is used in batch mode.
Installation: Download Color_Transformer_2.class to the plugins folder, or subfolder, restart ImageJ, and there will be new “Color Transformer 2” command in the Plugins menu or submenu.
Description: This plugin converts an RGB color image into a color space represented by a stack.
It is designed for accurate conversion and measurement of 8- or 16-bit images from various RGB color spaces.
It includes sRGB, Adobe RGB, ProPhoto RGB, and eciRGB v2 input color spaces, and can be customized with the addition of more.
The XYZ, Yxy, YUV, YIQ, YCbCr, Luv, Lab, AC1C2, I1I2I3, Yuv, YQ1Q2, HSI, HSV, HSL, HCY, LCHLuv, LSHLuv, LCHLab, LSHLab, and CMYK output color spaces are supported.

This plugin does not work on stacks, but the Color Transform 2 Stack macro runs it on all the images in an RGB stack and creates a second stack containing the output images.  Requires at least version 2.02 of Color Transformer 2, above.

Additional macros that use Color Transformer 2:

BTDZS Zone Ruler measures the mean L* values and signal-to-noise ratios of an exposure series, and stitches the images into a zone ruler.  Updated 2/22/2014, it now displays a simple plot of the values.  See a screenshot at Nikon D800E Calibration with RawTherapee.

Lab composite generates a composite image whose channels have ranges:  L* 0-100, a* and b* -128-127.

Description: First time anywhere:  code for calculating LSHLab, proposed by Eva Lübbe in Experimental Evidence of the Formula of Saturation, Journal of Physical Science and Application 3 (2) (2013) 79-81.  Included in Color Transformer 2 for comparison; LCHLab is probably more useful for photo editing.

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