GIMP Dimage color plugin

The GIMP Dimage color plugin converts JPEG/TIFF files produced by the Minolta DiMAGE 5/7 digital camera into sRGB colorspace. The process consists in:

  1. Applying the inverted DiMAGE gamma curve to input RGB values;
  2. Converting the linearized RGB values into sRGB (Gamut transformation);
  3. Applying the contrast correction ("iTRC") curve *;
  4. Applying the sRGB gamma curve.

The highlighted area in Fig. 1 corresponds to the colors that the DiMAGE can capture. The area inside the black triangle corresponds to the colors displayable in sRGB colorspace.

* The contrast correction curve can be found in ICC profiles provided by Minolta with the Dimage Viewer Utility. It correspond to a tag ("iTRC") which is not part of the ICC specifications. This explains why softwares like the lcms library or Photoshop can't properly handle those profiles.


DiMAGE and sRGB color gamuts
Fig. 1: DiMAGE and sRGB color gamuts
Gamma and iTRC curves
Fig. 2: Gamma and iTRC curves

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Laurent Houdard -