ICC Profile Creator
Introduction
The ICC Profile Creator allows you to generate your own ICC profiles. You can use standard presets as well as custom values.
RawTherapee can generate output, screen or custom working profiles using the XYZ matrix generated for Custom profiles
You cannot adjust all the parameters of an ICC profile with this tool, e.g. the A2B or B2A tags, but you can adjust those that are important for a photographer i.e. the primary colors, the tone reproduction curve, and the white point (illuminant).
You can generate profiles in accordance with ICC versions 2 and 4, and in both cases you can use custom primaries and modify the illuminant as well as the tone reproduction curve (TRC).
The code and the basic principles are similar to those used for Abstract profiles
Using the profile generator
To access the Profile Generator dialog box, click on the button next to the Preferences and Help icons (File:Toolbar icc-creator.jpg) at the far left or top right of the RawTherapee window.
To make the profiles subsequently available for use in RawTherapee, save them in the standard color profile directory of your operating system as defined in the Preferences > Color Management tab.
The primary colors
The three primary colors - Red, Green, Blue - are additive and form the basis of all other colors. In the ICC profile generator, you specify the location of the primary colors on the 1931 CIE xy chromaticity diagram using the xy coordinates.
The tone reproduction curve (TRC)
The TRC is essentially a curve that transforms the initial or input values of the image into values that will be recorded in the output image. We can modify 2 parameters:
- Gamma,
- Slope.
You can choose predefined values such as 'standard g 2.2', 'sRGB g=2.4 s=12.92' or build a custom TRC. In the case of a custom TRC, the curve will consist of a linear part and a parabolic part with a seamless connection between the two.
You can see other uses of the TRC in Abstract profiles > TRC_-_Tone_Response_Curve.
Illuminant
The illuminant is used to derive the white-point reference for color profiles. The white point, which is identified by its temperature and a symbol (D50, StdA 2856K, Fluorescent F11, etc.) is represented using either XYZ or xyY data calculated as follows: X,Z (Y= 1) = Sum of the matrix product from 350nm to 830nm [Observer 2° x or z][Illuminant I]/ Sum of the matrix product from 350nm to 830nm [Observer 2° y][Illuminant I].
Although the colors are usually encoded using one of the standard D50, D60 or D65 illuminants, you can specify a different illuminant in the drop-down list. In this case, the profile generator will add the necessary chromaticity adaptation to convert the colors to the selected illuminant.
For further information on illuminants and Abstract Profiles see: Illuminant - Abstract profile.