[WIP] Color conversion with ICC profiles

[ABildstein]

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Description

As the title says, this adds methods for converting colors with an ICC profile.

Architecturally, the idea is that the profile is checked once for available and appropriate conversion methods and a then a delegate is stored that only takes the color values to convert and returns the calculated values. The possible performance penalty for using a delegate is far smaller than searching through the profile for every conversion. I'm open for other suggestions though.

There are classes to convert from the profile connection space (=PCS, can be XYZ or Lab) to the data space (RGB, CMYK, etc.) and vice versa. There are also classes to convert from PCS to PCS and Data to Data but they are only used for special profiles and are not important for us now but I still added them for completeness sake.

A challenge here is writing tests for this because of the complexity of the calculations and the big amount of different possible conversion paths. This is a rough list of the paths that exist:

• "A to B" and "B to A" tags
  • IccLut8TagDataEntry
    • Input IccLut[], Clut, Output IccLut[]
    • Matrix(3x3), Input IccLut[], IccClut, Output IccLut[]
  • IccLut16TagDataEntry
    • Input IccLut[], IccClut, Output IccLut[]
    • Matrix(3x3), Input IccLut[], IccClut, Output IccLut[]
  • IccLutAToBTagDataEntry/IccLutBToATagDataEntry (Curve types can either be IccCurveTagDataEntry or IccParametricCurveTagDataEntry (which has several curve subtypes))
    • CurveA[], Clut, CurveM[], Matrix(3x1), Matrix(3x3), CurveB[]
    • CurveA[], Clut, CurveB[]
    • CurveM[], Matrix(3x1), Matrix(3x3), CurveB[]
    • CurveB[]
• "D to B" tags
  • IccMultiProcessElementsTagDataEntry that contains an array of any of those types in any order:
    • IccCurveSetProcessElement
      • IccOneDimensionalCurve[] where each curve can have several curve subtypes
    • IccMatrixProcessElement
      • Matrix(Nr. of input Channels by Nr. of output Channels), Matrix(Nr. of output channels by 1)
    • IccClutProcessElement
      • IccClut
• Color Trc
  • Matrix(3x3), one curve for R, G and B each (Curve types can either be IccCurveTagDataEntry or IccParametricCurveTagDataEntry (which has several curve subtypes))
• Gray Trc
  • Curve (Curve type can either be IccCurveTagDataEntry or IccParametricCurveTagDataEntry (which has several curve subtypes))

The three main approaches in that list are

• A to B/B to A: using a combination of lookup tables, matrices and curves
• D to B: using a chain of multi process elements (curves, matrices or lookup)
• Trc: using curves (and matrices for color but not for gray)

The most used approaches are Color Trc for RGB profiles and LutAToB/LutBToA for CMYK profiles.

Todo list:

• Integrate with the rest of the project
• Write tests that cover all conversion paths
• Review architecture
• Improve speed and accuracy of the calculations

Help and suggestions are very welcome.