Color management
This article introduces color management concepts and explains how color conversion works in Colors, including why results may differ from professional tools such as Photoshop.
Conversion
Colors performs conversions between color models using common linear remapping algorithms, which are straightforward mathematical formulas that map values directly from one model to another.
Color conversion is a complex topic that often causes confusion and can result in discrepancies between different applications.
Professional graphics software such as Photoshop takes a different approach, using ICC color profiles to define how colors are interpreted for specific devices and conditions, routing conversions through an intermediate profile connection space (PCS). The active color profiles can be reviewed and adjusted in Photoshop's Color Settings.
A conversion using linear remapping:
RGB -> [linear remapping algorithm] -> CMYK
A conversion using color profiles:
RGB -> [sRGB / IEC 61966-2-1:1999] -> LAB -> [Coated FOGRA39 / ISO 12647-2:2004] -> CMYK
This means that colors converted in Colors may not match those produced by Photoshop or other profile-aware software, particularly for CMYK output where color space characteristics have a significant impact.
Definitions
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Color management § — the controlled conversion between color representations across different devices and media, such as monitors, cameras, and printers.
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Color model § — an abstract mathematical system for describing colors as a set of numeric components, such as RGB (three components) or CMYK (four components).
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Color space § — a color model combined with precise rules for interpreting its values, producing a defined and reproducible set of colors. Examples include sRGB and Adobe RGB.
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Color profile (ICC profile) § — a standardized data set describing the color characteristics of a device or color space, used to map colors accurately when converting between different color spaces.