IccProfile
The part of an ICC profile a document reader actually needs: how the colours of a grey, RGB or CMYK profile map to sRGB.
An ICC profile says how a file's numbers map to real colour. Ignoring it is what makes a photo tagged AdobeRGB look flat when it is drawn as if it were sRGB. A matrix/TRC profile has tone curves and a colorant matrix, and converts through XYZ. A lookup-table profile, which most CMYK press profiles are, converts through the table of the rendering intent with black point compensation, as MuPDF does through Little CMS (#200, #201). parse gives the relative colorimetric transform, and forRendering the transform of any other intent.
Properties
1 for grey, 3 for RGB, 4 for CMYK.
True when this profile IS sRGB (or near enough), so converting through it would only add rounding. Most PDFs tag their colours "sRGB IEC61966-2.1", and for those the honest transform is no transform: the round trip through XYZ costs about a level of 0..255 and buys nothing.
Functions
Convert components (0..1 per channel) to sRGB.