A colour rendering intent is a method for mapping colours from one colour space to another, particularly when converting colours between devices with different colour gamuts.
There are four standard rendering intents defined by the International Color Consortium (ICC):
Perceptual Intent (Picture):
This intent compresses or expands the full gamut of the source image to fit the destination device’s gamut, preserving the overall colour appearance and relationships between colours. It’s often used for photographs and images with highly saturated colours.
Relative Colorimetric Intent (Proof):
This intent maps colours that fall within both the source and destination gamuts exactly, while clipping out-of-gamut colours to the nearest reproducible colour. It’s suitable for images where luminosity structure is crucial, such as near-neutral and black-and-white images.
Absolute Colorimetric Intent (Match):
Similar to relative colorimetric, but it preserves the white point, making it useful for proofing one device’s output on another.
Saturation Intent (Graphic):
This intent preserves colour saturation, potentially at the expense of hue and lightness. It’s best for business graphics where vivid colours are more important than colour accuracy.
Rendering intents are particularly important when converting colours from a wider-gamut colour space (like ProPhoto RGB) to a smaller-gamut colour space (like a printer’s colour space)2. The choice of rendering intent can significantly affect the final output, especially when dealing with out-of-gamut colours.