Image glossary
ICC profile
Also known as colour profile, color profile, ICC
An ICC profile is a standardised description of how a device or file's colour numbers map to actual perceived colours, allowing the same image to look consistent across screens and printers.
The problem it solves
The numbers in an image file are instructions, not colours. "Red 200, green 30, blue 40" tells a device how hard to drive its red, green and blue elements, and two devices driven identically produce visibly different colours because their elements differ.
An ICC profile closes that gap. It describes, in a standard form defined by the International Color Consortium, how one particular device's or colour space's numbers correspond to absolute colours. Given the profile of the source and the profile of the destination, software can compute the numbers the destination needs to reproduce the same appearance.
Assigning versus converting
These sound similar and do opposite things. Assigning a profile changes the interpretation and leaves the numbers alone: the file now claims a different meaning for the same data, and the colours shift.
Converting changes the numbers to preserve the appearance under a new profile. This is the operation you almost always want, and confusing the two is the most common way people accidentally shift the colour of an entire library.
Why stripping one matters
Metadata stripping is a normal and useful step — it removes EXIF, GPS coordinates and editing history. It also removes the colour profile unless the tool is careful.
For an sRGB image that is harmless, because sRGB is what everything assumes in the absence of a profile. For a wide-gamut image it is not: strip a Display P3 profile and the saturated values are reinterpreted as sRGB, which renders them duller and shifted. Photographs from recent phones are frequently Display P3.
The safe rule is to convert to sRGB before stripping, rather than stripping a profile that was doing work.
Printers have their own profiles, describing a gamut that is smaller than a screen's in some regions and larger in others. This is why saturated blues and greens print duller than they look: those colours are outside what the ink and paper can reproduce, and the conversion has to map them to the nearest achievable value.
Tools that work with this
Related terms
- sRGBsRGB is the default colour space of the web, defining a specific set of red, green and blue primaries and a transfer curve that browsers assume when an image carries no colour profile.
- Display P3Display P3 is a wide-gamut colour space used by modern Apple devices and many recent screens, covering roughly 25% more visible colour than sRGB, particularly in reds and greens.
- EXIFEXIF is metadata embedded in an image file by cameras and phones, recording capture settings, device information, orientation and frequently GPS coordinates.
- Bit depthBit depth is the number of bits used to store each colour channel of a pixel, determining how many distinct levels are available per channel.
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