Curve (tonality)

In image editing, a curve is a remapping of image tonality, specified as a function from input level to output level, used as a way to emphasize colours or other elements in a picture.

Applying a curve to all channels typically changes the brightness in part of the spectrum.

Light parts of a picture can be easily made lighter and dark parts darker to increase contrast.

[3] Applying a curve to individual channels can be used to stress a colour.

This is particularly efficient in the Lab colour space due to the separation of luminance and chromaticity,[4] but it can also be used in RGB, CMYK or whatever other colour models the software supports.