Friday, February 15, 2019 [Tweets] [Favorites]

Color Spaces

Bartosz Ciechanowski:

A color space can specify how the numeric values of the red, green, and blue components map to intensity of the corresponding light source. In other words, the position of a slider may not be equal to intensity of the light the slider controls.

[…]

This may seem all like a pointless transformation, but there is a good reason for doing all this nonlinear mapping. The human eye is not a simple detector of the power of the incoming light – its response is nonlinear. A two-fold increase in emitted number of photons per second will not be perceived as twice as bright light.

If we were to encode the colors using floating point numbers the need for a nonlinear encoding function would be diminished. However, the numeric values of color are often encoded using the familiar 8 bits per component, e.g. in the most common configurations of JPEG and PNG files. Using a nonlinear tone response curve, or TRC for short, lets us maintain more or less perceptual uniformity and use the chunky, quantized range to keep the detail in the darker parts.

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