luminanceonly

Luminanceonly refers to image or video data that contains only luminance information, discarding chrominance (color) data. Luminance, or brightness, is a perceptual measure of how light a pixel appears, and in many color spaces it is represented by a Y component. In digital video and imaging, YCbCr or YUV color spaces separate an image into a luma channel (Y) and two chroma channels (Cb/Cr or U/V), with Y encoding brightness and the chroma channels encoding color.

Producing luminance-only data can be done by converting a color image to grayscale or by extracting the Y channel from a color-encoded signal. Common methods for grayscale conversion use weighted sums of the RGB channels. For linear RGB, Y can be computed as Y = 0.2126 R + 0.7152 G + 0.0722 B. For gamma-encoded sRGB, a widely used approximation is Y' = 0.299 R' + 0.587 G' + 0.114 B'. In video workflows, luminance-only data may be stored as a separate luma plane (as in YCbCr) or used in formats with chroma subsampling where chroma is reduced or omitted, focusing on brightness at full resolution.

Applications and considerations: luminance-only representations reduce data size and emphasize brightness features such as edges and textures, aiding tasks in grayscale imaging, computer vision, and certain display or streaming scenarios. They are unsuitable when color information is required, and in such cases color must be reconstructed or ignored depending on the use case. See also grayscale imaging and luma/chroma concepts in color spaces.