luminancemap

A luminance map is a representation of brightness values across a two-dimensional scene, produced as a single-channel image in which each pixel corresponds to the perceived luminance at that location. It is commonly used in digital imaging pipelines to separate brightness information from color information and to support perceptual analysis, enhancement, and processing tasks.

In standard color imagery, luminance can be derived from the red, green, and blue channels through a weighted sum. A common formula for computed luminance is Y = 0.2126 R + 0.7152 G + 0.0722 B, corresponding to the luminance component in the Rec. 709 color space. Alternative sources for luminance include the Y channel of color spaces such as YUV or YCbCr, or the linear luminance values obtained after gamma-corrected or tone-mapped processing, depending on the application.

Luminance maps have a wide range of applications. They are used in tone mapping to compress high dynamic range scenes for display, in exposure fusion and contrast enhancement, and in image and video segmentation or object detection where brightness is a distinguishing feature. They also support visualization, perceptual studies, and analytics where color information is either irrelevant or distracting.

Formats and variations include grayscale images, heatmaps, or perceptual maps that emphasize brightness in different scales. Generation may involve linear or nonlinear transformations, gamma correction, dynamic range adjustments, or conversion from HDR radiance data. Temporal luminance consistency is a consideration in video to avoid flicker or abrupt brightness changes.

Related concepts include luminance versus luminance contrast, chrominance, and luminance normalization. Understanding luminance maps aids in objective brightness analysis and in perceptually informed image processing workflows.