cmap

Cmap, often written as CMap or cmap, is a term used in several related but distinct areas of computing to denote a mapping between two sets of values. The most common senses are character mapping in typography and color mapping in visualization, with the term also appearing as a variable name in software libraries.

In typography and digital fonts, a CMap is a character map that defines how character codes map to glyphs or to Unicode values. This is especially important for multi-byte encodings used by East Asian fonts and CID-keyed font architectures. In PDFs and PostScript workflows, CMaps describe the mapping spaces and facilitate correct rendering of text by linking input byte sequences to the appropriate glyphs or Unicode code points. Standard and custom CMaps enable support for various encodings and font technologies.

In imaging and data visualization, cmap commonly refers to a colormap, a mapping from scalar data values to colors. Colormaps are used to colorize grayscale or single-channel images and data sets for human interpretation. Common types include sequential maps for ordered data, diverging maps for deviations from a midpoint, and qualitative maps for categories. Perceptual considerations and accessibility, such as ensuring distinguishability for colorblind viewers, influence colormap design and selection.

In software and plotting libraries, cmap is often a parameter name or variable that specifies which color map to apply. Users may select a predefined colormap or supply a custom palette to control the visual appearance of plots, heatmaps, and other graphical outputs.

See also: character encoding, font technologies, PDF and PostScript CMaps, color maps, data visualization.