Pixmap

Pixmaps are a basic image representation in computer graphics, defined as a grid of picture elements or pixels. They are stored in memory as a raster image and can be drawn to a display, painted onto another image, or used as textures in rendering pipelines. A pixmap typically records color for each pixel, and may include an alpha channel for transparency. Color depth can vary, from low bit depths to 24-bit RGB or 32-bit RGBA, depending on the system and API.

In the X Window System and related UI toolkits, a pixmap often refers to an off-screen drawable resource that resides on the server. Such a pixmap can be created, manipulated, and later copied into on-screen windows; it may be used to accelerate composition and reduce redraws. Some frameworks distinguish between pixmaps and images: pixmaps emphasize on-screen or off-screen rendering efficiency, while image objects emphasize portability and storage formats.

Common uses include off-screen buffering for smooth scrolling, sprites in games, icons, button states, and textures for rendering. Because a pixmap represents raw pixel data, its memory footprint grows with width, height, and bytes-per-pixel, so applications choose appropriate color formats and alignment. Many APIs provide both a Pixmap type and an Image type; the latter is typically source data and may be converted to a Pixmap for display performance.

Related terms include bitmaps (often monochrome or uncompressed pixel grids that may be device-dependent), raster images, and toolkit-specific classes such as Qt's QPixmap or GDK's pixbuf, which adapt pixmap data to their rendering pipelines.