rgb51

rgb51 is a compact color representation occasionally used in constrained graphics systems and retro-inspired display technologies. The designation suggests a specific allocation of bits among the color channels, typically meaning red uses 5 bits, while green and blue each use 1 bit, totaling seven meaningful bits per pixel. Because there is no universal standard for rgb51, implementations vary across devices and software.

In common practice, the seven significant bits are packed within a single byte, leaving one bit unused. A typical layout places the most significant five bits to red, followed by one green bit and one blue bit. For example, a byte might be organized as [R4 R3 R2 R1 R0 G B x], with x representing an unused bit. Some variants may reposition the green and blue bits or use multi-byte representations for alignment, depending on hardware constraints.

Color interpretation and conversion to higher color depths: red values range from 0 to 31, while green and blue are either 0 or 1. To convert to an 8-bit-per-channel color, red can be scaled by 255/31, yielding red8 ≈ (red5 × 255) / 31. Green and blue map to either 0 or 255. In some pipelines, dithering is used to mitigate banding artifacts when displaying gradients.

Applications and trade-offs: rgb51 trades color resolution for reduced memory usage and bandwidth, making it suitable for simple LED panels, microcontroller graphics, or early-generation embedded displays. It is generally not used for modern high-fidelity color work but serves as a practical option in tightly constrained environments.

See also: rgb565, rgb555, rgb888, color depth, indexed color.