Rammebitmap

Rammebitmap is a compact bitmap data format and memory layout designed for memory-constrained environments such as embedded systems and handheld devices. The name blends RAM and bitmap, signaling its emphasis on minimizing in-RAM footprint while keeping rendering straightforward.

Technical design: A rammebitmap image consists of a small header followed by per-scanline encoded data. The header typically stores width, height, color depth, and a flag indicating whether a palette is used. If a palette is in use, a palette table is stored near the header; otherwise the image uses direct color. Each scanline is encoded with a lightweight run-length and delta encoding scheme, which captures long runs of a single color and small sequential changes. A line-offset table at the beginning or end of the data enables random access to any row without decoding preceding rows.

Data layout: The combination of per-line encoding and a row-offset table allows decoding line by line with limited memory, making rammebitmap suitable for displays with modest RAM. Because encoding is per line, the overall memory footprint can vary with image content and chosen color model.

History and usage: Rammebitmap originated in the Ramme graphics initiative during the mid-2010s as an alternative to uncompressed bitmaps for microcontroller-based tooling. It has appeared in lightweight graphics libraries and hobbyist projects that require predictable RAM usage, supporting both indexed color (8-bit palette) and direct color variants up to 32-bit.

Advantages and limitations: The approach reduces RAM usage for images with large uniform regions and simple gradients, but decoding incurs CPU overhead relative to uncompressed bitmaps and may be inefficient for highly detailed photographs. It is not a universal standard, and implementations vary in options and APIs.

See also: Bitmap, Run-length encoding, Embedded graphics, Palette, True color.