PGM to PCX Converter

PCX (PiCture eXchange) is a raster image format created by ZSoft Corporation in 1985 as the native format of their PC Paintbrush application, one of the first painting programs for IBM PC compatibles. The format uses a simple run-length encoding (RLE) compression scheme that works by replacing consecutive identical pixel values with a count-value pair, achieving modest compression on images with large areas of uniform color. A PCX file consists of a 128-byte header (specifying dimensions, color depth, palette information, DPI, and encoding method), the RLE-compressed pixel data organized in scan-line order, and an optional 256-color palette appended after the image data. The format evolved through several versions supporting increasing color depths: 1-bit monochrome, 4-bit (16 colors), 8-bit (256 colors), and 24-bit true color using multiple color planes. PCX became one of the most popular image formats during the DOS era, widely supported by paint programs, word processors, desktop publishers, and early games throughout the late 1980s and early 1990s. One advantage was broad DOS-era software compatibility — PCX served as a practical interchange format when competing programs used proprietary raster formats. The simplicity of RLE decoding is another strength, requiring minimal CPU and memory resources ideal for the hardware of that period. While PNG, JPEG, and other modern formats have replaced PCX in contemporary use, the format remains encountered in legacy archives and retro computing contexts.