Convert BMP to PPM / PNM

The BMP (Bitmap) format, formally known as the Device Independent Bitmap (DIB) file format, is a raster graphics standard developed by Microsoft for the Windows operating system. The file structure consists of a file header (BITMAPFILEHEADER), an information header (typically BITMAPINFOHEADER), a color table, and the pixel array. Data is stored as a grid of pixels with color depths ranging from 1-bit to 32-bit, typically uncompressed, though the format supports lossless Run-Length Encoding (RLE4 or RLE8) and Huffman 1D compression for specific bit depths.

Due to its simplicity and documentation as a core Windows standard, BMP files possess near-universal compatibility. They can be opened natively by virtually all image viewers and web browsers across Windows, macOS, and Linux without additional software. Standard utilities include Microsoft Paint, Apple Preview, and Windows Photos. For advanced manipulation, pixel-based editors like Adobe Photoshop and CorelDRAW are recommended, though the format is rarely used for complex editing due to its large file size.

The Portable Pixel Map (PPM) format is a lowest-common-denominator color image format developed by Jef Poskanzer as part of the Netpbm project. It stores pixels as uncompressed RGB triplets (Red, Green, Blue) in either a plain ASCII text format (P3 header) or a more efficient binary format (P6 header). The file structure is extremely minimal, consisting of a magic number identifier, dimensions (width and height), maximum color value, and the pixel data itself, making it easily parsable by simple scripts but inefficient for storage compared to compressed formats like JPEG or PNG.

Native support for PPM files is absent in standard Windows or macOS photo viewers. Users typically require specialized image manipulation software to view or convert these files. GIMP (GNU Image Manipulation Program) and IrfanView are the primary tools for opening PPM files on desktop environments. On Linux systems, the Netpbm toolkit and ImageMagick suite provide command-line utilities for processing and converting PPM data.