Bitmap Image (MIME: image/bmp) is an uncompressed raster image format originally developed by Microsoft and IBM for Windows operating systems, known for its simplicity but very large file sizes.
History and Development
BMP (Bitmap Image File) was introduced with Windows 1.0 in 1985 and evolved through Windows 3.0 (1990), which added support for 24-bit color and RLE compression. While largely replaced by JPEG and PNG for everyday use, BMP remains relevant in embedded systems, legacy software, and situations requiring uncompressed pixel data.
Technical Specifications
- Compression: Typically uncompressed; optional RLE compression
- Color depth: 1-bit to 32-bit (including alpha)
- Transparency: 32-bit BMP supports alpha channel
- Max resolution: Limited by file size (no formal pixel limit)
- Metadata: Minimal header information only
Common Use Cases
BMP is used in Windows system graphics, legacy applications, embedded systems, image processing pipelines (as intermediate format), and situations where uncompressed pixel data is required. Scanners and some medical imaging systems output BMP.
BMP vs Similar Formats
- BMP vs PNG: PNG provides lossless compression (5-10x smaller files) with transparency. PNG is preferred for virtually all use cases.
- BMP vs TIFF: TIFF offers more features (layers, CMYK) and optional compression. BMP is simpler but less versatile.
How to Open and Edit
BMP opens natively on Windows (Photos, Paint) and macOS (Preview). GIMP, Photoshop, and most image editors support BMP. For web use, convert BMP to PNG or WebP to dramatically reduce file size.
Frequently Asked Questions
Why are BMP files so large?
BMP stores raw pixel data without compression. A 1920×1080 24-bit BMP is ~6 MB, while the same image as JPEG might be 200 KB.
Should I use BMP for anything?
Only in specific cases: legacy software compatibility, embedded systems, or image processing pipelines that require uncompressed data. For everything else, use PNG or WebP.