BMP
BMP is a family of simple raster graphics image file formats designed to store bitmap digital images independently of a display device. BMP was originally and is primarily used on Microsoft Windows and OS/2 operating systems. The format is sometimes known as Device-Independent Bitmap (DIB), since, when loaded into memory using Windows software, the image is held as a DIB structure.
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Identification
No MIME type has been officially registered. Strings found in practice are: image/bmp; image/x-bmp; image/x-ms-bmp
The standard file extension is .bmp. Reportedly, .dib and .rle have occasionally been used.
BMP files start with bytes 'B' 'M' ?? ?? 00 00 00 00.
Well-known versions
Unless otherwise indicated, BMP files all use a common 14-byte file header, named BITMAPFILEHEADER. Following that is the "Info header", which begins with a 4-byte integer indicating its size. The Info header size (mostly) reveals the version of BMP that the file uses.
Windows BMP v2
- Info header size: 12
- Info header name: BITMAPCOREHEADER or OS21XBITMAPHEADER
- PRONOM: fmt/115
Also known as OS/2 BMP 1.0.
Windows BMP v3
- Info header size: 40
- Info header name: BITMAPINFOHEADER
- PRONOM: fmt/116 (1, 4, 8, 24 bits/pixel), fmt/117 (16, 32 bits/pixel)
This is by far the most widely used version of BMP.
When 16 or 32 bits/pixel is supported, the format may be known as "BMP 3.0 NT".
Note: It's possible that some OS/2 BMP 2.0 files also have a header size of 40.
Windows BMP v4
- Info header size: 108
- Info header name: BITMAPV4HEADER
- PRONOM: fmt/118
Windows BMP v5
- Info header size: 124
- Info header name: BITMAPV5HEADER
- PRONOM: fmt/119
Other versions
Windows BMP v1
- PRONOM: fmt/114
Based on limited information, this format does not use the usual 14-byte header. The file extension may be .bmp or .ddb.
OS/2 BMP 2.0
- Info header size: 16, 40, 48, or 64 (?)
- Info header name: BITMAPCOREHEADER2 or OS22XBITMAPHEADER
- PRONOM: x-fmt/270
See OS/2 BMP.
BITMAPV2INFOHEADER
- Info header size: 52
- Info header name: BITMAPV2INFOHEADER
No details known.
BITMAPV3INFOHEADER
- Info header size: 56
- Info header name: BITMAPV3INFOHEADER
No details known.
Specifications
Sample images
References
- BMP (file format): Wikipedia
- Bitmap Image File (BMP), Version 5, from Library of Congress resource on Sustainability of Digital Formats
- Microsoft Windows Bitmap File Format Summary From Encyclopedia of Graphics File Formats at FileFormat.Info (1996)
