BMP (Windows bitmap, .bmp)

The BMP file format, sometimes called bitmap or DIB file format (for device-independent bitmap), is an image file format used to store bitmap digital images, especially on Microsoft Windows and OS/2 operating systems.
Many graphical user interfaces use bitmaps in their built-in graphics subsystems; for example, the Microsoft Windows and OS/2 platforms' GDI subsystem, where the specific format used is the Windows and OS/2 bitmap file format, usually named with the file extension of .BMP or .DIB.

In uncompressed BMP files, and many other bitmap file formats, image pixels are stored with a color depth of 1, 4, 8, 16, 24, or 32 bits per pixel. Images of 8 bits and fewer can be either grayscale or indexed color. An alpha channel (for transparency) may be stored in a separate file, where it is similar to a grayscale image, or in a fourth channel that converts 24-bit images to 32 bits per pixel.

Uncompressed bitmap files (such as BMP) are typically much larger than compressed (with any of various methods) image file formats for the same image. For example, the 1058×1058 Wikipedia logo, which occupies about 287.65 KB in the PNG format, takes about 3358 KB as a 24-bit BMP file. Uncompressed formats are generally unsuitable for transferring images on the Internet or other slow or capacity-limited media.

The simplicity of the BMP file format, and its widespread familiarity in Windows and elsewhere, as well as the fact that this format is relatively well documented and free of patents, makes it a very common format that image processing programs from many operating systems can read and write.

While most BMP files have a relatively large file size due to lack of any compression, many BMP files can be considerably compressed with lossless data compression algorithms such as ZIP because they contain redundant data.