BMP File Format - Device-independent Bitmaps and The BMP File Format

Device-independent Bitmaps and The BMP File Format

Microsoft has defined a particular representation of color bitmaps of different color depths, as an aid to exchanging bitmaps between devices and applications with a variety of internal representations. They called these device-independent bitmaps or DIBs, and the file format for them is called DIB file format or BMP image file format. According to Microsoft support:

A device-independent bitmap (DIB) is a format used to define device-independent bitmaps in various color resolutions. The main purpose of DIBs is to allow bitmaps to be moved from one device to another (hence, the device-independent part of the name). A DIB is an external format, in contrast to a device-dependent bitmap, which appears in the system as a bitmap object (created by an application...). A DIB is normally transported in metafiles (usually using the StretchDIBits function), BMP files, and the Clipboard (CF_DIB data format).

The following sections discuss the data stored in the BMP file or DIB in detail. This is the standard BMP file format. Some applications create bitmap image files which are not compliant with the current Microsoft documentation. Also, not all fields are used; a value of 0 will be found in these unused fields.