What is BMP?BMP is an image file format created by Microsoft. Also called ‘bitmap’ or DIB (device independent bitmap) file format, it is used to store bitmap digital images mainly in the Microsoft Windows environment. The other platforms that support the BMP file format are OS/2 and MS-DOS.
BMP was designed to contain bitmaps of different color resolutions so they could easily be exchanged between different internal devices. Hence the name device independent bitmaps, or DIB. As opposed to a device-dependent bitmap, the DIB/BMP is an external bitmap where it is transported in metafiles.
A BMP file consists of four blocks, or sections, of data. The first is the file header which contains the general information about the BMP file; the second block is the bitmap header containing detailed information about the bitmap image; the third is the color palette with definitions of the colors in the indexed color bitmaps; and the fourth and the last block contains the actual image, pixel by pixel.
Out of these four blocks, the color palette is the only one that can vary in size depending on the depth of the bitmap data. The various depths available are 1 (mono), 4 (indexed), 8 (indexed), 16 (5:6:5 RGB), 16 (5:5:5:1 RGB), 16 (5:5:5:1 RGBA), 24 (true color), 32 (true color RGB), and 32 (true color RGBA). Naturally, bitmap images saved at higher number bits per pixel are greater quality images than those saved at lower number bit images, but the file size will be larger.
The integers in a BMP file are stored in little endian format, another name for the Intel format. This is because the BMP format was actually created for computers with Intel processors.
With the file extension of ‘.bmp’ or ‘.dib’, the BMP file format is very popular because of its usability and wide software support. Its best use is in sending someone an image about whom you are not sure which program he/she uses.
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