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Bitmap Image (.bmp)

The BMP (Bitmap image) is a raster image format that was introduced by Microsoft on the Windows platform. The BMP file is also known as a Device Independent Bitmap (DIB) file, meaning it is independent of display devices and the image file can be viewed without a graphics adapter.

A BMP file with its simplest and the most widely used structure holds 3 bytes of data; 8 bits for each red, green and blue channels. Other data representations like alpha channel and indexed color are also supported, but not commonly used and implemented. Although there are several compression methods and algorithms available, the most common form of BMP format is uncompressed, resulting in large file sizes. This makes BMP image a bad choice for web photographs. It's a good idea to choose WebP for its compression with a fallback to JPEG for its better compatibility.

BMP Specifications

Name Bitmap Image
File Extension(s) .bmp
Category Raster Images
Use For Windows computers and general software graphic platforms, 2D applications. However, it is not widely used and recommended nowadays, because of better alternatives.
Developer Microsoft Corporation
MIME Type(s) image/bmp
License Covered by the Microsoft Open Specification Promise; while Microsoft holds patents against BMP, they have published a promise not to assert its patent rights as long as specific conditions are met. This is not the same as a license, however. BMP is included under the Windows Metafile Format (.wmf).
File Sample(s) N/A
Compression None, RLE (Run-Length Encoding), JPEG and PNG.
Max Dimensions Either 32,767×32,767 or 2,147,483,647×2,147,483,647 pixels, depending on the format version
Color Modes
Mode Bits Description
Greyscale 1 Each bit represents a single pixel, which can be either black or white.
True color 8 and 16 Each pixel is represented by three values representing the red, green, and blue color components; each is D bits.
Indexed color 2, 4, and 8 Each pixel is represented by a value which is one 2, 4, or 8 bits, serving as an index into the color table.
Greyscale with alpha N/A BMP has no distinct grayscale format.
True color with alpha 8 and 16 Each pixel is represented by four values representing the red, green, blue, and alpha color components; each is D bits.
Animation No
Transparency Yes
Interlacing No
Metadata No
Layers No
Multipage No
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