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BMP Format Overview

  • Artikkeli

This topic provides information about the native BMP codec available through the Windows Imaging Component (WIC).

Codec Identity

The following table provides codec identification information.

Component Description
Formal Name(s) Windows Bitmap Format
File Name Extension(s) bmp, dib
MIME type image/bmp
Specification Support BMP Specification v5

 

The following table lists the GUIDs used to identify the native BMP codec components.

Component Friendly Name GUID
Container Format GUID_ContainerFormatBmp 0af1d87e-fcfe-4188-bdeba7906471cbe3
Decoder CLSID_WICBmpDecoder 6b462062-7cbf-400d-9fdb813dd10f2778
Encoder CLSID_WICBmpEncoder 69be8bb4-d66d-47c8-865aed1589433782

 

Encoding

The WIC encoding API are designed to be codec-independent and therefore image encoding for WIC-enabled codecs is essentially the same. For more information about image encoding using the WIC API, see the Encoding Overview.

Encoder Options

WIC-enabled codecs differ at the encoding option level. Encoder options reflect the capabilities of an image encoder and each native codec supports a set of these encoder options. Encoder options can be basic WIC supported options available to all WIC enabled codes (though not necessarily supported) or codec-specific options designed by the image format codec. To manage these encoding options during the encoding process, WIC uses the IPropertyBag2 interface . For more information about using the IPropertyBag2 interface for WIC encoding see the Encoding Overview.

The following table lists the WIC encoder options supported by the native BMP codec.

Property Name VARTYPE Value Range Default Value
EnableV5Header32bppBGRA VT_BOOL VARIANT_TRUE/VARIANT_FALSE VARIANT_FALSE

 

EnableV5Header32bppBGRA

Specifies whether to allow encoding data in the GUID_WICPixelFormat32bppBGRA pixel format. If this option is set to VARIANT_TRUE, the BMP will be written out with a BITMAPV5HEADER header.

The default value is VARIANT_FALSE.

If an encoder option is present in the IPropertyBag2 option list that the codec does not support, it is ignored.

Note for 16-bit and 32-bit Windows BMP files, the BMP codec ignores any alpha channel, as many legacy image files contain invalid data in this extra channel. Starting with Windows 8, 32-bit Windows BMP files written using the BITMAPV5HEADER with valid alpha channel content are read as WICPixelFormat32bppBGRA

Decoding

The WIC decoding API are designed to be codec-independent and image decoding for WIC-enabled codecs is essentially the same. For more information about image decoding, see the Decoding Overview. For more information about using decoded image data, see the Bitmap Sources Overview.