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PNG Format Overview

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

Codec Identity

The following table provides codec identification information.

Component Description
Formal Name(s) Portable Network Graphics (PNG)
File Name Extension(s) png
MIME type image/png
Specification Support PNG Specification 1.2

 

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

Component Friendly Name GUID
Container Format GUID_ContainerFormatPng 1b7cfaf4-713f-473c-bbcd6137425faeaf
Decoder CLSID_WICPngDecoder 389ea17b-5078-4cde-b6ef25c15175c751
Encoder CLSID_WICPngEncoder 27949969-876a-41d7-9447568f6a35a4dc

 

Windows 8 and later

Starting with Windows 8 WIC provides an additional PNG decoder

Encoding

The WIC encoding API are designed to be codec-independent and 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 PNG codec uses basic WIC encoder options. The following table lists the WIC encoder options supported by the native PNG codec.

Property Name VARTYPE Value Range Default Value
InterlaceOption VT_BOOL TRUE/FALSE FALSE
FilterOption VT_UI1 WICPngFilterOption WICPngFilterUnspecified

 

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

InterlaceOption

Specifies whether to encode the image data as interlaced.

The default value is FALSE.

FilterOption

Specifies the filter option to use for image compression.

The default value is WICPngFilterUnspecified.

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.

The native PNG codec also supports the IWICBitmapSourceTransform on frame decoding adding advanced options for decoding an image stream. For more information about these advanced options, see the Bitmap Sources Overview.