A codec is used to decode or encode a specific media format. WPF Imaging includes a codec for BMP, JPEG, PNG, TIFF, Windows Media Photo, GIF, and ICON image formats. Each of these codecs enable applications to decode and, with the exception of ICON, encode their respective image formats.
BitmapSource is an important class used in the decoding and encoding of images. It is the basic building block of the WPF Imaging pipeline and represents a single, constant set of pixels at a certain size and resolution. A BitmapSource can be an individual frame of a multiple frame image, or it can be the result of a transform performed on a BitmapSource. It is the parent of many of the primary classes used in WPF imaging such as BitmapFrame.
A BitmapFrame is used to store the actual bitmap data of an image format. Many image formats only support a single BitmapFrame, although formats such as GIF and TIFF support multiple frames per image. Frames are used by decoders as input data and are passed to encoders to create image files.
The following example demonstrates how a BitmapFrame is created from a BitmapSource and then added to a TIFF image.
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Dim image5 As BitmapSource = System.Windows.Media.Imaging.BitmapSource.Create(width, height, 96, 96, PixelFormats.Indexed1, BitmapPalettes.WebPalette, pixels, stride)
Dim stream5 As New FileStream("palette.tif", FileMode.Create)
Dim encoder5 As New TiffBitmapEncoder()
encoder5.Frames.Add(BitmapFrame.Create(image5))
encoder5.Save(stream5)
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BitmapSource image5 = BitmapSource.Create(
width,
height,
96,
96,
PixelFormats.Indexed1,
BitmapPalettes.WebPalette,
pixels,
stride);
FileStream stream5 = new FileStream("palette.tif", FileMode.Create);
TiffBitmapEncoder encoder5 = new TiffBitmapEncoder();
encoder5.Frames.Add(BitmapFrame.Create(image5));
encoder5.Save(stream5);
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Image Format Decoding
Image decoding is the translation of an image format to image data that can be used by the system. The image data can then be used to display, process, or encode to a different format. Decoder selection is based on the image format. Codec selection is automatic unless a specific decoder is specified. The examples in the Displaying Images in WPF section demonstrate automatic decoding. Custom format decoders developed using the unmanaged WPF Imaging interfaces and registered with the system automatically participate in decoder selection. This allows custom formats to be displayed automatically in WPF applications.
The following example demonstrates the use of a bitmap decoder to decode a BMP format image.
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' Open a Uri and decode a BMP image
Dim myUri As New Uri("tulipfarm.bmp", UriKind.RelativeOrAbsolute)
Dim decoder2 As New BmpBitmapDecoder(myUri, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default)
Dim bitmapSource2 As BitmapSource = decoder2.Frames(0)
' Draw the Image
Dim myImage2 As New Image()
myImage2.Source = bitmapSource2
myImage2.Stretch = Stretch.None
myImage2.Margin = New Thickness(20)
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// Open a Uri and decode a BMP image
Uri myUri = new Uri("tulipfarm.bmp", UriKind.RelativeOrAbsolute);
BmpBitmapDecoder decoder2 = new BmpBitmapDecoder(myUri, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);
BitmapSource bitmapSource2 = decoder2.Frames[0];
// Draw the Image
Image myImage2 = new Image();
myImage2.Source = bitmapSource2;
myImage2.Stretch = Stretch.None;
myImage2.Margin = new Thickness(20);
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// Open a Uri and decode a BMP image
System::Uri^ myUri = gcnew System::Uri("tulipfarm.bmp", UriKind::RelativeOrAbsolute);
BmpBitmapDecoder^ decoder2 = gcnew BmpBitmapDecoder(myUri, BitmapCreateOptions::PreservePixelFormat, BitmapCacheOption::Default);
BitmapSource^ bitmapSource2 = decoder2->Frames[0];
// Draw the Image
Image^ myImage2 = gcnew Image();
myImage2->Source = bitmapSource2;
myImage2->Stretch = Stretch::None;
myImage2->Margin = System::Windows::Thickness(20);
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Image Format Encoding
Image encoding is the translation of image data to a specific image format. The encoded image data can then be used to create new image files. WPF Imaging provides encoders for each of the image formats described above.
The following example demonstrates the use of an encoder to save a newly created bitmap image.
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Dim stream As New FileStream("new.bmp", FileMode.Create)
Dim encoder As New BmpBitmapEncoder()
Dim myTextBlock As New TextBlock()
myTextBlock.Text = "Codec Author is: " + encoder.CodecInfo.Author.ToString()
encoder.Frames.Add(BitmapFrame.Create(image))
encoder.Save(stream)
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FileStream stream = new FileStream("new.bmp", FileMode.Create);
BmpBitmapEncoder encoder = new BmpBitmapEncoder();
TextBlock myTextBlock = new TextBlock();
myTextBlock.Text = "Codec Author is: " + encoder.CodecInfo.Author.ToString();
encoder.Frames.Add(BitmapFrame.Create(image));
encoder.Save(stream);
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FileStream^ stream = gcnew FileStream("new.bmp", FileMode::Create);
BmpBitmapEncoder^ encoder = gcnew BmpBitmapEncoder();
TextBlock^ myTextBlock = gcnew TextBlock();
myTextBlock->Text = "Codec Author is: " + encoder->CodecInfo->Author->ToString();
encoder->Frames->Add(BitmapFrame::Create(image));
encoder->Save(stream);
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