How to: Encode and Decode a PNG Image

The following examples show how to decode and encode a Portable Network Graphics (PNG) image using the specific PngBitmapDecoder and PngBitmapEncoder objects.

Example

This example demonstrates how to decode a PNG image using a PngBitmapDecoder from a FileStream.

' Open a Stream and decode a PNG image
Dim imageStreamSource As New FileStream("smiley.png", FileMode.Open, FileAccess.Read, FileShare.Read)
Dim decoder As New PngBitmapDecoder(imageStreamSource, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default)
Dim bitmapSource As BitmapSource = decoder.Frames(0)

' Draw the Image
Dim myImage As New Image()
myImage.Source = bitmapSource
myImage.Stretch = Stretch.None
myImage.Margin = New Thickness(20)

// Open a Stream and decode a PNG image
Stream imageStreamSource = new FileStream("smiley.png", FileMode.Open, FileAccess.Read, FileShare.Read);
PngBitmapDecoder decoder = new PngBitmapDecoder(imageStreamSource, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);
BitmapSource bitmapSource = decoder.Frames[0];

// Draw the Image
Image myImage = new Image();
myImage.Source = bitmapSource;
myImage.Stretch = Stretch.None;
myImage.Margin = new Thickness(20);

// Open a Stream and decode a PNG image
Stream^ imageStreamSource = gcnew FileStream("smiley.png", FileMode::Open, FileAccess::Read, FileShare::Read);
PngBitmapDecoder^ decoder = gcnew PngBitmapDecoder(imageStreamSource, BitmapCreateOptions::PreservePixelFormat, BitmapCacheOption::Default);
BitmapSource^ bitmapSource = decoder->Frames[0];

// Draw the Image
Image^ myImage = gcnew Image();
myImage->Source = bitmapSource;
myImage->Stretch = Stretch::None;
myImage->Margin = System::Windows::Thickness(20);

This example demonstrates how to encode a BitmapSource into a PNG image using a PngBitmapEncoder.

Dim width As Integer = 128
Dim height As Integer = 128
Dim stride As Integer = width
Dim pixels(height * stride) As Byte

' Define the image palette
Dim myPalette As BitmapPalette = BitmapPalettes.Halftone256

' Creates a new empty image with the pre-defined palette
Dim image As BitmapSource = System.Windows.Media.Imaging.BitmapSource.Create( _
    width, height, 96, 96, PixelFormats.Indexed8, myPalette, pixels, stride)
Dim stream As New FileStream("new.png", FileMode.Create)
Dim encoder As New PngBitmapEncoder()
Dim myTextBlock As New TextBlock()
myTextBlock.Text = "Codec Author is: " + encoder.CodecInfo.Author.ToString()
encoder.Interlace = PngInterlaceOption.On
encoder.Frames.Add(BitmapFrame.Create(image))
encoder.Save(stream)

            int width = 128;
            int height = 128;
            int stride = width;
            byte[] pixels = new byte[height * stride];

            // Define the image palette
            BitmapPalette myPalette = BitmapPalettes.Halftone256;

            // Creates a new empty image with the pre-defined palette

            BitmapSource image = BitmapSource.Create(
                width,
                height,
                96,
                96,
                PixelFormats.Indexed8,
                myPalette,
                pixels,
                stride);

            FileStream stream = new FileStream("new.png", FileMode.Create);
            PngBitmapEncoder encoder = new PngBitmapEncoder();
            TextBlock myTextBlock = new TextBlock();
            myTextBlock.Text = "Codec Author is: " + encoder.CodecInfo.Author.ToString();
            encoder.Interlace = PngInterlaceOption.On;
            encoder.Frames.Add(BitmapFrame.Create(image));
            encoder.Save(stream);

               int width = 128;
               int height = 128;
               int stride = width;
               array<System::Byte>^ pixels = gcnew array<System::Byte>(height * stride);

               // Define the image palette
               BitmapPalette^ myPalette = BitmapPalettes::Halftone256;

               // Creates a new empty image with the pre-defined palette

               BitmapSource^ image = BitmapSource::Create(width,
                  height,
                  96,
                  96,
                  PixelFormats::Indexed8,
                  myPalette,
                  pixels,
                  stride);

               FileStream^ stream = gcnew FileStream("new.png", FileMode::Create);
               PngBitmapEncoder^ encoder = gcnew PngBitmapEncoder();
               TextBlock^ myTextBlock = gcnew TextBlock();
               myTextBlock->Text = "Codec Author is: " + encoder->CodecInfo->Author->ToString();
               encoder->Interlace = PngInterlaceOption::On;
               encoder->Frames->Add(BitmapFrame::Create(image));
               encoder->Save(stream);

See Also

Concepts

Imaging Overview