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How to: Load an Image as a Thumbnail

The following examples show how to load an Image as a thumbnail to conserve application memory.

The following example sets the DecodePixelWidth property of a BitmapImage in Extensible Application Markup Language (XAML) to reduce the memory required to load the image.

<!-- Simple image rendering. However, rendering an image this way may not
     result in the best use of application memory. See markup below which
     creates the same end result but using less memory. -->
<Image Width="200" 
Source="C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Water Lilies.jpg"/>

<Image Width="200">
  <Image.Source>
    <!-- To save significant application memory, set the DecodePixelWidth or  
     DecodePixelHeight of the BitmapImage value of the image source to the desired 
     height and width of the rendered image. If you don't do this, the application will 
     cache the image as though it were rendered as its normal size rather then just 
     the size that is displayed. -->
    <!-- Note: In order to preserve aspect ratio, only set either DecodePixelWidth
         or DecodePixelHeight but not both. -->
    <BitmapImage DecodePixelWidth="200"  
     UriSource="C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Water Lilies.jpg" />
  </Image.Source>
</Image>

The following example sets the DecodePixelWidth property of a BitmapImage in code to reduce the memory required to load the image.

' Create Image Element 
Dim myImage As New Image()
myImage.Width = 200

' Create source 
Dim myBitmapImage As New BitmapImage()

' BitmapImage.UriSource must be in a BeginInit/EndInit block
myBitmapImage.BeginInit()
myBitmapImage.UriSource = New Uri("C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Water Lilies.jpg")

' To save significant application memory, set the DecodePixelWidth or   
' DecodePixelHeight of the BitmapImage value of the image source to the desired  
' height or width of the rendered image. If you don't do this, the application will  
' cache the image as though it were rendered as its normal size rather then just  
' the size that is displayed. 
' Note: In order to preserve aspect ratio, set DecodePixelWidth 
' or DecodePixelHeight but not both.
myBitmapImage.DecodePixelWidth = 200
myBitmapImage.EndInit()
'set image source
myImage.Source = myBitmapImage
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