CroppedBitmap.Source Property

<Page.Resources>
   <!-- Define some image resources, for use as the image element source. -->
   <BitmapImage x:Key="masterImage" UriSource="/sampleImages/gecko.jpg" />
   <CroppedBitmap x:Key="croppedImage" 
      Source="{StaticResource masterImage}" SourceRect="30 20 105 50"/>
</Page.Resources>

<!-- Use the cropped image resource as the images source -->
<Image Width="200" Source="{StaticResource croppedImage}" 
   Margin="5" Grid.Column="0" Grid.Row="1" />

// Create an Image element.
Image croppedImage = new Image();
croppedImage.Width = 200;
croppedImage.Margin = new Thickness(5);

// Create a CroppedBitmap based off of a xaml defined resource.
CroppedBitmap cb = new CroppedBitmap(     
   (BitmapSource)this.Resources["masterImage"],
   new Int32Rect(30, 20, 105, 50));       //select region rect
croppedImage.Source = cb;                 //set image source to cropped

<!-- Chain a cropped bitmap off a previosly defined cropped image -->
<Image Width="200" Grid.Column="0" Grid.Row="3" Margin="5">
   <Image.Source>
      <CroppedBitmap Source="{StaticResource croppedImage}" 
         SourceRect="30 0 75 50"/>
   </Image.Source>
</Image>

// Create an Image element.
Image chainImage = new Image();
chainImage.Width = 200;
chainImage.Margin = new Thickness(5);

// Create the cropped image based on previous CroppedBitmap.
CroppedBitmap chained = new CroppedBitmap(cb,
   new Int32Rect(30, 0, (int)cb.Width-30, (int)cb.Height)); 
// Set the image's source.
chainImage.Source = chained;