Create a Thumbnail
The BitmapImage class is used to create a
thumbnail in WPF. The DecodePixelWidth and DecodePixelHeight properties are used
to set the size of the bitmap from an image and this bitmap can be displayed in
an Image control.
The BitmapImage element in XAML represents a
Bitmap Image control at design-time. The following code snippet creates a
BitmapImage element and set its DecodePixelWidth and DecodePixelHeight
attributes.
<Image
Width="120"
Height="120"
HorizontalAlignment="Center">
<Image.Source>
<BitmapImage
DecodePixelWidth="100"
DecodePixelHeight="100"
UriSource="Garden.jpg" />
</Image.Source>
</Image>
Listing 40 shows a Window with two Image
controls. First Image control display an image in its original size and second
control displays its thumbnail size.
<Window
x:Class="ThumbnailSample.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow"
Height="350"
Width="625">
<Grid
Margin="10,10,10,10"
Name="LayoutRoot">
<Image
Source="Garden.jpg"
HorizontalAlignment="Left"
/>
<Border
BorderBrush="Gray"
BorderThickness="2"
HorizontalAlignment="Right"
Width="130"
Height="130">
<Image
Width="120"
Height="120"
HorizontalAlignment="Center">
<Image.Source>
<BitmapImage
DecodePixelWidth="100"
DecodePixelHeight="100"
UriSource="Garden.jpg" />
</Image.Source>
</Image>
</Border>
</Grid>
</Window>
Listing 40
The output of Listing 40 generates Figure 44
where the left side image is the original image and right side image is the
thumbnail preview of the image.
Figure 44
The code listed in Listing 41 creates a
thumbnail at run-time by creating a BitmapImage object and setting its
DecodePixelWidth and DecodePixelHeight properties.
private
void CreateATyhumbnail()
{
// Create an Image control
Image
thumbnailImage = new
Image();
thumbnailImage.Width = 130;
// Create a BitmapImage and sets its
DecodePixelWidth and DecodePixelHeight
BitmapImage bmpImage = new
BitmapImage();
bmpImage.BeginInit();
bmpImage.UriSource = new
Uri(@"Garden.jpg",
UriKind.RelativeOrAbsolute);
bmpImage.DecodePixelWidth =
120;
bmpImage.DecodePixelHeight =
120;
bmpImage.EndInit();
// Set Source property of
Image
thumbnailImage.Source = bmpImage;
LayoutRoot.Children.Add(thumbnailImage);
}
Listing 41