How to CROPPING image with C# in WP7

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C#

image

image-processing

I Have hard problem i can't fix it my self.
I want to cropping image1 and after get picture from camera task.

private void button1_Click(object sender, RoutedEventArgs e)
{
    CameraCaptureTask task = new CameraCaptureTask();
    task.Completed += (s, evt) =>
    {
        if (evt.Error == null && evt.TaskResult == TaskResult.OK)
        {
            bmpImage.SetSource(evt.ChosenPhoto);
            image1.Source = bmpImage;
        }
    };
    task.Show();
}

exp: image1 have resolution 1000px * 1000px

now I want add button2 to crop image in image1:
from x=100 to x=800
from y=200 to y=700
so I have new imgae1 resolution 700*500.
I Found Solution for this in http://msdn.microsoft.com/en-us/library/ms752345.aspx[^]
here the code:

// 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.
             
            CroppedBitmapcb = new CroppedBitmap(
               (BitmapSource)this.Resources["masterImage"],
               new Int32Rect(30, 20, 105, 50));       //select region rect
            croppedImage.Source = cb;                 //set image source to cropped

The code above is error the namespace 'CroppedBitmap' not found.
please help my problem