How Do I Capture Image From WPF Image Control?

One approach could be to create a RenderBitmapTarget and draw the source image onto that. And then use that as the source of another Image.

Consider this example;

<window x:class="WpfApplication9.MainWindow" xmlns:x="#unknown">
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MyAwesomeWindow" Height="350" Width="525">
    <grid>
        <grid.rowdefinitions>
            <rowdefinition height="*" />
            <rowdefinition height="*" />
            <rowdefinition height="Auto" />
        </grid.rowdefinitions>       
        <image x:name="Src" grid.row="0" source="C:\Temp\someimage.png" />
        <image x:name="Dst" grid.row="1" />
        <button grid.row="2" content="Do it!" click="ButtonBase_OnClick" />
    </grid>
</window>

With the backing code of;

using System.Windows;
using System.Windows.Media.Imaging;
using System.Windows.Media;

namespace WpfApplication9 {
    public partial class MainWindow : Window {
        public MainWindow() {
            InitializeComponent();
        }

        private void ButtonBase_OnClick(object sender, RoutedEventArgs e) {
            var visual = new DrawingVisual();
            var context = visual.RenderOpen();

            // Copy source image over
            context.DrawImage(Src.Source, new Rect(0, 0, Src.Source.Width, Src.Source.Height));
            // You can also draw whatever you like on this!
            context.DrawLine(new Pen(Brushes.PeachPuff, 4.0), new Point(0, 0), new Point(100, 100));
            context.Close();

            var renderTarget = new RenderTargetBitmap((int)Src.Source.Width, (int)Src.Source.Height, 96, 96, PixelFormats.Pbgra32);
            renderTarget.Render(visual);

            Dst.Source = renderTarget;
        }
    }
}

In the above example the image, as rendered onto the top image, Src, is draw onto the Dst image when the button is clicked. As the RenderContext is available you can manipulate the image any which way you like.

Hope this helps,
Fredrik