#701 – Dragging an Image Between WPF Applications

You can use drag and drop functionality in WPF to drag an image from one application to another.

In the drag source, you create a DataObject with a bitmap format.  (Click here for ImageToBitmap source code).

        private void Image_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            Bitmap bitmap = ImageToBitmap(e.Source as System.Windows.Controls.Image);

            DataObject data = new DataObject(DataFormats.Bitmap, bitmap);

            DragDrop.DoDragDrop((DependencyObject)e.Source, data, DragDropEffects.Copy);
        }

In the drop target (the application where you want to drop the image), you just set the Source property of an existing Image control to the data obtained from the GetData method.

<Window x:Class="WpfApplication2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Drop Target" Height="350" Width="325"
        AllowDrop="True" Drop="Window_Drop">
    <Grid>
        <Image Name="imgDropHere"/>
    </Grid>
</Window>
        private void Window_Drop(object sender, DragEventArgs e)
        {
            BitmapSource bmSource = (BitmapSource)e.Data.GetData(DataFormats.Bitmap);
            imgDropHere.Source = bmSource;
        }

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#700 – Dragging an Image to Microsoft Word

You can use the drag and drop functionality in WPF to drag an Image control out of the application.  You can drop this image onto a Word document if you convert the image to an enhanced metafile format.

Here’s the code that initiates the drag operation.

        private void Image_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            Bitmap bitmap = ImageToBitmap(e.Source as System.Windows.Controls.Image);

            DataObject data = new DataObject(DataFormats.EnhancedMetafile, MakeMetafileStream(bitmap));

            DragDrop.DoDragDrop((DependencyObject)e.Source, data, DragDropEffects.Copy);
        }

This makes use of a utility function to convert the Image to a Bitmap:

        private Bitmap ImageToBitmap(System.Windows.Controls.Image image)
        {
            RenderTargetBitmap rtBmp = new RenderTargetBitmap((int)image.ActualWidth, (int)image.ActualHeight,
                96.0, 96.0, PixelFormats.Pbgra32);

            image.Measure(new System.Windows.Size((int)image.ActualWidth, (int)image.ActualHeight));
            image.Arrange(new Rect(new System.Windows.Size((int)image.ActualWidth, (int)image.ActualHeight)));

            rtBmp.Render(image);

            PngBitmapEncoder encoder = new PngBitmapEncoder();
            MemoryStream stream = new MemoryStream();
            encoder.Frames.Add(BitmapFrame.Create(rtBmp));

            // Save to memory stream and create Bitamp from stream
            encoder.Save(stream);

            return new System.Drawing.Bitmap(stream);
        }

This also requires a utility function that converts a Bitmap to a stream containing a Metafile, taken from Stack Overflow.

        // From http://stackoverflow.com/questions/5270763/convert-an-image-into-wmf-with-net
        private MemoryStream MakeMetafileStream(Bitmap image)
        {
            Graphics graphics = null;
            Metafile metafile = null;
            var stream = new MemoryStream();
            try
            {
                using (graphics = Graphics.FromImage(image))
                {
                    var hdc = graphics.GetHdc();
                    metafile = new Metafile(stream, hdc);
                    graphics.ReleaseHdc(hdc);
                }
                using (graphics = Graphics.FromImage(metafile))
                { graphics.DrawImage(image, 0, 0); }
            }
            finally
            {
                if (graphics != null)
                { graphics.Dispose(); }
                if (metafile != null)
                { metafile.Dispose(); }
            }
            return stream;
        }

Here’s the code in action:

#699 – Converting an Image Control to a Bitmap

You may want to work with the image from an Image control as a standard Windows bitmap.  You can convert the System.Windows.Controls.Image to a System.Drawing.Bitmap as follows (imgLife is an Image control):

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            RenderTargetBitmap rtBmp = new RenderTargetBitmap((int)imgLife.ActualWidth, (int)imgLife.ActualHeight,
                96.0, 96.0, PixelFormats.Pbgra32);

            imgLife.Measure(new System.Windows.Size((int)imgLife.ActualWidth, (int)imgLife.ActualHeight));
            imgLife.Arrange(new Rect(new System.Windows.Size((int)imgLife.ActualWidth, (int)imgLife.ActualHeight)));

            rtBmp.Render(imgLife);

            PngBitmapEncoder encoder = new PngBitmapEncoder();
            MemoryStream stream = new MemoryStream();
            encoder.Frames.Add(BitmapFrame.Create(rtBmp));

            // Save to memory stream and create Bitamp from stream
            encoder.Save(stream);
            System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(stream);

            // Demonstrate that we can do something with the Bitmap
            bitmap.Save(@"D:\Temp\Life.png", ImageFormat.Png);

            // Optionally, if we didn't need Bitmap object, but
            // just wanted to render to file, we could:
            //encoder.Save(new FileStream(@"D:\Temp\Life-Other.png", FileMode.Create));
        }