Cannot convert type 'System.Windows.Media.DrawingImage' to 'System.Windows.Media.Imaging.BitmapSource'

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Hi,

I am trying to create a bitmap source from a System.Windows.Media.Drawing image. Can someone help, not sure how to convert. Here's my code:

C#

var encoder = new PngBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create((BitmapSource)imgsrc.Source));
using (FileStream stream = new FileStream(saveFileDialog.FileName, FileMode.Create))
                    encoder.Save(stream);

When my imgsrc is one that has been created using a bitmap source, the code above works fine. BUT when my imgsrc object was created using a DrawingImage object, an exception is thrown saying:

Unable to cast object of type 'System.Windows.Media.DrawingImage' to type 'System.Windows.Media.Imaging.BitmapSource'.

Thanks in advance!

Posted 21-Sep-13 11:34am

mccaber82

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Richard MacCutchan 22-Sep-13 3:23am

The error is quite clear, a DrawingImage is not related to a BitmapSource, so you cannot cast it. You need to find a method that will convert it.

Richard MacCutchan 22-Sep-13 7:17am

Try a Google search and see what hits you get.

Richard MacCutchan 22-Sep-13 7:44am

And being too lazy to do your own research is not very constructive either.

Richard MacCutchan 22-Sep-13 8:47am

It certaibnly wasn't obvious from your question which implies that you do not understand the difference between casting and converting. As to the actual Google search, how is it that you did not find any of these links, which suggest more than one way to do it?

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mccaber82 · Answer 1 · 2013-09-24T23:07:00

For anyone else that needs a hand working this out, I created two extension methods to convert back and forward between DrawingImage and BitmapSource:

To BitmapSource:

C#

public static BitmapSource ToBitmapSource(this DrawingImage source)
{
     DrawingVisual drawingVisual = new DrawingVisual();
     DrawingContext drawingContext = drawingVisual.RenderOpen();
     drawingContext.DrawImage(source, new Rect(new Point(0, 0), new Size(source.Width, source.Height)));
     drawingContext.Close();

     RenderTargetBitmap bmp = new RenderTargetBitmap((int)source.Width, (int)source.Height, 96, 96, PixelFormats.Pbgra32);
     bmp.Render(drawingVisual);
     return bmp;
}

To DrawingImage:

C#

public static DrawingImage ToDrawingImage(this BitmapSource source)
{
     Rect imageRect = new Rect(0, 0, source.PixelWidth, source.PixelHeight);
     ImageDrawing drawing = new ImageDrawing(source, imageRect);
     return new DrawingImage(drawing);
}