In WPF 4.0: How to render to a (PNG) bitmap as good as to the window?

Question

I'm exporting my WPF (4.0) visuals (vector diagrams) to some image formats in the next way...

    public void ExportImageTo(BitmapEncoder Encoder, Stream ExportStream, Visual SourceVisual, int Width, int Height)
    {
        var Result = new RenderTargetBitmap(Width, Height, WPF_DPI, WPF_DPI, PixelFormats.Default);
        Result.Render(Source);

        Encoder.Frames.Add(BitmapFrame.Create(Result));
        Encoder.Save(ExportStream);

        ExportStream.Flush();
        ExportStream.Close();
    }

The problem is that even using a PngBitmapEncoder (loseless algorithm) it still generates some little pixels that differs from those in the screen.

I think it is related with the way WPF renders text or deals with anti-aliasing and for which exists properties like UseLayoutRounding, SnapsToDevicePixels and BitmapScalingMode (note: I'm not using those properties on my code).

So, what can I do to make my exported visuals look like those rendered on screen? Thanks!

score 1 · Answer 1 · answered Aug 04 '12 at 05:47

Apparently WPF doesn't render ClearType text if it's targeting a transparent background (google this: RenderOptions.ClearTypeHint). I wonder if you would have better success with a 24bit image format (no alpha channel). Also, Width/Height are not the same as ActualWidth/ActualHeight.

In WPF 4.0: How to render to a (PNG) bitmap as good as to the window?

1 Answers1