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POWPF resize anti-aliasing artifacts on Windows Server 2003
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  1. POWPF resize anti-aliasing artifacts on Windows Server 2003
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    copied!<p>I am resizing PNG’s in a console app using the following WPF code in .NET 4:</p> <pre><code>const int width = 250; const int height = 179; DrawingGroup group = new DrawingGroup(); RenderOptions.SetBitmapScalingMode(group, BitmapScalingMode.Fant); group.Children.Add(new ImageDrawing(source, new Rect(0, 0, width, height))); DrawingVisual targetVisual = new DrawingVisual(); using (DrawingContext targetContext = targetVisual.RenderOpen()) { targetContext.DrawDrawing(group); targetContext.Close(); RenderTargetBitmap target = new RenderTargetBitmap(width, height, 96, 96, PixelFormats.Default); target.Render(targetVisual); BitmapSource resized = BitmapFrame.Create(target); } </code></pre> <p>When running on Windows 7 this works exactly as expected, but when running on Windows Server 2003 I get what I think are anti-aliasing artefacts.</p> <p><a href="http://i.stack.imgur.com/wQfUp.jpg" rel="nofollow">This Image</a> shows how, when displayed on a web page with a white background, the Server 2003 image has extra horizontal and vertical grey lines in the white area that should not be there.</p> <p>Zooming in on one small section to try and work out what is happening <a href="http://i.stack.imgur.com/r7ljo.jpg" rel="nofollow">this image</a> shows how the original PNG has a 1 pixel semi-transparent line between the transparent section (shown as chequered grey and white) and the white area. Both resized images have the same semi-transparent line but the one under Server 2003 has some weird variations in the level of transparency.</p> <p>There is a good MSDN document on the effects of anti-aliasing when resizing images in WPF (http://msdn.microsoft.com/en-us/library/aa970908.aspx) that would seem to match the symptoms I am seeing here but why would this work differently between Windows 7 and Server 2003??</p> <p>I have tried to find ways to switch of anti-aliasing to test this theory using the following code but it didn’t make any difference:</p> <pre><code>RenderOptions.SetEdgeMode(group, EdgeMode.Aliased); </code></pre>
 

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