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POCopy image with alpha channel to clipboard with custom background color?
 

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    <p><strong>Code :</strong></p> <pre><code>private void Foo(Canvas canvas) { // The content is a bit larger... Size size = new Size(canvas.ActualWidth * 1.1, canvas.ActualHeight * 1.2); // Create a render bitmap and push the surface to it RenderTargetBitmap renderBitmap = new RenderTargetBitmap( (int)size.Width, (int)size.Height, 96d, 96d, PixelFormats.Pbgra32 ); renderBitmap.Render(canvas); // Then copy to clipboard Clipboard.SetImage(renderBitmap); } </code></pre> <p><strong>What I need :</strong></p> <p>Render a canvas with transparent background to image, then copy it to clipboard (Quit simple? Not really)</p> <p><strong>Problem :</strong></p> <p>When paste, I get a ugly image with black background</p> <p><strong>Solution 1 :</strong></p> <pre><code>canvas.Background = new SolidColorBrush(Colors.White); </code></pre> <p>No. This thick do not work, the background of <code>canvas</code> will not change in the next <code>renderBitmap.Render(canvas);</code></p> <p>Instead, I have to use a timer, give WPF some time to change the background, then render it in the tick event of that timer. It works, but unfortunately, the content of <code>canvas</code> is larger than it's size...so the white background can only cover part of it, still ugly result. (BTW anyone know why it takes sometime to change the background? I thought it should be changed instantly)</p> <p>Did I do something wrong? How can I get a white background ex-transparent image in clipboard?</p> <p>What's more, I've noticed that the background of some PNG images remain white if you paste it into mspaint.exe which do not support alpha channel, but some others become black.</p> <p>Is there something like, say, <code>alternative color</code>, which is used as background if the place where you paste your image do not support alpha channel? Can we custom it?</p> <p>Now I rendered another <code>BitmapSource</code> with white content, if there is a way to combine it with the <em>renderBitmap</em> as background, the problem solved, but I don't know how...</p> <pre><code>int dWidth = (int)size.Width; int dHeight = (int)size.Height; int dStride = dWidth * 4; byte[] pixels = new byte[dHeight * dStride]; for (int i = 0; i &lt; pixels.Length; i++) { pixels[i] = 0xFF; } BitmapSource bg = BitmapSource.Create( dWidth, dHeight, 96, 96, PixelFormats.Pbgra32, null, pixels, dStride ); // Combine bg with renderBitmap </code></pre>
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      1. USJesse Seger
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    1. COIt appears to save the bitmap after removing the alpha channel instead of all channels. Is the image on the clipboard an MS BMP?
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      1. USCole Johnson
    2. CO@ColeJohnson I don't know. As the results I've searched, seems MS clipboard image do not support transparent channel. I'm trying to find a way add a white background for this image before set it to clipboard
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      1. USByzod
    3. COyou can always base64 encode it and base64 decode it on the other end. But that might break compatibility. For apps with images, I don't know how they do it `:(`
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      1. USCole Johnson
 

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