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Rendering RadRichTextPageView to an Image

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Oliver
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Oliver asked on 10 Apr 2011, 02:50 PM
I need to generate a preview thumbnail image of a RadDocument. Unfortunately I cannot get it to work:

DocumentViewManager viewManager = new DocumentViewManager();
XamlFormatProvider xamlProvider = new XamlFormatProvider();
viewManager.Document = xamlProvider.Import(xamlProvider.Export(VM.Document));
viewManager.Document.LayoutMode = DocumentLayoutMode.Paged;
RadRichTextPageView view = new RadRichTextPageView();
view.PageIndex = 0;
ScaleTransform transform = new ScaleTransform();
transform.ScaleX = 0.4;
transform.ScaleY = 0.4;
view.RenderTransform = transform;
view.ViewManager = viewManager;
view.PageIndex = 0;

var writeableBitmap = new WriteableBitmap(200, 200);
view.InvalidateMeasure();
writeableBitmap.Render(Editor, null);
writeableBitmap.Invalidate();

var image = new Image();
image.Width = 200;
image.Height = 200;
image.Source = writeableBitmap;

var wnd = new ChildWindow();
wnd.Content = image;
wnd.Show();

Any suggestions?

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Ivailo Karamanolev
Telerik team
answered on 13 Apr 2011, 11:28 AM
Hello Oliver,

For some reason, when capturing the RadRichTextPageView as a bitmap using WriteableBitmap, Silverlight doesn't render it correctly. We are making an effort to make it work, but we don't currently have a solution to the problem. What we recommend for now is to render the document dynamically using RadRichTextPageView. We are sorry for any inconvenience caused.

Kind regards,
Ivailo
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Oliver
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answered on 13 Apr 2011, 11:59 AM
Ivailo, thanks for the update. What do you mean with "render the document dynamically"?
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Ivailo Karamanolev
Telerik team
answered on 15 Apr 2011, 08:11 AM
Hi Oliver,

I'm sorry I didn't make myself clear. What I meant was, that I recommend you to put a RadRichTextPageView with the document page you want to show (render the document dynamically, instead of statically, e.g. from a pre-rendered bitmap). This will carry a performance penalty, as RadRichTextPageView is much slower than rendering a simple bitmap, but we haven't found a viable solution yet.

All the best,
Ivailo
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Oliver
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answered on 15 Apr 2011, 08:24 AM
I think this is a misunderstanding. My sample code only used the ChildWindow for showcasing the effect. The desired use is to render the thumbnail and store somewhere as JPG.
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Ivailo Karamanolev
Telerik team
answered on 15 Apr 2011, 09:22 AM
Hi Oliver,

Rendering the document on an image using WriteableBitmap produces artifacts. We currently don't know of a way to render the document to an image.

Greetings,
Ivailo
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Oliver
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answered on 15 Apr 2011, 10:18 AM
Yes I've understood that but your last comment sounded a bit like as if you were trying to offer a workaround (which I didn't get by the way :)

One question though, until now I haven't found a single control that refused to render to a WriteableBitmap. How comes the RadRichTextBox is so different?
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Ivailo Karamanolev
Telerik team
answered on 18 Apr 2011, 10:20 AM
Hi Oliver,

Actually, if the RadRichTextPageView is already present in the visual tree and shown on the screen, taking a snapshot of it works correctly. If it is not, however, the text inside it gets overlapped, which is obviously undesired. Unfortunately, adding it to the visual tree on-the-fly doesn't help. We're not sure exactly why Silverlight fails to render it correctly if it hasn't been show previously and thus, we're unable to fix the issue.

Greetings,
Ivailo
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Oliver
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