Canvas to WriteableBitmap

Question

Hello.

I'm imported an images and loaded in a WriteableBitmap.

Then i loaded that image in a Image variable. I need to draw a simple square . For that my next step was to load the Image variable in a canvas. Using a polygon i was able to draw a simple square and show in the app as canvas, but i need save as WriteableBitmap. I tried to use:

RenderTargetBitmap renderBitmap = new RenderTargetBitmap();

          await renderBitmap.RenderAsync(canvas);

But the resutl is 0 bytes in renderBitmap.

Answer 1

Hello,

Welcome to Microsoft Q&A!

I checked your code, I found that you haven't rendered your canvas2 into UI, right?

RenderTargetBitmap could only capture content that in the XAML visual tree. That means that you need to render your Canvas first in your UI. For example, add the canvas2 to your page's root element to make it visible. Then you could add the image and call the RenderAsync method to capture the content.

Thank you.

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Answer 2

Thanks Roy:

Let me check if my understanding is correct:

In the UI I created a Grid <Grid x:Name="RenderedGrid"> inside the Grid I made visible canvas2.

After that I done:

RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();

        await renderTargetBitmap.RenderAsync(RenderedGrid, 1432, 625);

        MyImageout.Source = renderTargetBitmap; //For show  in  <Image x:"MyImageout" >