How to Resolve WriteableBitmap AccessViolationException

Question

I'm currently using the WriteableBitmapEx extension for my writeable Bitmap class. So far everything works now I'm doing this in a WinRT project. I run this code to merge the bitmaps together.

 Windows.Storage.Pickers.FileSavePicker save = new Windows.Storage.Pickers.FileSavePicker();
 save.SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.Desktop;
 save.DefaultFileExtension = ".png";
 save.FileTypeChoices.Add("PNG", new string[] { ".png" });
 StorageFile filesave = await save.PickSaveFileAsync();
 IOutputStream ab = await filesave.OpenAsync(FileAccessMode.ReadWrite);

 if (ab != null)
 {
      //   await _inkManager.SaveAsync(ab);

      var imageUri = new Uri("http://i.imgur.com/rbiLg5Z.gif");
      var fullSizeBitmap = new Windows.UI.Xaml.Media.Imaging.BitmapImage(imageUri);
      // image.Source = fullSizeBitmap;

      var file = await WebFile.SaveAsync(imageUri);
      WriteableBitmap myTempImage = await new WriteableBitmap(1, 1).LoadAsync(file);

      // error!
      myImage.Blit(new Rect(0, 0, 20, 28), myTempImage, new Rect(0, 0, 20, 38));

Now on the line of myImage.Blit I get an unhandled exception for access violation. I really truly don't understand what's going on or what I'm doing wrong. So an help would be appreciated.

Isn't there some code missing above? Add all of it and we might get this sorted :) — Iris Classon

Filip Skakun Filip Skakun · Accepted Answer · 2013-11-21T00:26:41

Most likely either the size of the source or target WriteableBitmap is smaller than the rectangle you pass. Alternatively there might be a bug in one of the methods you are using. Verify the PixelWidth/PixelHeight of the bitmaps you are processing.

How to Resolve WriteableBitmap AccessViolationException

1 Answers