Did I find a bug in WriteableBitmap when using string literals
- by liserdarts
For performance reasons I'm converting a large list of images into a single image. This code does exactly what I want.
Private Function FlattenControl(Control As UIElement) As Image
Control.Measure(New Size(1000, 1000))
Control.Arrange(New Rect(0, 0, 1000, 1000))
Dim ImgSource As New Imaging.WriteableBitmap(1000, 1000)
ImgSource.Render(Control, New TranslateTransform)
ImgSource.Invalidate
Dim Img As New Image
Img.Source = ImgSource
Return Img
End Function
I can add all the images into a canvas pass the canvas to this function and I get back one image. My code to load all the images looks like this.
Public Function BuildTextures(Layer As GLEED2D.Layer) As FrameworkElement
Dim Container As New Canvas
For Each Item In Layer.Items
If TypeOf Item Is GLEED2D.TextureItem Then
Dim Texture = CType(Item, GLEED2D.TextureItem)
Dim Url As New Uri(Texture.texture_filename, UriKind.Relative)
Dim Img As New Image
Img.Source = New Imaging.BitmapImage(Url)
Container.Children.Add(Img)
End If
Next
Return FlattenControl(Container)
End Function
The GLEED2D.Layer and GLEED2D.TextureItem classes are from the free level editor GLEED2D (http://www.gleed2d.de/). The texture_filename on every TextureItem is "Images/tree_clipart_pine_tree.png"
This works just fine, but it's just a proof of concept. What I really need to do (among other things) is have the path to the image hard coded. If I replace Texture.texture_filename in the code above with the string literal "Images/tree_clipart_pine_tree.png" the images do not appear in the final merged image. I can add a breakpoint and see that the WriteableBitmap has all of it's pixels as 0 after the call to Invalidate.
I have no idea how this could cause any sort of difference, but it gets stranger. If I remove the call to FlattenControl and just return the Canvas instead, the images are visible. It's only when I use the string literal with the WriableBitmap that the images do not appear.
I promise you that the value in the texture_filename property is exactly "Images/tree_clipart_pine_tree.png". I'm using Silverlight 3 and I've also reproduced this in Silverlight 4.
Any ideas?
