"Out of Memory" Errors with GDI+ TextureBrush

The TextureBrush class lets you draw a shape using an image as a texture, giving you some control over the way the texture is tiled.  I encountered a forum post where a user was trying to use TextureBrush to draw sprites to the screen, but he was upset because as he moved the rectangle around it wasn’t moving the texture; the result was similar to having a tiled background covered up and viewed through a small window, then moving the window around.

I looked at the documentation, and saw constructors that let you specify a bounding rectangle.  I misinterpreted what the bounding rectangle did, and thought it specified where the top-left corner of the tiling should start.  The odd thing was introducing this rectangle led to a generic GDI exception with the message "Out of memory."  I found this curious.  At this point I realized that for the problem at hand, there was no reason to use a TextureBrush as opposed to Graphics.DrawImage, so I suggested this course of action.  Of course, I was curious why there was an out of memory exception, so I dug deeper.

Google was no real help; there were basically two forum threads about the problem, and none had a resolution (one suggested a possible accidental recursive paint handler, but that’s ridiculous since the second message wouldn’t be processed until the first completes and it had nothing to do with this case.)  I was about to turn to the MSDN forums when I dug about in the Connect area for any bug reports concerning this.  I found my answer, but it’s somewhat unsatisfactory.

Consider the example image below; it’s a 50×40 image lifted from the VS 2008 image library that represents 2 16×16 images:


We can use a TextureBrush to draw rectangles using this image; by default the result is a silly tiling of back/forward buttons, and if we move the rectangle around it will look as if we’re sliding a window over a fixed pattern, as described above.  If we specify a bounding rectangle, only the part of the image within the bounding rectangle will be used as the tile.  For example, the following paint handler would tile only the left-facing arrow from the above image:

    Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
        Dim g As Graphics = e.Graphics
        Dim boundRect As Rectangle = New Rectangle(7, 12, 15, 15)
        Dim brush As New TextureBrush(drawImage, boundRect)
        g.FillRectangle(brush, Me.ClientRectangle)
    End Sub

If the bounding rectangle that is specified is outside the bounds of the image that is to be tiled, you get the "Out of Memory" exception.  I don’t understand why there’s no error checking done; it would be trivial to check whether dstRect is outside of the bounds of image, but for whatever reason this was left out of the method and instead you get a cryptic error message that doesn’t really tell you what is wrong.

I hope this ends up on Google and anyone who has the problem in the future finds it helpful.

To demonstrate using TextureBrush in the manner the user wanted, the application below animates a left or right arrow back and forth across the form.  I don’t believe this is the best way to do this, and I’m almost certain that one of the Graphics.DrawImage overloads would be more appropriate, but there could be a use for this I have not forseen:

Public Class Form1

    Dim drawImage As Image
    Dim boundRect As Rectangle
    Dim leftPoint As New Point(7, 12)
    Dim rightPoint As New Point(28, 12)
    Dim tileSize As New Size(15, 15)
    Dim viewRect As New Rectangle(New Point(0, 0), tileSize)
    Dim goingLeft As Boolean = False

    Public Sub New()

        ' This call is required by the Windows Form Designer.

        ' Add any initialization after the InitializeComponent() call.

        drawImage = Image.FromFile("Back_Forward.png")

        Dim timer As New Timer()
        timer.Interval = 100
        AddHandler timer.Tick, AddressOf TimerOnTick

        boundRect = New Rectangle(rightPoint, tileSize)
    End Sub

    Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
        Dim g As Graphics = e.Graphics

        Dim brush As New TextureBrush(drawImage, boundRect)
        brush.TranslateTransform(viewRect.X, viewRect.Y)
        g.FillRectangle(brush, viewRect)
    End Sub

    Private Sub TimerOnTick(ByVal sender As Object, ByVal e As EventArgs)
        Dim increment As Integer

        If goingLeft Then
            increment = -10
            increment = 10
        End If

        viewRect.X += increment

        If viewRect.X <= 0 Then
            goingLeft = False
            boundRect = New Rectangle(rightPoint, tileSize)
        ElseIf viewRect.X + viewRect.Width >= Me.ClientRectangle.Width Then
            goingLeft = True
            boundRect = New Rectangle(leftPoint, tileSize)
        End If

    End Sub

End Class

I’m trying Windows Live Writer

From a post on lifehacker I saw that Picasa had labeling/tags (which I didn’t know existed and ended up buying Photoshop Album to make up for).  However, the next post pointed me to Windows Live Photo Gallery, which doesn’t have quite as much polish as Picasa but makes labeling pictures part of the UI instead of a secondary feature.  This Windows Life software is pretty nice, and made this blog post (if nothing goes wrong!).

Now I have to tag all of my pictures again :/

Managed DirectX Documentation is Installed in VS 2005 Help

I’m working on some research that involves managed DirectX, and after I read a few chapters of the book Managed DirectX 9 Graphics and Game Programming (which I really recommend — more later) I wanted to look at the documentation for some of the classes that were discussed to get a more in-depth understanding. Try as I might, I couldn’t find the documentation, so I turned to Google for answers. The only reasonably decent hits I found were forum posts dated in 2005 discussing how it was still beta and there was no documentation. Useless. I had almost completed an email to Tom Miller, the author of the book, when I noticed the sentence, “I have looked in the VS 2008, VS 2005, and Windows SDK help…” was false. I had looked in VS 2008 and Windows SDK, but not VS 2005.

So, I’m continuing my series of posts inspired by things I tried to use Google to find but failed. If you want to know where the Managed DirectX documentation is in the March 2008 DirectX SDK, look in the Visual Studio 2005 help.

It’s possible I overlooked an installer option but I’m too lazy to check again.