[RESOLVED] Robust response to Out Of Memory Exception

[boops boops]

I've noticed that GDI+ and other graphics can crash when asked to deal with very large images, and the crash doesn't always occur where you'd expect it. I am getting this when testing the slide show program I posted to the code bank yesterday. This is the code concerned:

Private Sub animTimer_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles animTimer.Tick
        If infos.Count = 0 Then Exit Sub
        ticks = (ticks + 1) Mod 200
        Select Case ticks
            Case 0
               'phase 1: Pic2 is shown, Pic1 is hidden. Start loading pic1.
                picIndex = (picIndex + 1) Mod infos.Count
                Pic1.Load(infos(picIndex).FullName)
            Case 50 To 99
                'phase 2: Start fading pic2
                Try
                    PicForm2.Opacity -= 0.02
                Catch Ex As Exception
                    MessageBox.Show(Ex.Message)
                End Try
                If ticks = 65 Then Me.Text = "Easy Slide Show: " & infos(picIndex).Name
            Case 100
                'phase 3: Pic1 is shown. Start loading Pic2
                picIndex = (picIndex + 1) Mod infos.Count
                Pic2.Load(infos(picIndex).FullName)
            Case 150 To 199
                'phase 4: Start Unfading Pic2
                PicForm2.Opacity += 0.02
                If ticks = 165 Then Me.Text = "Easy Slide Show: " & infos(picIndex).Name
        End Select
    End Sub

The crash only occurs when asked to deal with a 48Mpixel (6000 x 8000) image, and then only when running in the debugger. The picture box loads the image successfully and displays it OK. The Out of Memory exception is not thrown until I try to fade the form by changing its opacity (line 12).

Unfortunately Try-Catch doesn't work in this case. If it did I could simply skip the image concerned or maybe show it at a lower resolution. But the OOM error is thrown before the exception is caught. The same applies whether I put Try-Catch just around the offending line as above or round the whole loop.

I realize that a 48 Megapixel image is a lot to ask, certainly in limited memory, and in normal running even that does not fail. But where should I draw the line? Is the only way to set an arbitrary upper size limit to the images to ward off a potential crash? In this application I would prefer just to skip the image if need be. Can someone recommend a robust way to deal with the exception?

BB