GrabImage help

I'm trying to simply draw something on the backbuffer and then copy it to an image but it's not working. It's almost as though GrabImage isn't working as I can confirm the image is being drawn on the back buffer by uncommenting the line near the bottom of the function code.

Strict

Graphics 800, 600, 32

Const TARG_IMAGE_FLAGS:Int = DYNAMICIMAGE | FILTEREDIMAGE | MASKEDIMAGE
Global targ_image:Timage = create_target_image()

While Not KeyHit(KEY_ESCAPE)
	Cls
	DrawImage targ_image, 100, 100
	Flip
Wend

End

Function create_target_image:Timage(size:Int=128)

	Local image:Timage = CreateImage(size, size, 1, TARG_IMAGE_FLAGS)

	SetClsColor 0, 0, 0
	Cls 

	Local rgb:Int = 0
	For Local n:Int = 0 To 19
		SetColor rgb, rgb, rgb
		DrawOval n, n, size-(n*2), size-(n*2)
		rgb :+ 10
	Next

	rgb = rgb - 10
	For Local n:Int = 30 To 49
		SetColor rgb, rgb, rgb
		DrawOval n, n, size-(n*2), size-(n*2)
		rgb :- 10
	Next
	
	'Flip ; WaitKey() 
	
	GrabImage image, 0, 0
	Return image

End Function

Also, any idea why this version crashes, causing me to have to reboot?

Strict

Graphics 800, 600, 32

Const TARG_IMAGE_FLAGS:Int = DYNAMICIMAGE | FILTEREDIMAGE | MASKEDIMAGE
Global targ_image:Timage '= create_target_image()

While Not KeyHit(KEY_ESCAPE)
	Cls
	DrawImage targ_image, 100, 100
	Flip
Wend

End

Function create_target_image(size:Int=128)

	targ_image = CreateImage(size, size, 1, TARG_IMAGE_FLAGS)

	SetClsColor 0, 0, 0
	Cls 

	Local rgb:Int = 0
	For Local n:Int = 0 To 19
		SetColor rgb, rgb, rgb
		DrawOval n, n, size-(n*2), size-(n*2)
		rgb :+ 10
	Next

	rgb = rgb - 10
	For Local n:Int = 30 To 49
		SetColor rgb, rgb, rgb
		DrawOval n, n, size-(n*2), size-(n*2)
		rgb :- 10
	Next
	
	'Flip ; WaitKey() 
	
	GrabImage targ_image, 0, 0
	'Return image

End Function

In the first one, its actually working perfectly except you've got the color set as 0,0,0. Set it back to 255,255,255 after calling create_target_image().

For future reference, SetColor effects the color of everything you draw - images included.

In the second example, you're trying to draw an image that doesn't exist. If you run that in release mode (non-debug) its probably not gonna like it. When I run it with Debug enabled, it tells me that targ_image is a null object (it doesn't exist).

Ah yes, that works, thanks. I did actually read about this but completely forgot about it. :/

Why doesn't the image exist? targ_image is a global so should be assigned the image inside the function, no? Also, I'm using the demo version of bmax which just seems to produce debug builds. I don't get any error message. Strangely though, if I put a DebugStop in the working version, it crashes again and I have to reboot. :/

I also notice that the output window sometimes displays this info at the end. Is this normal? I have no idea what it means.

Well, you've commented out the function call!

Global targ_image:tImage Only says "I want targ_image to be a tImage". Even after you've made the definition, targ_image is still Null - that is, not an object, not zero, but Null. Nothing.

To attach an object, you must use LoadImage, CreateImage, or LoadAnimImage.

Not sure about the other stuff relating to the Blitzmax demo, but rest assured I'm not getting any of that nonsense in Blitzmax 1.30 full version.

lol. I'm a bit rusty at this coding lark but that one's a classic. :p I meant to move the call to a separate line but for some reason I commented it out!

Any idea about the debug strangeness? Like I said, that numpty version didn't throw an error, it just crashed. :/

Nope, no strangeness here. Must be demo-related.

Possibly, or maybe some strangeness related to my PC. I just don't want to buy blitzmax and find the debugger still doesnt work. :S

Thanks for the help.