Is GrabImage safe?

BlitzMax Forums/BlitzMax Programming/Is GrabImage safe?

GfK	(Posted 2011) [#1]

I want to have a pixmap, and draw some text onto it using Ziggy's FontMachine. FontMachine itself does not seem to allow you draw directly onto Pixmaps, though I've asked on the BLIde forum and waiting a reply.

In the meantime, I could achieve the same result by drawing to the backbuffer and using GrabImage but I seem to remember on some PCs, GrabImage, or it might have been GrabPixmap, didn't work for one reason or another.

Anybody shed any light on this? Are either/both these commands to be avoided?

SLotman

(Posted 2011) [#2]

I never encoutered any problem with GrabImage, besides the fact that it is very slow.

And I usually test my games on 13 different computers (from the ones I have, to family and the ones at work) - so you can include nVidia, ATI and Intel chipsets on that test.

Last edited 2011

GfK	(Posted 2011) [#3]

I never encoutered any problem with GrabImage, besides the fact that it is very slow.

I'm not bothered about speed as this is a one-shot thing.

GfK	(Posted 2011) [#4]

Here's some test code. Appreciate it if folks could give this a test - its self explanatory but, draw a load of random circles, grab an image, draw the grabbed image, ESC to exit.

[edit] Updated to include time taken for GrabImage. I get ~360ms which is perfectly acceptable for what I'm using it for.

Strict

Graphics 800,600

For Local n:Int = 1 To 500
	SetColor Rand(0,255),Rand(0,255),Rand(0,255)
	
	DrawOval Rand(0,800),Rand(0,600),Rand(10,50),Rand(10,50)
Next

Local img:TImage = CreateImage(512,512,1)
Local grabtime:Int = MilliSecs()
GrabImage(img,0,0)
DebugLog MilliSecs() - grabtime + "ms taken to grab"
Cls
SetColor 255,255,255

While Not KeyDown(key_Escape)
	Cls
	DrawImage img,MouseX(),MouseY()
	Flip
Wend

Last edited 2011

Jesse

(Posted 2011) [#5]

DebugLog:74ms taken to grab

laptop specs in sig.

I can't remember for sure but I believe DrawPixmap and/or ~~GrabPixmap~~ didn't use to work or doesn't work with DX7 on Vista and windows 7 it might not work with dx9 either on vista and 7.

Last edited 2011

Last edited 2011

ImaginaryHuman

(Posted 2011) [#6]

Never had a problem with grab image or grab pixmap.

col	(Posted 2011) [#7]

Hiya,

Debuglog:300ms taken to grab

on my laptop...
Sony Vaio VGN-FW31M
with Vista SP2 using DX9.

EDIT :- changed the Debuglog to Print and ran in Release mode - got ~240ms.

Last edited 2011

Floyd

(Posted 2011) [#8]

Looks okay here, a bunch of colored ovals.

Times were 150 and 89 for debug and release.

Five year old PC: Win XP with on-board nvidia 6100 ( I think ).

SLotman

(Posted 2011) [#9]

Instead of Debuglog, use print, so you can test it without debug mode, which is much faster.

DX7: 32ms on 'release mode' and 81ms on 'debug mode'.
DX9: 47ms on 'release' and 172ms on 'debug'
OGL: 46ms on 'release' and 84ms on 'debug'

(Laptop, ATI X1300, 1Gb RAM, WinXP)

Last edited 2011

GfK	(Posted 2011) [#10]

Well, as said I'm not overly bothered about how long it takes (unless it takes, like, 5 seconds or something). That's the only reason I put the time check in there.

The only thing I'm really interested in, is whether or not it works. :)

SLotman

(Posted 2011) [#11]

If you need more speed, drawing from pixmap to pixmap with pixmap.paste() is much, much faster.

I was doing a grabimage to generate a 'level preview' in my game... switched to pixmap.paste() and the time went from 150ms to 1ms!
Too bad - afaik - pixmap.paste() doesn't take the alpha channel into account, otherwise it would be pretty handy!

Kryzon

(Posted 2011) [#12]

API calls for OpenGL's GrabImage:

glReadPixels()

API calls for D3D9's GrabImage:

GetRenderTarget()
CreateOffscreenPlainSurface()
GetDC()
BitBlt()
LockRect()

Check the compatibility for these API calls. The rest of code in these functions is plain BMax.

GfK	(Posted 2011) [#13]

Started a new thread here with an EXE to test for those who dont have blitzmax or can't be bothered copying/pasting.

Can a mod lock this please?