Help with LockedPixels

BlitzPlus Forums/BlitzPlus Beginners Area/Help with LockedPixels

Andres

(Posted 2006) [#1]

can anyone please write me an example or something how to use this command. I tried it but integer returned by the function was always 0 though i locked the buffer?! :S

Matty

(Posted 2006) [#2]

Have a look at this thread, it pretty much shows how to use lockedpixels in a few posts about halfway down:

http://blitzbasic.com/Community/posts.php?topic=27004

It would have been nice to have an example like that in the documentation.

LockBuffer

If LockedFormat(BackBuffer())=4 Then 
;ie 32bit color
LockedBufferBank=LockedPixels(BackBuffer())

pitch=LockedPitch() ;length in bytes of each row of pixels (note it is not necessarily the same length as the buffer width*bitdepth)



;to poke directly to the buffer do this:
;PokeInt lockedbufferbank,4*((ScreenY)*(pitch/4)+ScreenX),RGB

Next



unlockbuffer

Personally I 'love' lockedpixels and blitzplus. I am working on an isometric game that uses a zbuffer and prerendered scenes (also with animated zbuffers/collision maps). All the characters are stored in my own image format - in system memory rather than video memory allowing me to have thousands of frames of animation per character and the ability to still draw hundreds of them at once on screen.

Andres

(Posted 2006) [#3]

LockedPixels isn't faster than WritePixelFast?

Hold down spacebar to use WritePixelFast:

Graphics 320, 240, 32, 1

Global fps#
Global fpstime%

While Not KeyHit(1)
	If Not KeyDown(57) Then
		Draw()
	Else
		Draw2()
	EndIf
	
	CountFPS()
	Color 0, 0, 0
	Rect 10, 10, 100, 20
	Color 200, 200, 200
	Text 10, 10, FPS
	Flip
Wend
End

Function draw()
	LockBuffer
		If LockedFormat() = 4 Then
			LockedBufferBank = LockedPixels()
			pitch = LockedPitch()
			For y = 0 To GraphicsHeight()
				For x = 0 To GraphicsWidth() - 1
					PokeInt lockedbufferbank, 4 * (y * (pitch / 4) + x), (Rand(0, 255) Or (Rand(0, 255) Shl 8) Or (Rand(0, 255) Shl 16) Or ($FF000000))
				Next
			Next
		EndIf
	UnlockBuffer
End Function

Function draw2()
	LockBuffer
	For y = 0 To GraphicsHeight() - 1
		For x = 0 To GraphicsWidth() - 1
			WritePixelFast x, y, (Rand(0, 100) Or (Rand(0, 100) Shl 8) Or (Rand(0, 255) Shl 16) Or ($FF000000))
		Next
	Next
	UnlockBuffer
End Function

Function CountFPS()
	fps = 1000.0 / (MilliSecs() - fpstime)
	fpstime = MilliSecs()
End Function

Matty

(Posted 2006) [#4]

Lockedpixels is not significantly different for altering individual pixels, but for copying entire banks of pixels at once it is very quick using the copybank feature.