GrabSprite makes black transparent

[coco2]

Possible bug?

Code: Select all

OpenWindow(0, 100, 100, 500, 500, "Test GrabSprite", #PB_Window_SystemMenu | #PB_Window_ScreenCentered)
InitSprite()
OpenWindowedScreen(WindowID(0), 0, 0, 500*DesktopResolutionX(), 500*DesktopResolutionY())
CreateSprite(0, 20, 20, #PB_Sprite_AlphaBlending)
ClearScreen(#Blue)
StartDrawing(ScreenOutput())
Box(240*DesktopResolutionX(), 240*DesktopResolutionY(), 10*DesktopResolutionX(), 10*DesktopResolutionY(), RGBA(0, 0, 0, 255))
Box(250*DesktopResolutionX(), 240*DesktopResolutionY(), 10*DesktopResolutionX(), 10*DesktopResolutionY(), RGBA(255, 255, 255, 255))
Box(240*DesktopResolutionX(), 250*DesktopResolutionY(), 10*DesktopResolutionX(), 10*DesktopResolutionY(), RGBA(255, 255, 255, 255))
Box(250*DesktopResolutionX(), 250*DesktopResolutionY(), 10*DesktopResolutionX(), 10*DesktopResolutionY(), RGBA(0, 0, 0, 255))
StopDrawing()
GrabSprite(0, 240*DesktopResolutionX(), 240*DesktopResolutionY(), 20*DesktopResolutionX(), 20*DesktopResolutionY(), #PB_Sprite_AlphaBlending)
DisplayTransparentSprite(0, 150*DesktopResolutionX(), 150*DesktopResolutionY())
Repeat
Until WaitWindowEvent() = #PB_Event_CloseWindow

[infratec]

Hm ...

black is a special colour.
If you use CreateSprite() the default color is black. And black is used as transparent color.
(You can comment out your blck boxes to see that)

If you use 1, 1, 1, 255 as color, it works as expected,

https://www.purebasic.com/documentation ... prite.html

[coco2]

Black doesn't need to be a special colour does it? Perhaps this is some legacy code going back to the early days?

[infratec]

https://www.purebasic.com/documentation ... prite.html

[coco2]

Isn't it unnecessary to have a certain colour as transparent on 32 bit graphics with an alpha channel?

[DarkDragon]

Isn't it unnecessary to have a certain colour as transparent on 32 bit graphics with an alpha channel?

Nowadays, yes. IIRC this command is from DX7 times where blitting was still used.

[coco2]

I will set all my sprites to #Magenta and try to remember it.

[DarkDragon]

I will set all my sprites to #Magenta and try to remember it.

You can also use DisplaySprite instead if you don't want transparency.

[coco2]

You can also use DisplaySprite instead if you don't want transparency.

Thanks for letting me know. It could be used for background sprites etc.

[Olli]

Code: Select all

OpenWindow(0, 100, 100, 500, 500, "Test GrabSprite", #PB_Window_SystemMenu | #PB_Window_ScreenCentered)
InitSprite()
OpenWindowedScreen(WindowID(0), 0, 0, 500*DesktopResolutionX(), 500*DesktopResolutionY())
ClearScreen(#Blue)
StartDrawing(ScreenOutput())
Box(240*DesktopResolutionX(), 240*DesktopResolutionY(), 10*DesktopResolutionX(), 10*DesktopResolutionY(), RGBA(0, 0, 0, 255))
Box(250*DesktopResolutionX(), 240*DesktopResolutionY(), 10*DesktopResolutionX(), 10*DesktopResolutionY(), RGBA(255, 255, 255, 255))
Box(240*DesktopResolutionX(), 250*DesktopResolutionY(), 10*DesktopResolutionX(), 10*DesktopResolutionY(), RGBA(255, 255, 255, 255))
Box(250*DesktopResolutionX(), 250*DesktopResolutionY(), 10*DesktopResolutionX(), 10*DesktopResolutionY(), RGBA(0, 0, 0, 255))
StopDrawing()
GrabSprite(0, 240*DesktopResolutionX(), 240*DesktopResolutionY(), 20*DesktopResolutionX(), 20*DesktopResolutionY(), #PB_Sprite_AlphaBlending)
DisplayTransparentSprite(0, 150*DesktopResolutionX(), 150*DesktopResolutionY())
FlipBuffers()
Repeat
Until WaitWindowEvent() = #PB_Event_CloseWindow

; HomeBoard indexAll times are UTC+01:00

[SPH]

@Olli :

Completely black in your code !

[Olli]

@sph

We have a real black. As you can see, and conforming to the title description, the problem is solved also !!

Also, in 2010, G-ROM told the order of 'clearScreen', 'examineKeyboard' and 'examineMouse' might be kept on Linux.

[Olli]

I am writing a full screen small example.
Since then 4.40, I think, we can open and close, a full screen and a windowed screen on the fly.

[Olli]

You set the alpha after having grabed.

Code: Select all

StartDrawing(SpriteOutput(0) )
 DrawingMode(#PB_2DDrawing_AlphaChannel)
 Box(0, 0, OutputWidth(), OutputHeight(), RGBA(0,0,0,255) )
StopDrawing()