OSD: No no alpha transparency when working in buffer?

[Erstam]

I'm currently testing the OSD. Drawing text to screen with transparent background works fine. But when I work on the buffer the transparency is lost.

Here is the code:



1 function OnPaint()
2 print('Paint')
3 myosd:CopyBufferToScreen()
4 end
5
6 if ( myosd ~= nil ) then
7 myosd:Destroy()
8 myosd=nil;
9 end
10
11 if ( myosd == nil ) then
12 myosd = osd.CreateOSD(0)
13 myosd:Topmost(true)
14 end
15
16 myosd:OnEvent(osd.OnPaint,OnPaint);
17
18 green = osd.MakeARGB(255,0,255,0)
19 trans = osd.MakeARGB(0,0,0,0)
20 greenbrush = osd.CreateSolidBrush(green)
21 transbrush = osd.CreateSolidBrush(trans)
22
23 OSDtext = "Zoom Player"
24
25 w,h=myosd:MeasureString(OSDtext,"Arial",36)
26 myosd:Size(w+10,h+10)
27 myosd:Position(100,100)
28
29 myosd:WorkOnBuffer(true)
30 myosd:FillRectangle(0,0, w+10,h+10, transbrush);
31 myosd:DrawString(OSDtext,"Arial", 36,5,5, greenbrush)
32 myosd:WorkOnBuffer(false)
33 myosd:Show()

When I remove lines 16, 29 and 33 and put line 32 to line 28 then the transparency works.

Is the buffer not capable of alpha transparency?

Erstam

[Erstam]

I have to correct myself: Drawing text to screen with transparent (alpha transparent) background works, but the transparent background of the OSD does not update. If I move a window below the OSD, it does not shine through.

If I use the "SetTransparancy" method, updating works (in both buffered and unbuffered mode), but that is just a workaround, since it defines a whole color (a RGB value, not an ARGB value) as having a certain transparency.

BTW: The method "SetTransparancy" is misspelled. Shouldn' it be "SetTransparency"?

Erstam

[birty]

Transparancy is probably just the american spelling, the english spelling is indeed Transparency

[Mark F]

Nope. We don't spell anything having to do with see-through-colour as "Transparancy". :D

[Ron]

hmm, so what IS the proper US spelling?

[Mark F]

As Birty said: transparency

[Ron]

Thanks!

[Erstam]

Ok, the spelling issue is resolved now, but the original problem still is present.

There seems to be something wrong with alpha transparency or I'm to dumb to understand this thing correctly. Here is what I think: With osd.MakeARGB(a,r,g,b) I can select an RGB value and an alpha transparency that controls the opacity of the color (from 0 = completely transparent to 255 = solid color).

However the attached script does not produce a semi-transparent red background, instead it is solid.

If I specify the semi-transparent red color with the SetTransparency function, not only this color, but every other is semi-transparent as well.

Could you have a look into this issue?

Erstam

[Promixis]

Have you looked at the osd.lua file? The code there will help. I use OSD:Clear (transparentcolor) which seems to work. See line 797 of the Text class and also look at the base class.

[Erstam]

Maybe I'm to dumb. I followed you advice with OSD:clear. The following snippet should create an OSD with a semi-transparent red background. "red50brush" is a brush with the ARGB value (128,255,0,0).



movieosd:WorkOnBuffer(true)
movieosd:Clear (osd.Colors.Black) -- required for alpha/transparents osds
movieosd:FillRectangle (0,0,200,150,red50brush)
movieosd:DrawRectangle (0,0,200,150,whitepen)
movieosd:DrawStringFull("Test for alpha transparency","Arial Black",16,10,10,180,130,1,0,whitebrush)
movieosd:Line(10,80,100,130, blackpen)
movieosd:ScaleDrawImage(image, 110,80,80,60)
movieosd:WorkOnBuffer(false)
movieosd:CopyBufferToScreen()
movieosd:Show()


But unfortunately the background is not transparent (as the attached image shows).

Can you give me a hint to what I did wrong?

Erstam

[Promixis]

Hi,

can you post the entire lua snippet. I don't see anything obvious...

[Erstam]

Here you are!

[Promixis]

you had

movieosd:SetTransparency(red50,128)


commented out. it works here ;)

[Erstam]

When I use SetTransparency not only the color I specify is transparent but also everything else (as the attached picture shows). How can I just set the background to semi-transparent?

And if I need SetTransparency, what does that alpha value in MakeARGB do?

Erstam

[birty]

i think the alpha value is mainly for drawing one osd item on top of another, for example you could draw a box and have the background colour of the osd come through

[Ron]

Correct the alpha value is just for drawing osd items over eachother. If you want a transparant window you'll use SetTrancparancy. This one can do 2 things. either make the whole window transpararent as per your screenshot or just key out 1 color.

[Erstam]

Ok, that clears things up.

But how do I key out just one color? In my screenshot I used movieosd:SetTransparency(red50,128), so I expected it to just key out the red50 with 50% transparency. But instead the whole osd became semi-transparent.

Erstam