Letter in black?

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Started by yot September 23, 2001 10:34 AM

4 comments, last by yot 22 years, 6 months ago

yot

122

Author

September 23, 2001 10:34 AM

hi, no, I''m NOT going to make a new film called Letter in black

I have prob with fonts. I have a routine that loads a font from a .tga file. Each Letter is within a black box, which means I have a black box on the screen and within the letters. I wanted to know how to remove this black box, so that the letters are drawn without any kind of border. I tried a way with glBlendFunc, but after thinking about it, I saw that this wouldn''t make any sense, because the letters would be also influenced and not only the black shit. Thx for your advise yot

DeschutesCore

122

September 23, 2001 11:24 AM

if you''re using tga files, use the available alpha channels. Both photoshop and Pain Shop Pro support alpha channels. More or less, you need to invert the black portion of the tga image to an alpha layer.

Best of luck,
Jason

yot

122

Author

September 23, 2001 01:10 PM

hi,

thx for advise, I already thought about that, but isn''t there any other way? It must be possible disable one color like in DirectX...

yot

Wavarian

850

September 23, 2001 06:20 PM

I think you should take DeschutesCore''s advice. The only other way is to use depthmasks, which aren''t only twice as annoying but also twice as slow. (since you need to work with two contrasting images of the same letter).

Using the alpha channel in a tga file has got to be one of the easiest ways to accomplish what you''re trying to do in opengl.

brettporter

122

September 24, 2001 06:21 AM

If you don''t want to screw with the TGA in the paint program, screw with it when you load it. It is appalingly easy to do a colour key (the thing in DX which I believe isn''t supported anymore? Maybe just not in DDraw).


for each pixel
  if pixel.r = pixel.g = pixel.b = 0 then
    pixel.alpha = 0.0f
  else
    pixel.alpha = 1.0f

Of course your implementation depends on how you loaded the pixel values etc.

~~~
Cheers!
Brett Porter
PortaLib3D : A portable 3D game/demo libary for OpenGL
Community Service Announcement: Read How to ask questions the smart way before posting!

~~~Cheers!Brett PorterPortaLib3D : A portable 3D game/demo libary for OpenGLCommunity Service Announcement: Read How to ask questions the smart way before posting!