TGA vs. BMP

No targa cannot store transparency. However, it uses a different technique called Alpha channels. The level specified in the alpha channel determines whether the colour will be fully transparent or fully opaque or somewhere in between.

Bitmaps are similar, but do not support alpha channels.

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First make it work,
then make it fast.
--Brian Kernighan

"The problems of this world cannot possibly be solved by skeptics or cynics whose horizons are limited by the obvious realities. We need men and women who can dream of things that never were." - John Fitzgerald Kennedy(35th US President)

TGA's can be compressed or uncompressed. BMP only comes uncompressed. BMP is 24 bits (RGB) while TGA can be 24 or 32 bits (RGB or RGBA). TGA's can't store 'regular' transparency as supported by painting programs like PaintShop (that's only for GIFs and the like) but the extra Alpha channel can be used to add transparency in 3D API's like OpenGL and DirectX.

EDIT: Damn.... beaten to it

Sander Maréchal
[Lone Wolves Game Development][RoboBlast][Articles][GD Emporium][Webdesign][E-mail]

[edited by - sander on September 11, 2003 12:54:22 PM]

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Original post by Sander
TGA's can be compressed or uncompressed. BMP only comes uncompressed.

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That is not entirely correct. While most bitmaps you find and indeed most bitmap programs don't use it, the bitmap file format specs do in fact support compression.

quote:

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Original post by Sander
EDIT: Damn.... beaten to it

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By 28 seconds

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First make it work,
then make it fast.
--Brian Kernighan

"The problems of this world cannot possibly be solved by skeptics or cynics whose horizons are limited by the obvious realities. We need men and women who can dream of things that never were." - John Fitzgerald Kennedy(35th US President)

[edited by - CaptainJester on September 11, 2003 1:20:38 PM]

quote:

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Original post by Sander
TGA''s can''t store ''regular'' transparency as supported by painting programs like PaintShop ... but the extra Alpha channel can be used to add transparency in 3D API''s like OpenGL and DirectX.

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What is "regular transparency"? Is that where you specify a color or a palette index as transparent? The alpha channel determines how transparent or opaque each pixel is. How is that different from "regular transparency"?

BTW, TGA''s also support 8-bit, 16-bit, palettized, and greyscale, and more.

quote:

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Original post by JohnBolton
What is "regular transparency"? Is that where you specify a color or a palette index as transparent? The alpha channel determines how transparent or opaque each pixel is. How is that different from "regular transparency"?

BTW, TGA''s also support 8-bit, 16-bit, palettized, and greyscale, and more.

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With regular transparency you choose one colour to be the transparent colour. You therefore cannot use that colour as a displayable colour. And typically regular transparency is only used with an indexed palette. With alpha channels, you can use any colour as the transparent colour, plus you can make some only partially transparent.

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First make it work,
then make it fast.
--Brian Kernighan

"The problems of this world cannot possibly be solved by skeptics or cynics whose horizons are limited by the obvious realities. We need men and women who can dream of things that never were." - John Fitzgerald Kennedy(35th US President)

If you want textures with transparency in opengl, look up libpng.

Hello

I want to use textures with transparency in DirectX? Does anybody know how to do that, or is there any source code out there?

thanks

Again, you can load a png and use that as a texture. ID3DXSprite::LoadTextureFromFile(...) can load a png file, iirc.

In opengl, you will need libpng. It is very easy to use and comes with examples that you can cut and paste into your project.

Its a dandy lib and will sort out all your transparent texture needs. The file sizes are non-lossy compressed, too!

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ID3DXSprite::LoadTextureFromFile(...)

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.lick