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OpenGL - Problem with texture color not correct
Quite a regular
Quite a regular


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Hi All,
I don't think my problem is the "green texture" bug ...
When I create a texture color are messed.

Red -> Red
Green -> Pink
Blue -> Yellow
Red + Green -> Pink
Red + Blue -> Red
Green + Blue -> White
Red + Green + Blue -> White

Does someone know from where it can came ?

I use a RGBA raw file format ( 8 bytes for each component ). I create texture in GL_RGBA internally and use data format GL_RGBA with GL_UNSIGNED_BYTE ...

All we have to decide is what to do with the time that is given to us.
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Re: OpenGL - Problem with texture color not correct
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@freddix

The colour channels of the source image are probably different from what OpenGL expects.

Hans

http://hdrlab.org.nz/ - Amiga OS 4 projects, programming articles and more.
https://keasigmadelta.com/ - more of my work
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Re: OpenGL - Problem with texture color not correct
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@Hans
Theorically not because I've made on my PC a program that write byte per byte the pixels and it stores them in that order : RED, GREEN, BLUE, ALPHA...

And I've found the problem... I use RGBA on my Amiga but I must store image pixels in that order : ALPHA, BLUE, GREEN, RED ...

Is this normal ?

All we have to decide is what to do with the time that is given to us.
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Re: OpenGL - Problem with texture color not correct
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@freddix

I'm not an expert but has something to do with little-endian / big-endian stuff?

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Re: OpenGL - Problem with texture color not correct
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@freddix

Yes this is normal, PC graphic card was designed for PC (x86), not for PowerPC.

You will find the same problem on the screens bitmap, her it was GBAR in 32bit.

Anyway 16bit graphics is horrible, now when I do graphic routines, I operate whit two color formats native and ARGB, normally on load time I convert all my images to native color format in the right pixel depth, this so I do simple copy pixel for pixel every thing.


Edited by LiveForIt on 2009/4/7 2:38:15
(NutsAboutAmiga)

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Re: OpenGL - Problem with texture color not correct
Quite a regular
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@LiveForIt
Ok, so even if OpenGL said RGBA, it's in fact ABGR ... Right ?

All we have to decide is what to do with the time that is given to us.
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Re: OpenGL - Problem with texture color not correct
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@freddix

Quote:

freddix wrote:
@Hans
Theorically not because I've made on my PC a program that write byte per byte the pixels and it stores them in that order : RED, GREEN, BLUE, ALPHA...

And I've found the problem... I use RGBA on my Amiga but I must store image pixels in that order : ALPHA, BLUE, GREEN, RED ...

Is this normal ?


If you're writing the elements byte by byte (i.e., into a uint8*/unsigned char* buffer) then it should work the same way if the OpenGL program is run on a PC or the Amiga. IIRC, I had to perform byte-swapping when using OpenGL under windows too, but I can't remember what the source format was.

Hans

http://hdrlab.org.nz/ - Amiga OS 4 projects, programming articles and more.
https://keasigmadelta.com/ - more of my work
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