help: Texture from files

hey there!!
i’m new to opengl programming. I’m trying to apply textures from bitmap files to objects. I’m a bit confused by the different formats(BMP, PNG, TGA), and how to read the information from these files. I’m coding in C.
Plz help!

NeHe’s tutorials is what you need.

The quickest hack is to use the TGA file format, and “know” about the image properties beforehand. For instance, if you have a 256x256 RGB (24-bit) image saved as a TGA file, you can load it with the following code (it simply skips the header, which is 18 bytes long):

unsigned char image[ 256*256*3 ];
FILE *f;

f = fopen( "mypic.tga", "rb" );
fseek( f, 18, SEEK_SET );
fread( image, 256*256*3, 1, f );
fclose( f );

Now you can upload it to texture memory with:

glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_BGR, GL_UNSIGNED_BYTE, image );

Note: TGA stores the pixels as BGR, that is why we set format = GL_BGR.

Of course, you will want to add error checking and use memory allocation instead of statically declared variables (remember: you can free the memeory used by a texture once it has been uploaded to the graphics card using glTexImage2D).

To learn more about the contents of the 18-byte TGA file header (or any other file format), go to

[This message has been edited by marcus256 (edited 11-20-2001).]