TGA transparent texture

Finally, I know what the gl_modulate of the texture is.

For a transparent channel image, you must set gl_texture_env_mode to gl_modulate in addition to saving the internal data for rgba during texture textures.

Glteximage2d (gl_texture_2d, 0, 4, size, size, 0/* no border */, gl_rgba, gl_unsigned_byte, Buf );
Gltexenvf (gl_texture_env, gl_texture_env_mode, gl_modulate );

In this case, the transparent channel instead of the glcolor Alpha value is used in the blend operation. Texture:

Glblendfunc (gl_src_alpha, gl_one_minus_src_alpha); // The src_alpha here is the data of the alpha channel of the texture.