read gray image and color index image.

OpenGL OpenGL: Advanced Coding
1

opengl core profile do not support GL_LUMINANCE and GL_COLOR_INDEX
how can I load texture Minimum Cost(do not convert).
For example, I have a image,8bit gray.Can I no convert to RGB and load to texture?

2

GL_LUMINANCE is replaced by GL_RED.
GL_LUMINANCE8 is replaced by GL_R8.

3

but on opengl 3.3 reference :

GL_RED:Each element is a single red component. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for green and blue, and 1 for alpha.

this mean green and blue is 0,but gray image,green and blue is equal red,isn’t it?

4

In core profile, you will have to do your own fragment program anyway.
So it will end up with something like :

gl_FragColor.rgba = texture2D(texcoord).rrra

5

If you want to play with new functionality (>=GL3.3 or GL2.1 + GL_ARB_texture_swizzle), you can try:


        glTexParameteri(target, GL_TEXTURE_SWIZZLE_G, GL_RED);
        glTexParameteri(target, GL_TEXTURE_SWIZZLE_B, GL_RED);
6

thanks.Now I can handle grey image.

then index image (can get Palette,and data is Palette’s index);
I have to load two texture ,one is index data,Another is Palette data?