Color spaces, gamma and image enhancement

Question

Color space. Well, everybody knows about RGB: three values normalized in the range [0.0,1.0], which have the meaning of the intensity of the color components Red Green

Answer 1

Wait, all this information for what? If I can use sRGB framebuffer and load sRGB textures, process that textures without sRGB conversions... why should I correct gamma?

Generally, you don't. The purpose of the sRGB texturing and framebuffers is so that you don't have to manually do gamma correction. Reads from sRGB textures are converted to a linear colorspace, and writes to sRGB framebuffers take linear RGB values and convert them to sRGB values. This is all automatic, and more to the point free, performance-wise.

The only time you will need to do gamma correction is if the monitor's gamma does not match the sRGB gamma approximation of 2.2 gamma. Rare is the monitor that does this.

Your textures do not have to be in sRGB colorspace. However, most image creation applications will save images in sRGB and works with colors in sRGB, so odds are most of your textures are already in sRGB whether you want them to be or not. The sRGB texture feature simply allows you to actually get the correct color values, rather than the color values you've been getting up until now.

And brightness and contrast: shall they applied before or after gamma correction?

I don't know what you mean by brightness and contrast. That's something that should be set by the monitor, not your application. But virtually all math operations you will want to do on image data should be done in a linear colorspace. Therefore, if you are given an image in the sRGB colorspace, you need to linearize it before you can do any math on it. The sRGB texture feature makes this free, rather than having to do complex shader math.