Brightness & Contrast of Texture


We want to display a gray scale texture. Each pixel=8bits.
We must have a capability to change the contrast and brightness of the texture. The reason for this is that the user has a monitor with no adjustment.
We succeeded doing it with loading a specified color palette and then loading the texture. For this we need the extension: GL_EXT_paletted_texture.
Is there an alternative ?

Zvika Vered