The plugin Curves 2, allows to apply a curve with easily controllable shape characteristics. With only three parameters (contrast, brightness, bias) , you can retouch pictures in a breeze. Additionally eight thumbnails allows an intuitive access to eight interesting presets.
New in version 2: Three parameters to control the curve. Invert button and preserve hue option.
Example 1: If you apply a curve with extreme settings ( here : contrast=60, brightness=-30, bias=35) , some hue shifts can appear. On the right pic below, the orange turns to red. You can prevent this by checking the option "Preserve Hue" (center pic below) .
Curve + PH
Example 2: The css button below was obtained by using a texture of "mortar". We were able to obtain two variations of this texture by using curves. Put the cursor over the button to test it.