Can you specify tangent slope/strength of control points for Beziers?

OpenGL OpenGL: Advanced Coding
1

Using the standard OpenGL evaluators, can you somehow specify the tangent slope and length (strength) of control points for Bezier curves and surfaces?
Thank you,
Luke

2

If you could, they wouldn’t be Bezier splines anymore. A Bezier spline is defined by 4 positions. Two of them define the end-points of the spline. The other two, one for each point, define the slope of the curve at the anchor points as well as the relative “strength” of the curve.

If you want to define these things more directly, you shouldn’t use Bezier splies.

3

So what is the type of splines used in say Photoshop, where you can adjust the tangent and the strength of ‘influence’ ? I thought those were Beziers, no?
Thanks,
Luke