Graphics libraries OpenGL, DirectX and game engines such as Ogre3D may be too low level for tasks like drawing shapes and gradients.
Maybe you should take a look at Cairo as mentioned above (http://cairographics.org/), or simply at Qt which has a pretty complete and efficient drawing module (http://qt.nokia.com/doc/4.5/examples.html#graphics-view) and allows high level (GraphicsScene & GraphicsView) and low level (OpenGL) drawing.
