I would like to be able to implement Bezier-type controls in a Premiere pro CS4 plugin. I saw this kind of control in the "RGB curves" and "luma curve" effects embedded in Premiere, but could not find any info on them in the SDK manual, nor in a general search on the Internet.
These custom controls are implemented using custom ECW UI, using the After Effects API.
You can download the AE SDK here: http://www.adobe.com/devnet/aftereffects.html Check out the Custom ECW UI sample plug-in in that SDK. It has basic compatibility in Premiere Pro.
For questions about the AE SDK, please use the After Effects SDK forum: http://forums.adobe.com/community/aftereffects_general_discussion/aftereffects_sdk