I want to implement Zoom in and Zoom out in my OpenGL application.
Currently I only find from the document that I need to implement call back function for below events:
EVAS_CALLBACK_MULTI_DOWN
EVAS_CALLBACK_MULTI_UP
EVAS_CALLBACK_MULTI_MOVE
But who can help to describe detail how to use these events to realize Zoom in/out like already done in photocam.
How can I recogonize the zoom in/out gesture from multitouch events?