Drop a display.newRect() on top of the sprite, make it invisible and .isHitTestable = true. Put them both in a group and always move the group. Put your touch listener on the rectangle.
Generating masks is real easy if you have photoshop. I have a batch script that generates all my 2bit masks from 32bit graphics. The problem with floating a rect over your graphic is you will still get touch events on your transparent areas. Masking is the only way to go (apart from having a polygon that roughly matches your asset which is a major pain!)
I wish Corona supported masks for image sheets - that would be a major bonus.
Drop a display.newRect() on top of the sprite, make it invisible and .isHitTestable = true. Put them both in a group and always move the group. Put your touch listener on the rectangle.
Generating masks is real easy if you have photoshop. I have a batch script that generates all my 2bit masks from 32bit graphics. The problem with floating a rect over your graphic is you will still get touch events on your transparent areas. Masking is the only way to go (apart from having a polygon that roughly matches your asset which is a major pain!)
I wish Corona supported masks for image sheets - that would be a major bonus.