Using Corona SDK, I want to be able to determine if a sprite frame is blank and if so disregard it.
In my workflow, I'm using a perl script to automatically create a bunch of equally-sized, square, image/sprite sheets from multiple individual images (using the 'montage' command-line tool from ImageMagick).
Obviously, depending on the original image dimensions, the final few frames of the final image sheet may be blank/transparent (in other words if I generate a bunch of image sheets each with 4 x 5 frames and I originally have 57 images, I will have 2 image sheets of 20 frames each and my final image sheet will have 17 frames with 3 blank frames in its final row).
I don't want the code in my Corona app to be dependent on the number of images/frames, etc. so I want my code to treat each of my image sheets the same (I'm creating an animation that spans multiple image/sprite sheets). Obviously I don't want to display a couple of blank frames in my animation, so my question is can I process each frame in real time to determine its transparency, or otherwise do some sort of pixel analysis to see if I need to disregard the frame?
Maybe I made this sound more complicated than it actually is...
Ok, simpler question: is it possible to access the pixel data of an image in Corona to get the alpha values?
Corona SDK does not give you access to pixel level data, so the answer to both questions is No, you cannot. This is a very frequently asked for feature, but the way Corona SDK uses the OpenGL layer, it makes getting this information very difficult.