Creating a distortion field graphical effects

First, look here: stackoverflow.com/questions/5618962/twirl-and-pinch-effect-to-images-image-distortion-algorithm

See the images of twirl and pinch? If I want to achieve such effect in real time in Construct, how can I do it?

You could use sprite distort maps:

http://dl.dropbox.com/u/5426011/examples12/twist_pinch.cap

Ah, I see. But that's not quite what I have in mind. Is it possible to render the scene into some sort of buffer first, then apply this post-processing step later, then render this buffer on to the layout? Because here, only one Sprite will be affected. What about any Sprite that comes into contact at a particular area will be distorted?

You could use a layer effect, but you'd have to write the shader since one for those effects don't exist AFAIK.

Or you could use a canvas object as it also has distort maps. You could then use paste action to draw the objects into the canvas, or perhaps the grab layout property.

Image manipulator has a few pre-made effects also.