I want to make a stretch effect? I'm trying to make an effect using the Blender Compositor, but I didn't know how to do it, and please I want the solution using the compositor not by adding more objects (Lens).

Here is a picture to explain what I want to do :
Final result:



Composition nodes:



Overview:

I don't know your scene setup but mine is just plane with procedural stripes.

After render you just need to connect couple of sets - Lens Distortion + Scale nodes and adjust values as you like. X value will stretch pattern, Y is for straightening up after Lens Distortion.

Blend file: