Generate image with javascript

Hello, I'm a complete javascript beginner so sorry if I'm just being stupid :o

I wanted to know if it's possible for me to add a picture (as in a .png file) to a page by clicking on something which would then make an image appear on the screen (which I would then want to be able to drag and move but I made a different thread for that question)

I hope this explanation made sense :o Thank you for your time :)

??? Does the .png file already exist, or do you mean you want JavaScript code to create some sort of semi-random image *as if* a file existed?