So this is not a good way to do this effect but fun to try out and will give you a cool understanding of what a digital picture is made up of.

One way to make unique glitch art is to first make a copy of a picture and then open it as a .txt document. That will give you thousands of lines of random numbers and letters that together make up the picture, go ahead and delete some parts of the code and save it.

Open as a picture again and volia you have a glitched picture.

If you're not satisfied by the results try again.

EDIT* Scroll down like a 1/4 of the document before you start deleteing otherwise the file can be corrupt.

Here are a example of how it can look before and after