iTunes API: get 100x100 px icon of an App
app-store, json
Solution
You can do that like this. Let say this is your link: http://a223.phobos.apple.com/us/r1000/049/Purple/e0/ed/59/mzi.qaoavtgs.png
(from "artworkUrl512").
You just have to add .100x100-75 before .png like this http://a223.phobos.apple.com/us/r1000/049/Purple/e0/ed/59/mzi.qaoavtgs.100x100-75.png
Also ju can adjust icon size you need by adding different values like .150x150-75. Only problem is that this -75 part depends on icon size. it can also be -50 for smaller or -65 for middle size icons. I still did not figure that out.
Hope this helps you.
EDIT: You do not have to worry about .jpg or .jpeg. You can replace all with .png it will work.
Problem
I'm using iTunes API to get some informations about apps in App Store. Reading the documentation I saw that "artworkUrl100" parameter, taken from JSON request, will get me a 100x100 icon of the app. I notice that this not works always, and sometimes it contains the url of a biggest icon. Is there a way to get with certainty this icon (100x100 px)?