A few days ago I got a help request from a user: "How do you change pixel color during the iteration with ImagickPixelIterator". My initial response was that ImagickPixelIterator is read-only. Well, I have to admit I was wrong. After searching trough ImageMagick docs I stumbled across an example and noticed that PixelIterator (and therefor ImagickPixelIterator) is not read-only after all.

He illustrates with a code example, one showing how to make the object from an image and how to update every second pixel to be black. Source and result images are also included.