This addon also works with 1.6 and 1.7.
There is one small issue - after the thumbs are regenerated, at the top of the addon page, the SELECT statement is being echoed (SELECT image FROM pixelpost_pixelpost WHERE id BETWEEN 2 AND 3).
After looking through the code, I commented out line 63 (echo $query;), reuploaded the file, regenerated a few thumbnails successfully, and the select statement has now disappeared.