I have used GraphicConverter since its earliest iterations and have always found it simple and reliable, until I thoughtlessly updated from the App Store. (It has gotten slightly more complicated as numerous new features have been added to accommodate new file types and new approaches to graphics, but not difficult to use.) Via the App Store some functions (saving as SVG, for example) are disabled, for reasons beyond my undrstanding — something to do with playing in the OSX sandbox, I am told!
When I brought my problem to Thorsten Lemke’s attention on a Sunday afternoon, California time, he had a reply back to me from Germany before midnight the same day, and had replaced my App-Store App via a direct download link from his site.
Wir danken Dir, Thorsten!