I am able to upload one picture but I can't create a photoset with multiple images using API.
Documentation says: Paramater: Array (URL-encoded binary contents)
One or more image files (submit multiple times to create a slide show)
Does anyone know how to do it?
It's kind of a painful process, but I figured it out after studying the python code Tumblr posted. In short, it requires getting the hexadecimal for the photo and then doing some substitutions.
I've created a simple iOS / iPad / iPhone project on GitHub that uploads multiple photos to photosets using the Tumblr API, based heavily on the ASIHTTPRequest+OAuth project. It works so far in my limited testing -- feel free to make use of it and let me know how it goes.