Is there an iphone app that will adjust the size of images to fit instagram?

I've never really cared before… But I've been trying to upload holiday pictures (family, tree, etc) and it got me thinking about it. I have the app squareready, but it just expands the picture and leaves white sides. I prefer for the image to fit the actual square of instagram. Is there an app that will do that? It will reduce the images size to fit the dimensions of instagram? I'm just curious. It would make uploading and taking decent pictures a lot easier.

The iPhone camera app has the option to take square pictures from it now. Slide across & you should come across it. Try that.