You don't need something as expensive as Photoshop to convert a picture's size and format, programs like ACDSee will let you resize and crop picutures and will load and save in the .png format or you can also change jpegs to .png with it. And the nice thing about ACDSee is it will load up a lot faster and to load an image you just double click on the file in your file folder. I use it all the time to do simple edits such a resizing, cropping, changing hue, brightness, contrast, making thumbnails and converting from one format to another.