For each image uploaded to your WordPress.com blog’s Media Library, you have some basic editing options (crop, rotate, flip, and resize) available.

You can rotate (clockwise or counter-clockwise) any image in your media library using the appropriate icons above the image in its editing screen.

You can flip (vertically or horizontally) any image in your media library using the appropriate icons above the image in its editing screen.

You can proportionally scale any original image in your Media Library. For best results the scaling should be done before performing any other operations on it (crop, rotate, etc.). Note that if you make the image larger it may become fuzzy.

It’s always a good idea to maintain a copy of any images on your computer, but you do have the ability to revert any previous edits made to the image and restore the original image that you uploaded initially to your media library.