Picasa's Basic Fixes help you fix common problems with your pictures.
Basic Fixes
Undo / Redo
Picasa never saves over your original files, so you'll never ruin or damage a picture by editing it. Picasa preserves your original photo as a digital negative, so every edit you make is fully undoable. If you want to work with your edited pictures in other programs, you should export or save a copy of them.
Saving Pictures
To save a version of your edited picture, choose File>Save a Copy, or use Picasa's Export to Folder tool.
Pan / Zoom
The Pan/Zoom slider is located in the bottom right of your screen. To zoom into a picture, drag the zoom slider to the right, or hold the up arrow key. When you are zoomed in, the Zoom window will appear. To pan around inside the picture, click and drag inside the Zoom window.
To zoom out, click the Fit button or hit Escape to exit. Click the 1:1 button to view a picture at its actual resolution onscreen.
Rotate
To rotate a single picture, click on the picture you want to rotate, and click the Rotate arrow. To rotate multiple pictures, shift+click or control+click to select multiple pictures, and click the Rotate arrow. If your digital camera supports auto rotate, Picasa will automatically orient your pictures correctly.
You can use ctrl+R to rotate clockwise or ctrl+shift+R to rotate counterclockwise.
Histogram & Camera Information
A real-time histogram that displays advanced EXIF information and RGB color values and intensity.
(For the hard-core photography experts.)