GooEdit adds a basic image editor to Google Chrome
GooEdit offers a good array of tools. Images can be rotated, flipped, and cropped and color adjustment tools like brightness/contrast and histogram are included. A few effects are available, too, like grayscale, sepia, solarize, and invert. GooEdit can even add or remove noise, sharpen, or blur your selected image.
To launch the editor, simply hold down your alt key and click an image with your right mouse button. When you're all finished, click the disk icon to save and your handiwork is loaded in a new tab -- where you can right-click to save or copy it.
What GooEdit lacks are annotation features (like text and shape tools) and sharing options (though plenty of extensions can already handle this task for you). Hopefully those will be added in future, because they'd make GooEdit even more useful than it already is.