When most of us are looking for a photo-editing tool, we immediately think of Photoshop. Adobe's program is powerful and popular, but it's pricey at $100--and that's for the "light" version called Photoshop Elements.
Meanwhile, $20 per month is the standard charge for individual one-app subscriptions to Photoshop Creative Cloud. Adobe offers a free in-browser version called Photoshop Express Editor, but it's very limited and only allows you to edit JPEG files.
A better free alternative is to turn to the open-source world and a popular program called GIMP. The GNU Image Manipulation Program is the standard photo-editing tool included or available to most Linux distributions. GIMP is also available for Windows (XP and up) and Mac.
While photo-editing professionals may sneer at GIMP, the program has more than enough capabilities for the average person editing snapshots at home. Here are three basic tasks you can do with GIMP to get you started.
Cropping is simple to do in GIMP. In our example, we want to create a new photo that is a close-up of the animal in the image above.
First we open the Toolbox bar. You should see a long, thin window similar to what you see in Photoshop with your basic tool set. If you don't see it, go the menu bar and select Windows>Toolbox or just hit Ctrl-B.
Next, select the icon that looks like a dotted rectangle pattern, at the very top of the toolbox. Cropping is as simple as selecting the area by clicking and dragging your mouse.
Once that's done, go the menu bar and select Edit>Copy (or hit Ctl-C). Next, select File>Create>From Clipboard and voilà: We have our cropped image.
Copy and Undo
One of the best features of GIMP is that it's very forgiving of mistakes. Similar to other desktop programs, GIMP lets you undo multiple changes by tapping Ctrl-Z on your keyboard. If you need more specific undo access, you can also work with the undo history dialog by selecting Windows>Dockable Dialogs>Undo History.
Although GIMP is very forgiving, it's still a good idea to duplicate any images you're going to edit heavily. That way, you always have a fallback copy of the original photo. To copy, just tap Ctrl-D on your keyboard, and a new copy of your image will appear in its own window. Remember to save the new copy before you start playing.
Going black and white
There are several ways you can change a color image to black-and-white in GIMP. For me, the easiest and most effective mode is to use the desaturate option.
Open an image and copy it as described above (keep the original handy!).
Next, from the menu bar select Colors>Desaturate. Your image will immediately go to black-and-white, and you'll see a smaller second window appear with three options: Lightness, Luminosity, and Average. You can select only one, and each option slightly changes the look of the image.
Choose an option, hit OK, then save your new image.
A word about saving and file types
By default, GIMP for Windows and Linux saves all your images as XCF files. If you're creating something for the web where the image needs to be saved in a .JPG or .PNG format, you don't want to save your image. Instead, you want to choose File>Export as... and then choose the desired file type in the save dialog window.
A new copy of the image will be saved, and the version you're still looking at will be unchanged. If you don't want to keep the XCF version, just close the window and select Discard Changes. The saved JPG or PNG file will still be there.
Moving to GIMP from Photoshop may take some adjustment. If you ever need any help, there's also a great set of documentation on the GIMP project site.