Perfectly Cromulent Image Cropping with the GIMP

24 August 2007

Make that extracromulent.

I’m guessing that most people with a digital camera or a web site have spent time cropping pictures. There are lots of programs that can do this. Often we start out by using the ones that happen to be installed, and we manage for better or worse with the functionality they happen to have. In this post I hope to show you that the GIMP is a great tool for cropping pictures. I’m sure Photoshop has similar abilities, but instead of paying $700 (or whatever it costs now), why not use the free GIMP, available for GNU/Linux, Windows, and the Mac.

Don’t limp along: get the GIMP.

The GIMP is the 800-pound gorilla of free software graphics programs. I love the GIMP, but at the same time am a little intimidated by it. (Much like I might feel about gorillas in general.) From the newbie point of view, using the GIMP for some jobs can seem like flying the space shuttle to the corner store to buy a gallon of milk. More power than you really need, and kind of bewildering with all the dials, buttons, and switches.

But I experiment. What do all these levers and switches do? If this thing can take me in to space, what can it do for ordinary jobs? And I slowly learn, and start firing up the GIMP for more and more jobs. I recently have been thrilled to discover the embiggeningness of the crop function in the GIMP. It’s really cool! So why not use it to get the mail from the box at the end of the driveway? It doesn’t use as much fuel as the space shuttle, after all.

With other programs I’ve used, cropping is serviceable. You make a free-hand selection with the mouse and may get some help with x and y coordinates for the mouse and a dynamic measurement of the height and width of your selection. It can be kind of tedious to get a precise selection size. Adjustments after selection can be impossible.

Viva la GIMP

There are a couple of different ways (at least) to crop in the GIMP. A more limited way is to use the rectangular select tool. In the window with your image, use menu Tools » Selection Tools » Rect Select, or shortcut key R. Free-hand select an area with the mouse, and then use menu Image » Crop Image.

Much better is to use the crop tool. Menu Tools » Transform Tools » Crop & Resize, or shortcut SHIFT + C. Your mouse pointer will turn in to cross hairs plus what looks like the tip of a scalpel (or some kind of cutting tool, anyway).

Then just click and drag a selection. A dialog box as shown below will immediately pop up, titled “Crop & Resize”. At the same time you’ll get guidelines shown in the screenshot here. You can continue dragging to select the area you’re interested in, but you’ll have plenty of options to get exactly the right area after you let go of the mouse button. (And you initially might have to stop and move the crop dialog out of the way.)

Before getting to the dialog options, you can do more free-hand operations by going to the corners of your selection. The upper-left and lower-right options let you resize your selection area. The other corners let you slide the selection around while maintaining its size.

As you can see in the dialog, you have plenty of fine-grain control over your selection. You can enter in exactly where you want the area to be and how big it should be. As an example related to my previous post about Paulo Barcello’s photography, I wanted to make a dual monitor wallpaper of the foreground in the City that Never Sleeps picture. With the Crop & Resize dialog, I entered in the width and height (2560 x 1024) to quickly get the precise size needed, and then moved the box around until I found the area I wanted to use.

Another way you can use this is if you want a certain ratio. If you take pictures on a camera that gives you 4:3 images (e.g. 1600×1200 pixels), you might want to crop them to a size suitable for printing out 3:2 ratio 6×4″ photos. If you give them “as is” to Wal-Mart, they’ll crop them for you with uncertain results. With this tool, you can pick the width of the image and then type 1.5 in the aspect ratio box. GIMP will calculate the necessary height, and now you can move your selection box around to pick the crop you want.

There remains some mystery in this dialog. Not sure what the From Selection and Auto shrink buttons are supposed to do. I can see that the Resize button does something, but don’t know how I’d use that either. I’ll bet those astronauts on the shuttle don’t know what all the controls do either.

One thing you’ll find with the GIMP is that it has plenty of “undo” power. It’s easy and safe to experiment. Check it out and see what you can do.

And now, cropped in the GIMP, here are some different wallpapers made from The City that Never Sleeps by Paulo Barcellos Jr. and made available under the Creative Commons Attribution ShareAlike 2.0 license.

2560 x 1024