How to Fix Photos with Free, Open Source Software

Friday Nov 22nd 2013 by Carla Schroder

Why pay for Photoshop when you can fix and enhance your digital photographs with GIMP? The high-end, open source photo editor and graphics program won’t cost you a cent.

Small business owners need great looking images on their websites and for their printed materials. If you want to make your images look their best, but you don’t want to spend a ton of money to do it, you've come to the right place. Read on.

One of the best open source graphics programs is called GIMP, which stands for GNU Image Manipulation Program (GNU refers to a whole ecosystem of free/open source software). GIMP runs on Mac, Linux, and Windows, and it's open source and free of cost. We'll go over different ways that you can edit your photos and images with GIMP.

Photo in need of red-eye removal

Figure 1: A nice photo of nice people with not-so-nice red-eye.

You can use GIMP to create original images or to edit photographs and images in nearly any image file format. It comes with a wealth of software "tools" such as brushes, pencils, airbrush, eraser, smudge, calligraphy, and a ton of special effects. It fully support Wacom drawing tablets, and if you haven't tried a Wacom tablet you're missing out, because it lets you draw with a stylus just like drawing on paper. And wonder of wonders, GIMP offers very good documentation, and you'll also find a number of excellent GIMP books, so you can always find out how to do what you want.

A quick reminder before we start: Before editing your precious photos, always make backup copies first.

Install and Get to Know GIMP

Visit GIMP's download page to find the installers for Mac and Windows. It's already included in most Linux distributions.

GIMP is a little overwhelming the first time you look at it, but that's the nature of image editing software: there are lots of cool things you can do with it. It's worth learning your way around GIMP, because it is so versatile and just plain fun.

When you open it the first time, the default view has three separate detached parts: the Toolbox-Tool Options dock, the Edit Window, and the Layers-Brushes dock. Some people like it this way. If you're more comfortable with a single-window view, you can have that too—just go to the Windows menu and click Single-Window Mode.

Note that the cursor changes according to where you place it. When you move it over the menus or toolboxes it changes to a normal cursor, and when you move it over an image in the edit window it changes to a tool. The default is the Paintbrush tool. If you accidentally make a mark with it, no worries because all you have to do is press Ctrl+z to undo, or use Edit > Undo.

How to Remove Red-eye

Figure 1 shows a photo of two wonderful people (hi Terry and Hap!), but unfortunately Terry has a bad case of red-eye, and she looks a tad possessed.

But no worries, because red-eye removal is a standard photo editing tool, and GIMP's works beautifully. First click the Ellipse Select tool from the top-left of the toolbox, or from the Tools menu. Then use it to select a region around your subject's eyes. It doesn't have to be precise, because GIMP will find the eyes with just a little help from you.

GIMP red-eye preview

Figure 2: GIMP's red-eye removal tool provides a live preview.

Note: If you're not familiar with image editing software, you might take a little time to practice using the Ellipse and Rectangle Select tools, because there is a knack to making them select what you want.

OK, back to Terry and Hap. Go to Filters > Enhance > Red-Eye Removal, and you'll see something like Figure 2. Note than the Red-Eye Removal tool has a slider that lets you adjust the intensity of the color change (threshold). You can preview it before applying it. When it looks right click OK.

Speaking of zoom tools, there is one at the bottom of the main edit window so you can zoom in on your photo and see what you're doing. If you don't like the prefab zoom values, you can type in whatever value you want.

Brush and Pencil Sizes

GIMP paint brushes options

Figure 3: GIMP's adjustable Paintbrush options.

GIMP's default size for Paintbrushes and the Pencil is 20. You can change this using the up-down arrows in the Brush Size controller, or by typing in a value, or by dragging the blue slider (Figure 3). You also have options for different levels of hardness, patterns, opacity, and a multitude of modes such as dodge, lighten, darken, and many more. All tools offer great option sets.

How to Save Your Work in GIMP

Save your files the same way you save them in any program, by using the File menu. File > Save As saves your images in the default GIMP file format, which is .xcf. This is not a standard image file format, but a special native GIMP format. Use the .xcf format as your master save format because it preserves layers, channels, paths, transparency, and other editing data. This allows you to go back and easily re-edit your images without having to start over, and without losing your editing options.

When you are finished editing, you then need to export your image to a standard format (File > Export) such as .jpg, .png, .gif, .psd, or .tiff. If you plan to use your images on the Web, .jpg and .gif work well because you get good image quality in the smallest file size. Another good Web format—.png—supports transparency (unlike .jpg). If you need very large file sizes for printing images or for high-quality archiving, go with .tiff file format.To learn more, Wikipedia's Image file formats is a good reference.

All About Image Cropping

Cropping photos is something more people really should do before making other people look at them. A bit of good cropping clears away cruft, adds drama, and draws the eye to the subject. Our brains fill in the missing parts because we already know what things look like, so it's not necessary to include everything in your photos. Figure 4 is a cute but mundane snapshot, and we can improve it by cropping out the boring background, and homing in on the subjects.

Cropping images in GIMP

Figure 4: A cute pic that's prime for cropping.

Select the Crop tool, which looks like an X-Acto knife, and use it to select the part of the image you want to keep. Like most of GIMP's tools, the crop tool is forgiving, and has corner handles so that you can tweak it until you have it just right. Then press the Enter or Return key to make the crop and, as always, if you don't like it you can undo it.

In fact, GIMP provides an Undo History in the right-hand dock; just look at top row of tabs for the one with the yellow undo arrow. You can use this to go directly to any point in your undo history, including all the way back to the beginning. Figure 5 shows the improved version.

The post-cropped image

Figure 5: The cropped—and improved—goat and bear.

This photo was taken on a gloomy wet day, so I brightened it with Colors > Brightness-Contrast. First I increased the contrast to brighten the colors and sharpen the image, and I kicked the brightness level up a bit to bring out the white a little more. Then I used the Smudge tool to blur out the cars in the background. As a general rule, when you want to make colors richer and images appear sharper try increasing the contrast first.

Resizing Images in GIMP

When you want to make images larger or smaller, go to Image > Scale Image. Note the little chain link to the right of the Width and Height settings; by default these are linked so that when you change one the other automatically changes to stay in proportion. If you want to control them separately, click the chain to un-link them. Don't make images larger unless you have no other option, because that magnifies pixels and the results usually look bad.

Printing Images

GIMP's printing dialog is pretty nice, and it allows you to make and preview all kinds of finicky adjustments without wasting ink and paper. You can set the paper type and size, color modes, number of copies, scaling, borders, and print borderless. You'll get the best results with an inkjet photo printer that uses separate ink cartridges for each color, such as black, cyan, magenta, and yellow, and by selecting the correct paper type.

You'll be a lot happier with GIMP if you refer to the good documentation. My favorite GIMP books are Beginning GIMP: From Novice to Professional, by Akkana Peck, and The Book of GIMP: A Complete Guide to Nearly Everything by Olivier Lecarme and Karine Delvare. Visit GIMP documentation for more documentation and how-tos.

Carla Schroder is the author of The Book of Audacity, Linux Cookbook, Linux Networking Cookbook,and hundreds of Linux how-to articles. She's the former managing editor of Linux Planet and Linux Today.

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