Gimp 2

This page will highlight and explain the curriculum offered in GIMP 2, Wednesday June 10th.

Working with Digital Photos

Rotate and Crop

From the first GIMP class we should be familiar with rotating and cropping tools. These two tools are very useful in righting skewed photos. While rotating, one good way to ensure a flat horizon is to drag a false horizon down from the ruler bar to line your photo against as you rotate.

The crop tool allows you to easily trim out a perfect square from the tilted picture.

Colors

Once you are satisfied with the remaining image, there are a few ways to improve the color richness and clarity. My favorite is adjusting the levels but there are many different ways to manipulate the image's color.

Adjusting the levels of light in your photographs manipulates the color levels in your photos and fixes any brightness/contrast issues. The tool to do that is found under the image menu item Colours>Levels. It brings up a "Levels" dialog box.

You can ask GIMP to automatically find the best levels for your digital photographs by pressing "Auto" in this box. You must click "Ok" to finalize the adjustments.

It is also possible to manually adjust the sliders or use the eyedroppers to find perfect black, white etc. Hover the mouse over the eyedropper icons to see what reading it will take.

For color photos you can adjust the Red, Green and Blue levels separately for more control. This is quite useful in under or over-exposed pictures.

Washed out images will often also benefit from more Saturation, found under the Hue/Saturation tool, and over-saturated photos can be lightened with the levels or with Brightness/Contrast.

Experiment with the various color tools, it is an easy way to really change the tone of a photo, and don't forget you can always undo it if you don't like the changes!

Foreground Select

This tool puts together a few other tools to make it easy to select and isolate a region of your picture to be designated "foreground."

It is a three-part tool:

First you are given the lasso, to draw a rough loop around what you want to capture.

Then the tool turns to a paintbrush. Use the brush to mark the foreground elements you want to capture. Make as many stokes as you want. Ensure that there are no highlighted bits left on your foreground. By changing the tool properties, you can designate if you are marking the foreground or the background, but foreground is default. It isn't a big problem if some of the background comes along, you can always erase it, but if some of the foreground is left behind you will have a spotty image. Once you are satisfied, hit Enter and your foreground will be selected!

You can then copy your selection to the clipboard and bring it to other photos, or paste it back onto your original image and make it into a new layer, so you can apply filters and effects to the background and foreground independently on separate layers.

Paths

The Paths tool uses Bezier curves to draw lines or shapes that can be used to draw on or select parts of your image.

A Path is made up of nodes. When you choose the Path tool and hover over the image, notice the small plus (+) sign next to the icon. Click and you will start setting nodes. Connect-the-dots to make the line or shape you like, and pull and tweak the lines to curve after you've set the nodes.

To create a whole shape, create all the nodes first, then hold down the Control key while clicking on the first node to connect them. You will know it will connect when the plus sign turns to an infinity sign.

Once the Path is drawn, you can use it to manipulate the image by creating a selection based on the path, or by choosing a paint tool to stroke the path.