This tutorial is based on Text and images Copyright © 2002 Seth Burgess. The original tutorial can be found in the Internet [TUT01].
This tutorial shows you how to draw straight lines with GIMP. Forcing a line to be straight is a convenient way to deal with the imprecision of a mouse or tablet, and to take advantage of the power of a computer to make things look neat and orderly. This tutorial doesn't use Straight Lines for complex tasks; its intended to show how you can use it to create quick and easy straight lines.
Create a New Image
First, create a new image. Any size will do. Use → to create a new image.
Choose a Tool
Select a paint tool from the Toolbox, for example the Pencil tool or the Paintbrush tool.
Create a Starting Point
Left-click in the image where you want a line to start or end. A single dot will appear on the screen. The size of this dot represents the current brush size, which you can change in the Brush Dialog (see Section 3.2, “Brushes Dialog”). Now hold down the Shift key on your keyboard, and keep it down.
Draw the Line
After you have a starting point and while pressing the Shift key, you will see a straight line that follows the cursor. Press the first button on the mouse (the leftmost one usually) and let it go. During that whole “click” of the mouse button, you need to keep the Shift key held down.
Final Result
You can draw straight lines with any of the Paint tools. The last step is to let go of the Shift key. We are finished. Some examples are shown in the next section.