GIMP Bible

Chapter 7. Using Channels

IN THIS CHAPTER

• Discovering what channels are

• Taking advantage of channels to enhance images

In most image editing applications, the channels feature is usually the most misunderstood and underutilized tool in the kit. Part of this has to do with the fact that most image formats are flattened and the only channels that they have available to them are red, green, and blue. Although these channels can be very helpful in tweaking your image's colors, there's much more to channels than the component colors that make up the image. This is especially true in a powerful image editor like GIMP.

The purpose of this chapter is to introduce you to channels and demonstrate all of the cool ways that they can be used to enhance your digital images. You see how they can not only give you precise control of colors, but how to use them in GIMP to create and store selections, enhance the contrast in black-and-white images, and control the overall transparency of your final output.

Understanding Channels

The fastest way to see and control channels in GIMP is through the Channels dockable dialog, shown in Figure 7-1. By default, it's the second tab after the Layers dialog and it shares a number of the same interface paradigms. It has a large central panel that displays a list of elements and a series of buttons beneath this panel.

On a typical flat image format like JPEG or PNG, you will see three or four separate channels: Red, Green, Blue, and possibly Alpha, if the image format ...