Figure 8.27.  Eraser tool icon in the Toolbox

The Eraser is used to remove areas of color from the current layer or from a selection of this layer. If the Eraser is used on something that does not support transparency (a channel, a layer mask, or the Background layer if it lacks an alpha channel), then erasing will show the background color, as displayed in the Color Area of the Toolbox. Otherwise, erasing will produce either partial or full transparency, depending on the settings for the tool options.

If you need to erase some group of pixels completely, leaving no trace behind of their previous contents, you should check the "Hard edge" box in the Tool Options. Otherwise, sub-pixel brush placement will cause partial erasure at the edges of the brush-stroke, even if you use a hard-edged brush.

Tip

If you use GIMP with a tablet, you may find it convenient to treat the reverse end of the stylus as an eraser. To make this work, all you need to do is click the reverse end on the Eraser tool in the Toolbox. Because each end of the stylus is treated as a separate input device, and each input device has its own separate tool assignment, the reverse end will then continue to function as an Eraser as long as you don't select a different tool with it.

3.7.3. Tool Options

	Note
	See the Brush Tools Overview for a description of tool options that apply to many or all brush tools.

Figure 8.28.  Tool Options for the Eraser tool

See the Brush Tools Overview for a description of tool options that apply to many or all brush tools. The Eraser tool has only one special option (Anti-Erase), but the Opacity control is mentioned here as well because its name may be a bit confusing.

Opacity

The "Opacity" slider, in spite of its name, determines the "strength" of the tool. Thus, when you erase on a layer with an alpha channel, the higher the "opacity" you use, the more transparency you get!

Anti Erase

The Anti Erase option of the Erase tool can un-erase areas of an image, even if they are completely transparent. This feature only works when used on layers with an alpha channel. In addition to the checkbutton in the Tool Options, it can also be activated on-the-fly by holding down the Alt key (or, if the Alt key is trapped by the Window Manager, by holding down both Shift and Alt).

	Note
	To understand how anti-erasing is possible, you should realize that erasing (or cutting, for that matter) only affects the alpha channel, not the RGB channels that contain the image data. Even if the result is completely transparent, the RGB data is still there, you simply can't see it. Anti-erasing increases the alpha value so that you can see the RGB data once again.