Image Processing Reference
In-Depth Information
The cursor changes shape; it is now a paintbrush. In the second step, you
must inform the program which colors the object to extract has. Thus, you
paint over the entire surface of the foreground so that all possible colors
and shades are covered. Take care to stay inside the selected area when
painting. You can paint over the area to select in several steps. As soon
as you let go of the mouse button, the program begins to compute and
the surfaces that haven't been selected are covered. However, if not all
areas to select have been detected by the tool, you can paint the surfaces
again. They will be added to your first selection. If you accidentally
selected too much, you can switch the tool setting to Mark background
below Interactive refinement . Otherwise, you can simply hold the Ctrl key.
This way, you can select sections in your image that should be deleted
from the selection. The program recalculates the selection and creates a
new mask. You can refine the result again if you wish.
Figure 3.99
The foreground is painted over to cover
all shades and colors.
Finally, after you press the Enter key, the entire process is finished and a
real selection is created from the mask.
Perform the steps—selecting, painting over, pressing Enter—in one
go. Once you have begun working with the Foreground Select tool , it is not
possible to reverse any steps, neither with Undo History nor with Ctrl+Z .
The entire process appears as one work step in the Undo History once it is
completed. If you mess up somewhere in the process and you would like to
start again, simply select another tool in the Toolbox. The Foreground Select
tool is discontinued and you can start anew.
Nevertheless, corrections can be made during work as previously
described with the tool itself. When working with the paintbrush (step 2), you
can select a coarse brush to cover large surfaces. Afterward, the details can be
worked out with a smaller brush. The brush size can be selected in the tool
If you marked too much as foreground, you can switch the tool settings
to Mark background . In a way, this lets you erase the over-drawn selection.
Before we start to view the results of the tool in an image with low
contrast between foreground and background, I would like to give you an
overview of the tool settings. We will be looking at only the tool settings that
you are not acquainted with:
Contiguous : This feature is selected by default. It indicates that only
cohesive surfaces are selected with the paintbrush. If you deselect this
option, other areas in the image that are the same color will be selected
when you use the paintbrush. For example, if you selected a flower in a
field full of flowers, all similar flowers would be selected automatically.
Interactive refinement : The choices under Interactive refinement allow
you to alternately select colors from the foreground or background,
depending on what you want to add to your selection.
Figure 3.100
The mask around the selected basketball
Figure 3.101
The finished selection
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