Image Processing Reference
In-Depth Information
In our example image, you have to preselect the eyes, otherwise the
reddish skin tone and the red objects in the photo would have been altered.
Select the Free Select tool ( Lasso ) in the Toolbox. Then go to the tools settings.
As a setting for Mode , select the second symbol from the left: Add to the current
selection . Now you can roughly draw around the eyes while holding the left
mouse button. Create four small selections in the picture. This localizes the
filter's operational sphere. Now apply the filter - voilà! Done.
As a last step you must, however, deselect your selection. Choose Select
> None . Optionally, you can isolate your selection with help of the Elliptical
Selection tool .
The Red Eye Removal filter didn't exist in versions of GIMP prior to 2.4. You
can use the method used before the Red Eye Removal filter was introduced if
the filter didn't have the desired effect. Here comes the description:
Use the Zoom tool to zoom in to the area of red in the eyes. It is important
that you select only the red section of the pupil.
Prepare the picture by dragging out at least two guides from the rulers.
Position them as tangents to the upper and left side of the pupil. Select the
Ellipse tool from the Toolbox. Point at the crossing point of the tangents. Click
and hold the left mouse button while dragging it diagonally from the top-
left corner of your imagined rectangle around the pupil toward the lower-
right corner of the rectangle. Now you have an ellipse around the pupil
that is marked by a border of “marching ants”. This defines the edge of your
selection. You can also use the Lasso tool. It is quicker and easier but also a
little imprecise.
You now have an active selection on your image. Your adjustments will
modify only the actively selected area; the remainder of the image is mask-
protected against changes
In this exercise, you want the selection to have a soft border, or feathering .
Without feathering, the adjustments you make will have a sharp-edged
border, and it will look as if someone cut out an object with a scissors and
pasted it on. Feathering the edges of the object will create a more natural
appearance. Use the Select > Feather menu item to access the feathering
function. The Feather Edges dialog pops up. Enter a value of 10 pixels and click
OK to accept your changes.
In the next step, remove the color saturation. Access the Colors >
Desaturate menu item. It requires only one click to remove the color levels
from your selected area. You should see only the gray values now.
Next, access the Colors > Brightness-Contrast menu item to correct the
brightness and contrast according to your taste. Finally, use the Select > None
menu item to deselect the area.
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