The Scale Layer command resizes the layer
and its contents. The image loses some of its quality by being scaled.
The command displays a dialog where you can set parameters
concerning the size of the layer and the image quality.
Activating the Command
You can access this command from the image menubar through
Description of the “Scale Layer” Dialog
The “Scale Layer” dialog
When you enlarge a layer, GIMP has
to calculate new pixels from the existing ones. This procedure
is called “interpolation”. Please note that no
matter which interpolation algorithm is used, no new information
is added to the image by interpolation. If there are places in
the layer which have no details, you will not get any new ones
by scaling it. It is much more likely that the layer will look
somewhat blurred after scaling. Similarly, when you reduce a
layer, the image loses some of its quality when pixels are
The command displays a dialog which shows the dimensions
of the original layer in pixels. You can set the new
Height for the layer in the two text
boxes. If the adjacent chain icon is unbroken, the width
and height are automatically adjusted to hold their ratio
constant. If you break the chain by clicking on it, you
can set them separately, but this will result in
distorting the layer.
However, you do not have to set the dimensions in pixels.
You can choose different units from the drop-down menu. If
you choose percent as units, you can set the layer size
relative to its original size. You can also use physical
units, like inches or millimeters. However if you do that,
you should pay attention to the
X/Y resolution of the image.
If you enlarge a layer, the missing pixels are calculated
by interpolation, but no new details are added. The more
the layer is enlarged, and the more times it is enlarged,
the more blurred it becomes. The exact result of the
enlargement depends upon the interpolation method you
choose. After scaling, you can improve the result by using
the Sharpen filter,
but it is much better for you to use a high resolution
when scanning, taking digital photographs or producing
digital images by other means. It is an inherent
characteristic of raster images that they do not scale up
To change the size of the layer, GIMP
either has to add or remove pixels. The method it uses to do
this has a considerable impact on the quality of the result. You
can choose the method of interpolating the colors of the pixels
from the Interpolation drop-down menu.
No interpolation is used. Pixels are simply enlarged
or removed, as they are when zooming. This method is
low in quality, but very fast.
This method is a good compromise between speed and
This method takes a lot of time, but it produces the