The Scale Image function enlarges or reduces the image by changing the
number of pixels it contains. It changes the size of the image content and
resizes the canvas accordingly.
It acts on the whole image. If your image has layers with different sizes,
it is possible that making the image smaller will shrink some of them
completely away (a layer cannot be less than 1 pixel wide or high). If
this happens you will be warned before the operation is applied.
If you want to scale a particular layer only, use the function
Scale Layer.
Note
If scaling would produce an image larger than the "Maximum new image
size" set in the
Environment
page of the Preferences dialog, you are warned and asked to confirm that
you really want to do it. Saying yes will not necessarily have bad
consequences, but you should give it a moment of thought, because very
large images consume a lot of resources, and outrageously large images
may consume more resources than you have, causing GIMP to crash or
otherwise behave unpleasantly.
9.16.1.
Activate Dialog
This command can be accessed from an image menubar as
Image → Scale image.
9.16.2.
Scale Image Dialog
Figure 10.59.
The “Scale Image” dialog
Image Size
You must remember that an image can be located in four places: In
the image file, in the RAM after loading, on your screen when
displayed, on paper after printing. Scaling the image changes the
number of pixels (information) the image contains, so it directly
changes the amount of memory the image needs (in RAM or in a
file).
However print size depends also on the resolution of the image
(which basically says, how many pixels each inch on paper
contains). If you want to change printing size without scaling the
image and changing the number of pixels it consist of, you should
use the
Print Size dialog
. Screen size also depends not only on pixel number, but also on
the screen resolution, zoom factor and the
Dot for Dot
option.
Width; Height
When you launch the Scale function GIMP displays the
dimensions of the original image in pixels. You can set the
Width
and the
Height
you want to give to your image by adding or removing pixels.
If the adjacent Chain icon is intact, width and height keep
their proportion. If you break it by clicking on it, you can
set them separately: this will result in deforming the
image.
However you do not have to set dimensions in pixels, you can
choose different units from the drop down menu. If you
choose percent as units, you can set the image size
relatively to its original size. You can also use physical
units like inches or millimeters. However if you do that,
you should keep attention to the
X/Y resolution
fields (and set them to an appropriate value), because image
dimensions in pixels, which are being changed by this
dialog, are computed from physical units using these
resolution values.
If you are enlarging an image beyond its original size,
missing pixels are calculated by interpolation but no new
detail is added. The more enlarged the image is, the more
blurred it becomes. The exact result of enlarging depends on
the chosen interpolation method. You can improve the result
by using the filter
Sharpen
(after scaling) but the best method is to use a high
resolution when scanning, taking digital photographs or
producing digital images by other means. Not scaling up well
is an inherit nature of raster images.
Reducing your image may be necessary if you intend it to a
Web page. You have to take in account that most Internet
users have relatively small screens and that your big image
can't be completely displayed on them. Many of screens work
in 1024x768 or even smaller resolution.
Adding or removing pixels is called "Resampling".
X Resolution; Y Resolution
Here you can set the print resolution for the image.
Quality
The
Interpolation
drop down list provides a selection of available methods of
interpolating the color of pixels in a scaled image:
Interpolation Type
None
: no interpolation is used. Pixels are simply enlarged
or removed as they are when zooming. This method is low
quality, but very fast.
Linear
: this method is relativelly fast, but still provides
fairly good results.
Cubic
: The best, highest quality but also the slowest method
available.
![[Note]](../images/note.png)
