'Cropping' means
trimming the edges off a picture. This is such a basic and
straightforward operation that you might be wondering why I
did not include it in the previous lesson, 'Corrections'.
This is because cropping is often deliberately used to
change the impression given by a picture, and that is much
more than just correcting faults within the picture. As an
example, look at the picture below...
I think the picture would be better without the people,
since it would give the impression that the elephants are
wild (which they are not, for I took this picture in an
elephant reserve in Phuket, Thailand).
Here are three ways to crop the picture:
First, the official way, using the crop tool
.
Once the crop tool is selected, drag to create a
selection rectangle that includes the elephants and as much
water as possible but none of
the people. If the rectangle that you have created is not
quite right then you can use the mouse to pull the 'handles'
in the top-left or bottom-right corners of the rectangle to change
its size or pull the handles in the top-right or bottom-left
corners to change the position of the rectangle. You can also drag the whole rectangle into a new
position by dragging any part of the selection except the
handles. When you are satisfied with the selection then
click the Crop button or simply click inside the cropping
rectangle (or Escape if you made a
mistake with the selection and wish to try again). Save your
work before continuing.
A very common problem in photographs is that the
photograph is slanted because the camera was not held
exactly horizontal or vertical when the photograph was taken
(see the example below, taken in Tahiti). In order to solve
this problem the image must first be rotated and then
cropped. In the GIMP, choose the rotation tool
or
Layer>Transform>Arbitrary Rotation or just Shift+R.
First, set the options for this tool to include Transform
direction: forward and Preview: image and then try rotating
the image. It works OK, in an intuitive way, but there's a
problem: it's hard to know when you have rotated the image
the right amount. So press the Escape key to abandon what
you were doing and try again with these new settings:
Transform direction: backward and Preview: grid. Now you
have to twist in the opposite direction until the grid lines
up with the horizon - a little counter-intuitive but
ultimately better since it allows you to be sure you have
the correct adjustment. Press Enter to finalize the
rotation, then use the cropping tool to crop the picture,
then save your work.
An alternative way to crop images is to resize the canvas
(Image>Canvas Size) to a size smaller than the
current size.
