6. The Tools in the Toolbox / 6.3 Tools for Image Layers
6.3.15 Liquify 
Liquify
can be used to distort a picture by painting. You can use this tool to
convert a photo to a caricature or to correct facial expressions.
Liquify has several subtools:
- Push Left

- All
pixels are pushed to the left relative to the moving direction of the
brush. If you are painting from the top to the bottom, the pixels will be
pushed to the left, the other way round they will be pushed to the right.
You can use this to shift edges in a picture.
- Forward Warp

- The
pixels are pushed along the moving direction. Example: You can use
this to adjust the corners of a person's mouth to create a smile.
- Soften

- The
distortions are softened thus correcting too strong distortions locally.
- Reset

- Reset
clears the distortions and recreates the starting condition.
- Twirl

- Twirl
rotates the pixels around the center of the brush clockwise. By
holding Alt the pixels are rotated counter-clockwise.
- Pucker

- Pucker
moves the pixels towards the center of the brush. This can be
used to shrink items.
- Bloat

- Bloat
moves the pixels toward the edge of the brush. This can be used to
enlarge items.
Liquify allows you to display a grid. Using the grid makes it easier to
recognize too strong distortions. Of course this grid will not be visible in the
final result.
When using Liquify you should pay attention to a few points:
- Liquify is a lossless tool. If you are using it for the first time with an
image, a new layer will be created gathering all the distortions. The
original image will not be modified. This way you can enhance your
modifications later if needed.
- If you want to apply your corrections permanently, the easiest way is to
mark the original image and the liquify layer in the layer dialog and to
use the command Layer/Reduce to One Layer. This command is
accessible from the context menu of the layer dialog, too.
- You should always use a soft brush. The steps distance should be a value
between 5% and 10%.
- Always use a brush, that is large enough. A brush too small can create
ugly distortions at the brush edge. This is especially true for Push Left
and Forward Warp.
- If you are using a high tool intensity, a small wrong movement can
create a wrong distortion. Therefore it is often better to use a small
intensity and to apply the correction several times.
- Of course Liquify observes the mask. This way you can protect areas
from modification.