When you work with an image that contains a selection or mask, you can use that information to control how the Liquify command adjusts the image. Think of the mask as a visual representation of the work areas of the image. Creating a mask gives you precise control over what portions of the image are modified.
Layers palette, and then select the layer containing a selection or mask.
Filters menu, and then click
Liquify .
Replace Selection. Shows the selection, mask, or transparency in the original image.
Add To Selection. Shows the mask in the original image, so you can then add to the selection using the Freeze tool.
Subtract From Selection. Subtracts pixels in channel from current freeze.
Intersect With Selection. Uses only pixels that are selected and currently frozen.
Invert Selection. Removes Image Information with Extract.
OK .