Displace

The Displace transformation lets you distort an image in a variety of ways. The most interesting effects are obtained when the distortion is controlled by one or two black and white images.

There are two methods of distortion supported: Rectangular and Circular. If you choose Rectangular, then each pixel in the output image is derived by sampling the input image at a location displaced from the output pixel by horizontal and vertical offsets. If you select Circular, then the offsets are applied as magnifications and rotations rather than horizontal and vertical shifts. The magnitude of the offsets is determined by the Amount slider and the Horizontal and Vertical (or Magnification and Rotation) sliders.

Amount

The amount control lets you control how much distortion is applied to the input image. You can apply a percentage of the transformation to the entire image, or you can specify an amount mask to restrict the effects of the transformation to only part of the input image. The Amount you select acts like a scale factor which is applied to the offsets specified by the other two sliders.

Method

The method setting can be set to Rectangular or Circular.

Rectangular -- distortion will be based on shifting the input image horizontally and/or vertically. In this case the two sliders at the bottom of the dialog box will be labeled Horizontal Shift and Vertical Shift.

Circular -- distortion will be based on rotations or magnifications and/or the input image with respect to its center. In this case the two sliders at the bottom of the dialog box will be labeled Magnification and Rotation.

If you specify constant amounts for the offsets, the image is simply shifted (or rotated and magnified). However, by selecting masks into any of these controls, the displacements can be made to vary from one part of the image to another, thus creating distortion effects.

Tile

If tiling is off, when offsets result in a location outside the image, the background color is substituted. If tiling is on, the location wraps around from one side to the other and from the top to the bottom.

Background Color

The background color specifies the color of pixels that fall outside of the input image. If the input image is black and white, the luminance of the background color is used. If you need a color instead, first convert the input image to a color image.

The Texture and Gradient transformations are particularly useful in creating displacement masks.