Image Processing Toolbox

Point Mapping

The Image Processing Toolbox provides tools to support point mapping to determine the parameters of the transformation required to bring an image into alignment with another image. In point mapping, you pick points in a pair of images that identify the same feature or landmark in the images. Then, a spatial mapping is inferred from the positions of these control points.

Image registration using point mapping involves these steps:

1. Read the images into the MATLAB workspace.
2. Specify control point pairs in the images.
3. Save the control point pairs.
4. Fine tune the control points using cross-correlation. (This is an optional step.)
5. Specify the type of transformation to be used and infer its parameters from the control point pairs.
6. Transform the unregistered image to bring it into alignment.

This process is best understood by looking at an example. See Example: Registering to a Digital Orthophoto for an extended example.

Note    You may need to perform several iterations of this process, experimenting with different types of transformations, before you achieve a satisfactory result. In some cases, you may perform successive registrations, removing gross global distortions first, and then removing smaller local distortions in subsequent passes.

The following figure, Overview of Image Registration Process, provides a graphic illustration of this process.

Figure 5-1: Overview of Image Registration Process

Registering an Image

Example: Registering to a Digital Orthophoto