To use the Control Point Selection Tool, enter the
cpselect command at the MATLAB® prompt. As arguments, specify the image you want to register (the moving image)
and the image you want to compare it to (the fixed image).
cpselect command has other optional arguments. You can import
existing control points, so that you can use the Control Point Selection Tool to modify,
delete, or add to existing control points. For example, you can restart a control point
selection session by including a
cpstruct structure as the third argument.
For more information about restarting sessions, see Export Control Points to the Workspace.
For simplicity, this example uses the same image as the moving and the fixed image, and no prior control points are imported. To walk through an example of an actual registration, see Register an Aerial Photograph to a Digital Orthophoto.
moon_fixed = imread('moon.tif'); moon_moving = moon_fixed; cpselect(moon_moving, moon_fixed);
When the Control Point Selection Tool starts, it contains three primary components:
Details windows—The two windows displayed at the top of the tool are called the Detail windows. These windows show a close-up view of a portion of the images you are working with. The moving image is on the left and the fixed image is on the right.
Overview windows—The two windows displayed at the bottom of the tool are called the Overview windows. These windows show the images in their entirety, at the largest scale that fits the window. The moving image is on the left and the fixed image is on the right. You can control whether the Overview window appears by using the View menu.
Details rectangle—Superimposed on the images displayed in the two Overview windows is a rectangle, called the Detail rectangle. This rectangle controls the part of the image that is visible in the Detail window. By default, at startup, the detail rectangle covers one quarter of the entire image and is positioned over the center of the image. You can move the Detail rectangle to change the portion of the image displayed in the Detail windows.
The following figure shows these components of the Control Point Selection Tool.
The next step is to use navigation aids to explore the image, looking for visual elements shared by both images. For more information, see Find Visual Elements Common to Both Images.