Registration: Manual 2D Series

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Registration: Manual 2D Series

The Manual 2D Series algorithm allows you to manually or semimanually register two 2D grayscale or color images by placing corresponding points on both images and then applying either the Landmark-Thin Plate Spline or Landmark-Least Squares algorithm. After applying one of these algorithms, you can then, if needed, use the other algorithm. In addition, at any time, you can manually adjust the alignment of each image.

The algorithm also lets you manually register different slices of a 2.5 image dataset in the same way as the 2D images.

Background

Through the Registration: Manual 2D Series window (Figure 1), this algorithm provides the tools for manually registering images and the ability to use two of the landmark registration algorithms. The Registration: Manual 2D Series window includes two tabs: Blended and Dual.

Figure 1. Registration: Manual 2D Series window

File:WindowManual2D.gif

On the Blended page, the window superimposes the image to be registered on top of the reference image. This page includes icons for aligning, rotating, alphablending, and magnifying or minifying the images as well as icons for modifying the lookup table for each image and for applying a checkerboard pattern to assist in alignment.

Clicking the Dual tab opens the Dual page, which displays the images side by side. A number of icons appear in the toolbar. The red icons are color coded to the reference image, which appears on the left and is surrounded by a red border. The green icons apply to the image to be registered, which is shown on the right side of the page and is surrounded by a green border.

Before being able to use either the Thin Plate Spline or Least Squares algorithm, you must first delineate a minimum of three corresponding points on both images. These points serve as guides, or landmarks, for aligning the images. In order for the points to be corresponding, you should delineate each point in the same sequence; i.e., the first point that you delineate on the reference image should be the first point delineated on the image to be registered, the second point on the reference image should be the second point delineated on the image to be registered, and so on.

To delete a point, you must first select the point and then use the appropriate Delete icon to delete it. However, before you can select the point, you need to return the cursor to its default mode using the icon.

On both the Blended and Dual pages, you can modify the lookup table (LUT) by clicking , the LUT icon. When you select , the Lookup Table window appears. This window includes two tabbed pages: one for Image A, the reference image, and one for Image B, the image to be registered.

A common icon- , the Reset icon-appears on both the Blended and Dual pages. Use this icon if you want to restore the original version of the images. This icon deletes all points on the reference image and on the image to be registered.

Note: If the Apply button has already been selected, the Reset icon undoes all changes that occurred since the last time the Apply button was selected.

Image types

You can apply this algorithm to 2D grayscale and color images.

The dimensions or image type of the image to be registered need not be the same as the dimensions or image type of the reference image. The registered image has the same image type as the image to be registered and the same extents as the reference image.

Special notes

The following notes apply:

For 2D images, three or more points are required. The algorithm may fail if nearly all of the points fall on the same line.

For 3D images, four or more points are required and the algorithm may fail if the points nearly all fall on the same plane.

References

Refer to the following references for more information:

"Least-Squares Fitting of Two 3-D Point Sets" by K.S. Arun, T.S. Huang, and S.D. Blostein, IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. PAMI-9, No. 5, September, 1987, pp. 698-700.

David Eberly, "Thin Plate Splines" of Magic Software at http://www.magic-software.com. Also at the same site are the files: MgcInterp2DThinPlateSpline.h, MgcInterp2DThinPlateSpline.cpp, MgcInterp3DThinPlateSpline.h, MgcInterp3DThinPlateSpline.cpp Paper that explains warping from one x,y source to another x,y target set.

Fred L. BookStein, "Principal Warps: Thin-Plate Splines and the Decompositions of Deformations," IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 11, No. 6, June 1989, pp. 567-585.

Applying the Manual 2D Series algorithm on 2D images

To run this algorithm, complete the following steps:

1 Open two images: the reference image and the image that you want to register.

2 Select the reference image.

3 Select Algorithms > Registration > Manual 2D Series. The Load dialog box appears.

Figure 2. The Load dialog box

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