image registration menu

Image registration means aligning two images with one another, using landmarks or features that are present in both images. A typical image registration problem would involve registering two maps that are differently scaled, so that the information in both maps could be combined in one image. Registration is a number-crunching operation that takes a long time when you register raster images. It is very fast, however, when you work with vector images.

The scheme for registration involves two images; one is called the master image, and the other is called the slave image. In the registration procedure, the master image is not modified, but serves as a model for the slave image. The slave image is modified so as to bring it into alignment with the master image. The procedure is as follows:

You select an image and click on the DISPLAY MASTER IMAGE menu field. The image you selected will be displayed. This is the master image.
You select another image and click on the DISPLAY SLAVE IMAGE menu field. The system displays the image. This is the slave image.
You click on the ADD REGISTRATION POINTS menu field. The system asks you to indicate a point in the master image. Click on some feature that also appears in the slave image. The system then asks you to indicate the corresponding point in the slave image. Do so. You have now created a registration point. The process continues until you click on button 2 or 3. If you don't like a registration point, click on the REMOVE POINT menu field and then click near the point you want to remove. To remove all the points, click on the REMOVE ALL POINTS menu field.
When you are satisfied with your registration points, click on the REGISTER SLAVE IMAGE menu field. The system will now make a new version of the slave image, warping it so as to bring the registration points into alignment with the corresponding points in the master image.

You can save a set of registration points in a disk file, which you can later recall and use again. To do so, enter the name you want for the registration file in the Reg. file menu field, and then click on the SAVE REGISTRATION menu field. To recall a saved registration, click on the RECALL REGISTRATION menu field.

When you click on REGISTER SLAVE IMAGE, a new version of the slave image is created. If you want to combine the master and slave images into one image that is big enough to hold both of them, you can do so by entering the composite image name in the Spliced image menu field, and clicking on SPLICE IMAGES. Note that the master and slave images must be of the same type for this to work. Also, only the first two registration points are used when splicing. No distortion is applied to the slave image, it is just scaled and rotated to make the registration points match. If you splice without specifying any registration points, the images will be overlaid without scaling or rotation. In this way, you can overlay vector images.

You can preview the effect of your registration by clicking on PREVIEW REGISTRATION. The system will ask you to indicate, in the master image, the area you want to preview. Do this with two clicks, just as if you were making a blowup. The system will display a blowup of the area you selected, then calculate the same view of the registered slave image, and display that.