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Use Cross-Correlation to Improve Control Point Placement

You can fine-tune the 2-D control points you selected using cpselect. Using cross-correlation, you can sometimes improve the points you selected by eye using the Control Point Selection Tool.

To use cross-correlation, pass sets of control points in the moving and fixed images, along with the images themselves, to the cpcorr function.

moving_pts_adj = cpcorr(movingPoints,fixedPoints,moving,fixed);

The cpcorr function defines 11-by-11 pixel regions around each control point in the moving image and around the matching control point in the fixed image. The function then calculates the correlation between the values at each pixel in the region. Next, the cpcorr function finds the position with the highest correlation value and uses it as the optimal position of the control point. The function only moves control points up to four pixels based on the results of the cross-correlation.


Features in the two images must be at the same scale and have the same orientation. They cannot be rotated relative to each other.

If cpcorr cannot correlate some of the control points, it returns their unmodified values in movingPoints.

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