Method for warping first and second overlapping images includes selecting a first set of points in a first image, the first set of points being located in an overlap region between first and second images; selecting a set of tie points in the second image, including individual tie points each of which correlates to a point in the first set of points; selecting from the first image a patch including at least one point from the first set of points and at least one neighboring point; performing shadow detection to determine a percentage of the patch exceeding a predetermined percentage, thereby indicating a shadow; if so, eliminating the at least one point so that it is not correlated with any of the individual tie points, thereby avoiding correlating the shadow in the first image to a shadow in the second image.
1. A method for transforming image data representative of a set of overlapping images to produce an image mosaic, comprising:
selecting a first set of points in a first image, the first set of points being located in an overlap region between the first image and a second image;
selecting a set of tie points in the second image, the set of tie points comprising individual tie points, each individual tie point correlating to a point in the first set of points;
selecting a patch in the first image, the patch comprising patch points including at least one point from the first set of points and at least one neighboring point within a first distance from the at least one point;
performing shadow detection to determine a percentage of the patch comprising a shadow;
determining if the percentage of the patch comprising the shadow exceeds a predetermined percentage;
if the percentage exceeds the predetermined percentage, eliminating the at least one point from the first set of points so that the least one point is not correlated with any of the individual tie points, thereby avoiding correlating the shadow in the first image to a shadow in the second image; and
warping the first and second images together to produce the image mosaic, said warping not utilizing any points eliminated from the first set of points.
2. The method of claim 1 wherein performing shadow detection comprises:
establishing a shadow range;
creating a histogram from image data of the patch;
determining, from the histogram, whether a bimodal distribution exists for the patch;
if the bimodal distribution exists, determining from the image data a mean point intensity for the patch;
determining whether the mean point intensity value falls within the shadow range;
using the mean intensity value to determine the percentage.
3. The method of claim 2 wherein determining whether a bimodal distribution exists comprises calculating a bimodal coefficient.
4. The method of claim 1 , further comprising reducing the resolution of the patch by a resolution parameter.
5. The method of claim 4 , further comprising reducing the resolution of the second image by the resolution parameter.
6. The method of claim 1 , further comprising performing coarse mapping of the first image and the second image.
7. The method of claim 6 wherein performing coarse mapping comprises:
establishing a set of user correlations, the user correlations correlating the first set of points with the at least one set of tie points;
calculating a Delaunay triangulation of the at least one set of tie points; and
using the Delaunay triangulation to create an initial warp of the first image and the second image.
8. The method of claim 7 wherein using the Delaunay triangulation comprises computing a linear coarse warp, the linear coarse warp being used to create an initial warp of the first image and the second image.
9. A computer readable medium readable by a computer, the medium embodying a program of instructions executable by the computer to cause the computer to transform image data representative of a set of overlapping images to produce an image mosaic by performing the actions of:
selecting a first set of points in a first image, the first set of points being located in an overlap region between the first image and a second image;
determining a set of tie points in the second image, the set of tie points comprising individual tie points, each individual tie point correlating to a point in the first set of points;
selecting a patch in the first image, the patch comprising patch points including at least one point from the first set of points and at least one neighboring point within a first distance from the at least one point;
performing shadow detection to determine a percentage of the patch comprising a shadow;
determining if the percentage of the patch comprising the shadow exceeds a predetermined percentage;
if the percentage exceeds the predetermined percentage, eliminating the at least one point from the first set of points, the at least one point being an eliminated point, so that the eliminated point is not correlated with any of the individual tie points, thereby avoiding correlating the shadow in the first image to a shadow in the second image; and
warping the first and second images together to produce the image mosaic, said warping not utilizing any points eliminated from the first set of points.