Spline-based image registration

In a computer system, a method for extracting motion information from a sequence of images, comprising:

• storing a first set of light intensity values as a first image in a memory of the computer system;
• storing a second set of light intensity values as a second image in the memory;
• storing a plurality of control vertices in the memory as a data structure;
• associating the plurality of control vertices with the second image, each control vertex having a predetermined location with respect to the second image;
• adjusting the light intensity values of the second image to create a derived image, the adjusting being proportional to the distance between the control vertices and the light intensity values;
• determining a difference in light intensity values between the first image and the derived image;
• displacing each control vertex to a new predetermined location to minimize the difference between the first image and the derived image;
• and
• repeating the adjusting, determining, and displacing steps until the difference between the first image and the derived image is less than a predetermined amount, the locations of distorted control vertices stored in said memory characterizing the motion information of the first image and the second image.

An apparatus for extracting motion information from a sequence of images, comprising:

• a memory for storing a first image, a second image, and a plurality of control vertices associated with the second image, the first image, the second image, and the plurality of control vertices stored as data structures in the memory, the first and second images each expressed as a plurality of light intensity values, each light intensity value having a predetermined location, and the control vertices being expressed as coordinates relative to the locations of the light intensity values of the second image;
• means for transforming the second image to a derived image by adjusting each light intensity value of the second image by an amount proportional to a distance between the location of a particular light intensity value and a location of a corresponding control vertex;
• a comparator for determining a difference between the first image and the derived image;
• and
• means for adjusting the location of each of the plurality of control vertices to minimize the difference between the first image and the derived image, the adjusted locations of the control vertices parametrizing the motion information of the first image and the second image.

An apparatus for extracting motion information from a sequence of images, comprising:

• a memory storing a first image, a second image, and a plurality of control vertices associated with the second image, the first image, the second image, and the plurality of control vertices stored as data structures in the memory, the first and second images each expressed as a plurality of light intensity values, each light intensity value having a predetermined location, and the control vertices being expressed as coordinates relative to the locations of the light intensity values of the second image;
• means for transforming the second image to a derived image, the transformation adjusting each light intensity value of the second image by an amount proportional to a distance between the location of a particular light intensity value and a corresponding control vertex, the proportional amount expressed as a spline-function parametrized by the distance;
• a comparator for determining a difference between the first image and the derived image;
• and
• means for adjusting the location of each of the plurality of control vertices to minimize the difference between the first image and the derived image, the adjusted locations of the control vertices stored in said memory parametrizing the motion information of the first image and the second image.

A computer implemented method for extracting motion information from a sequence of images, comprising the steps of:

• storing a first physical image in a memory as a first set of light intensity values;
• storing a second physical image in said memory as a second set of light intensity values;
• defining, in said memory, a control grid for said first set of light intensity values, said control grid responsive to spline functions;
• distorting said control grid into a distorted control grid;
• interpreting the first set of light intensity values using said spline functions of said distorted control grid to generate a distorted set of light intensity values stored in said memory;
• comparing said distorted set of light intensity values with said second set of light intensity values to determine a difference;
• adjusting said distorted control grid to achieve a desired difference;
• using a final distorted control grid stored in said memory after said desired difference is achieved to characterize motion of the light intensity values from said first physical image to said second physical image.