Class AffineTransformationBuilder

java.lang.Object
org.locationtech.jts.geom.util.AffineTransformationBuilder

public class AffineTransformationBuilder extends Object
Builds an AffineTransformation defined by a set of control vectors. A control vector consists of a source point and a destination point, which is the image of the source point under the desired transformation.

A transformation is well-defined by a set of three control vectors if and only if the source points are not collinear. (In particular, the degenerate situation where two or more source points are identical will not produce a well-defined transformation). A well-defined transformation exists and is unique. If the control vectors are not well-defined, the system of equations defining the transformation matrix entries is not solvable, and no transformation can be determined.

No such restriction applies to the destination points. However, if the destination points are collinear or non-unique, a non-invertible transformations will be generated.

This technique of recovering a transformation from its effect on known points is used in the Bilinear Interpolated Triangulation algorithm for warping planar surfaces.

  • Field Details

    • src0

      private Coordinate src0
    • src1

      private Coordinate src1
    • src2

      private Coordinate src2
    • dest0

      private Coordinate dest0
    • dest1

      private Coordinate dest1
    • dest2

      private Coordinate dest2
    • m00

      private double m00
    • m01

      private double m01
    • m02

      private double m02
    • m10

      private double m10
    • m11

      private double m11
    • m12

      private double m12
  • Constructor Details

    • AffineTransformationBuilder

      public AffineTransformationBuilder(Coordinate src0, Coordinate src1, Coordinate src2, Coordinate dest0, Coordinate dest1, Coordinate dest2)
      Constructs a new builder for the transformation defined by the given set of control point mappings.
      Parameters:
      src0 - a control point
      src1 - a control point
      src2 - a control point
      dest0 - the image of control point 0 under the required transformation
      dest1 - the image of control point 1 under the required transformation
      dest2 - the image of control point 2 under the required transformation
  • Method Details

    • getTransformation

      public AffineTransformation getTransformation()
      Computes the AffineTransformation determined by the control point mappings, or null if the control vectors do not determine a well-defined transformation.
      Returns:
      an affine transformation
    • compute

      private boolean compute()
      Computes the transformation matrix by solving the two systems of linear equations defined by the control point mappings, if this is possible.
      Returns:
      true if the transformation matrix is solvable
    • solve

      private double[] solve(double[] b)
      Solves the transformation matrix system of linear equations for the given right-hand side vector.
      Parameters:
      b - the vector for the right-hand side of the system
      Returns:
      the solution vector