Java Doc for WarpGrid.java in  » 6.0-JDK-Modules » Java-Advanced-Imaging » javax » media » jai » Java Source Code / Java DocumentationJava Source Code and Java Documentation

The mapping from destination pixels to source positions is described by bilinear interpolation within a rectilinear grid of points with known mappings.

Given a destination pixel coordinate (x, y) that lies within a cell having corners at (x0, y0), (x1, y0), (x0, y1) and (x1, y1), with source coordinates defined at each respective corner equal to (sx0, sy0), (sx1, sy1), (sx2, sy2) and (sx3, sy3), the source position (sx, sy) that maps onto (x, y) is given by the formulas:

 xfrac = (x - x0)/(x1 - x0)
 yfrac = (y - y0)/(y1 - y0)
 s = sx0 + (sx1 - sx0)*xfrac
 t = sy0 + (sy1 - sy0)*xfrac
 u = sx2 + (sx3 - sx2)*xfrac
 v = sy2 + (sy3 - sy2)*xfrac
 sx = s + (u - s)*yfrac
 sy = t + (v - t)*yfrac
 

In other words, the source x and y values are interpolated horizontally along the top and bottom edges of the grid cell, and the results are interpolated vertically:

 (x0, y0) ->            (x1, y0) ->
 (sx0, sy0)             (sx1, sy1)
 +------------+---------+
 |            |\        |
 |            | (s, t)  |
 |            |         |
 |            |         |
 |            |         |
 |            |         |
 | (x, y) ->  |         |
 |  (sx, sy)--+         |
 |            |         |
 |            |         |
 |            | (u, v)  |
 |            |/        |
 +------------+---------+
 (x0, y1) ->          (x1, y1) ->
 (sx2, sy2)           (sx3, sy3)
 

Points outside the bounds of the cells defining the grid warp will be mapped to the source image using the identity transformation.

WarpGrid is marked final so that it may be more easily inlined.

The grid is defined by a set of equal-sized cells. The grid starts at (xStart, yStart).

This method returns the value of pt in the following code snippet:

 float[] sxy = warpSparseRect((int)destPt.getX(), (int)destPt.getY(),
 2, 2, 1, 1, null);
 double wtRight  = destPt.getX() - (int)destPt.getX();
 double wtLeft   = 1.0 - wtRight;
 double wtBottom = destPt.getY() - (int)destPt.getY();
 double wtTop    = 1.0 - wtBottom;
 Point2D pt = (Point2D)destPt.clone();
 pt.setLocation((sxy[0]*wtLeft + sxy[2]*wtRight)*wtTop +
 (sxy[4]*wtLeft + sxy[6]*wtRight)*wtBottom,
 (sxy[1]*wtLeft + sxy[3]*wtRight)*wtTop +
 (sxy[5]*wtLeft + sxy[7]*wtRight)*wtBottom);
 

Points outside the bounds of the cells defining the grid warp will be mapped to the source image using the identity transformation.
Parameters:
  x - The minimum X coordinate of the destination region.
Parameters:
  y - The minimum Y coordinate of the destination region.
Parameters:
  width - The width of the destination region.
Parameters:
  height - The height of the destination region.
Parameters:
  periodX - The horizontal sampling period.
Parameters:
  periodY - The vertical sampling period.
Parameters:
  destRect - An int array containing at least2*((width+periodX-1)/periodX)*((height+periodY-1)/periodY)elements, or null.

The grid is defined by a set of equal-sized cells. The grid starts at (xStart, yStart). Each cell has width equal to xStep and height equal to yStep, and there are xNumCells cells horizontally and yNumCells cells vertically.

The local mapping within each cell is defined by the values in the table parameter. This parameter must contain 2*(xNumCells + 1)*(yNumCells + 1) values, which alternately contain the source X and Y coordinates to which each destination grid intersection point maps. The cells are enumerated in row-major order, that is, all the grid points along a row are enumerated first, then the grid points for the next row are enumerated, and so on.

As an example, suppose xNumCells is equal to 2 and yNumCells is equal 1. Then the order of the data in table would be:

 x00, y00, x10, y10, x20, y20, x01, y01, x11, y11, x21, y21
 

The grid is defined by a set of equal-sized cells. The grid starts at (xStart, yStart). Each cell has width equal to xStep and height equal to yStep, and there are xNumCells cells horizontally and yNumCells cells vertically.
Parameters:
  master - the Warp object used to initialize the griddisplacements.
Parameters:
  xStart - the minimum X coordinate of the grid.
Parameters:
  xStep - the horizontal spacing between grid cells.
Parameters:
  xNumCells - the number of grid cell columns.
Parameters:
  yStart - the minimum Y coordinate of the grid.
Parameters:
  yStep - the vertical spacing between grid cells.
Parameters:
  yNumCells - the number of grid cell rows.

This method returns the value of pt in the following code snippet:

 float[] sxy = warpSparseRect((int)destPt.getX(), (int)destPt.getY(),
 2, 2, 1, 1, null);
 double wtRight  = destPt.getX() - (int)destPt.getX();
 double wtLeft   = 1.0 - wtRight;
 double wtBottom = destPt.getY() - (int)destPt.getY();
 double wtTop    = 1.0 - wtBottom;
 Point2D pt = (Point2D)destPt.clone();
 pt.setLocation((sxy[0]*wtLeft + sxy[2]*wtRight)*wtTop +
 (sxy[4]*wtLeft + sxy[6]*wtRight)*wtBottom,
 (sxy[1]*wtLeft + sxy[3]*wtRight)*wtTop +
 (sxy[5]*wtLeft + sxy[7]*wtRight)*wtBottom);
 

Points outside the bounds of the cells defining the grid warp will be mapped to the source image using the identity transformation.
Parameters:
  x - The minimum X coordinate of the destination region.
Parameters:
  y - The minimum Y coordinate of the destination region.
Parameters:
  width - The width of the destination region.
Parameters:
  height - The height of the destination region.
Parameters:
  periodX - The horizontal sampling period.
Parameters:
  periodY - The vertical sampling period.
Parameters:
  destRect - An int array containing at least2*((width+periodX-1)/periodX)*((height+periodY-1)/periodY)elements, or null. If null, anew array will be constructed. a reference to the destRect parameter if it isnon-null, or a new int array of length2*width*height otherwise.
throws:
  ArrayBoundsException - if destRect is too small