/****************************************************************************
** Twin.java - aid transform from real 2d coordinte system to pixels and back
** Copyright (C) 1996  Ray L. Ewbank
**     
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
** 
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU General Public License for more details.
**   
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
**
** Direct any questions concerning this piece of Software to:
**
**   Ray L. Ewbank
**   29-02 Arlington Road
**   Woburn, MA  01801
**
**   (617) 938-7137
**
**   ewbank@gis.net
****************************************************************************
** Sets up for transforming from a real 2d coordinate system to a pixel
** coordinate system and back.
**
** Set xmin,xmax,ymin,ymax of the window, and set the number of points
** in x and y, and an optionally an (x,y) point offset.
**
** The x-unit per pixel is always equal to the y-unit per pixel.
** The mid-points of (xmin,xmax) and (ymin,ymax) are made to fall
** exactly on the middle pixel.  The "actual" (xmin,xmax) and (ymin,ymax)
** are adjusted accordingly to meet these criteria.
**
** The "middle" pixel is like 0 in the following scenarios:
**   n = 3,   -1  0  1
**   n = 4,   -2 -1  0  1
**   n = 5,   -2 -1  0  1  2
**   n = 6,   -3 -2 -1  0  1  2
**   ...
**
** The four transform() member functions convert from real coordinates to
** pixel coordinates or back.
**
** Whenever you change anything, everything is recomputed.  This is
** unfortunate with respect to efficiency, since you have to make several
** function calls to get everything set up right.  But how often are you
** going to set this up anyway? :)
*/
import java.awt.*;

class Twin {
  int w, h;
  int iofs, jofs;
  double xmin, xmax, ymin, ymax;
  double sxmin, sxmax, symin, symax;
  double dx, xdel, ydel;
  Twin() {
    w = h = 3;
    iofs=jofs=0;
    xmin = sxmin = -1.0;
    xmax = sxmax =  1.0;
    ymin = symin = -1.0;
    ymax = symax =  1.0;
    dx = 1.0;
    xdel = 2.0;
    ydel = 2.0;
  }
  void scale(double scalefactor) {
    double xmid = (sxmin + sxmax)/2.0;
    double ymid = (symin + symax)/2.0;
    double txdel = 0.5*(sxmax-sxmin)*scalefactor;
    double tydel = 0.5*(symax-symin)*scalefactor;
    sxmin = xmid-txdel;
    sxmax = xmid+txdel;
    symin = ymid-tydel;
    symax = ymid+tydel;
    adjustParameters();
  } 
  void setDimension(int inw, int inh) {
    w=inw; h=inh;
    adjustParameters();
  }
  void setDimension(Dimension in) {
    setDimension(in.width,in.height);
  }
  void setOffset(int inx, int iny) {
    iofs = inx; jofs = iny;
  }
  void setOffset(Point in) {
    setOffset(in.x,in.y);
  }
  boolean isIn(double x, double y) {
    return (x >= xmin && x <= xmax && y >= ymin && y <= ymax);
  }
  boolean isIn(Point2d p) {
    return isIn(p.x,p.y);
  }
  void adjustDx() {
    double xmid = (sxmin+sxmax)/2.0;
    int imid = w>>1;
    xmin = xmid - imid*dx;
    xmax = xmid + (w-imid-1)*dx;
    double ymid = (symin+symax)/2.0;
    int jmid = h>>1;
    ymin = ymid - jmid*dx;  
    ymax = ymid + (h-jmid-1)*dx;
  }
  void adjustParameters() {
    xdel = sxmax-sxmin;
    ydel = symax-symin;
    if (xdel/w > ydel/h)
      dx = xdel/(w-1);
    else
      dx = ydel/(h-1);
    adjustDx();
    xdel = xmax-xmin;
    ydel = ymax-ymin;
  }
  void setWindow(double x0,double y0, double x1, double y1) {
    sxmin = x0; symin = y0;
    sxmax = x1; symax = y1;
    adjustParameters();
  }
  Point transform(double x, double y) {
    return new Point(iofs+   (int)((x-xmin)/dx+0.5),
                     jofs+(h-(int)((y-ymin)/dx+0.5)));
  }
  Point transform(Point2d p) {
    return transform(p.x,p.y);
  }
  Point2d transform(int x, int y) {
    return new Point2d((x-iofs)*dx+xmin,(h-(y-jofs))*dx+ymin);
  }
  Point2d transform(Point in) {
    return transform(in.x,in.y);
  }
}