linedx.java

实现二维基本图元直线段生成的基本算法（DDA

package graphics0;

import java.awt.*;

/**
 * <p>Title: computer graphics </p>
 * <p>Description: homeworks</p>
 * <p>Copyright: Copyright (c) 2004 </p>
 * <p>Company: shu</p>
 * @author dxf
 * @version 1.0
 */

public class LineDx
    extends Object2D {
  Point spoint, epoint;
  int DrawMethod;

  void drawDemo(Graphics Canvas) {
    Point tmp;
    switch (DrawMethod) {
      case 0: { //linedda
        if (Math.abs(spoint.x - epoint.x) > Math.abs(spoint.y - epoint.y)) {
          if (spoint.x > epoint.x) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }
          LineDDAXDemo(spoint.x, spoint.y, epoint.x, epoint.y, Canvas);

        }
        else {
          if (spoint.y > epoint.y) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }
          LineDDAYDemo(spoint.x, spoint.y, epoint.x, epoint.y, Canvas);
        }
        break;
      }

      case 1: { //mid
        if (Math.abs(spoint.x - epoint.x) > Math.abs(spoint.y - epoint.y)) {
          if (spoint.x > epoint.x) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }

          MidpointineXDemo(spoint.x, spoint.y, epoint.x, epoint.y, Canvas);
        }
        else {
          if (spoint.y > epoint.y) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }

          MidpointineYDemo(spoint.x, spoint.y, epoint.x, epoint.y, Canvas);
          break;
        }

      }
      case 2: { //Bresenham
        if (Math.abs(spoint.x - epoint.x) > Math.abs(spoint.y - epoint.y)) {
          if (spoint.x > epoint.x) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }

          InterBresenhamlineXDemo(spoint.x, spoint.y, epoint.x, epoint.y,
                                  Canvas);
        }
        else {
          if (spoint.y > epoint.y) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }

          InterBresenhamlineYDemo(spoint.x, spoint.y, epoint.x, epoint.y,
                                  Canvas);
          break;
        }

      }

    }

  }

////////////////////////////////////////////////////////////////////////////////
  void draw(Graphics Canvas) {
    Point tmp;
    int w1, w2, w;
    //////////////////////////////////////
    w = LineWidth % 2;
    if (1 == w) {
      w1 = (LineWidth + 1) / 2;
      w2 = 0 - (LineWidth - 1) / 2;
    }
    else {
      w1 = LineWidth / 2;
      w2 = 0 - w1;
    }

    switch (DrawMethod) {
      case 0: { //linedda
        if (Math.abs(spoint.x - epoint.x) > Math.abs(spoint.y - epoint.y)) {
          if (spoint.x > epoint.x) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }
          LineDDAX(spoint.x, spoint.y, epoint.x, epoint.y, Canvas,
                   w1, w2);

        }
        else {
          if (spoint.y > epoint.y) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }
          LineDDAY(spoint.x, spoint.y, epoint.x, epoint.y, Canvas,
                   w1, w2);
        }
        break;
      }

      case 1: { //mid
        if (Math.abs(spoint.x - epoint.x) > Math.abs(spoint.y - epoint.y)) {
          if (spoint.x > epoint.x) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }

          MidpointineX(spoint.x, spoint.y, epoint.x, epoint.y,
                       Canvas, w1, w2);
        }
        else {
          if (spoint.y > epoint.y) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }

          MidpointineY(spoint.x, spoint.y, epoint.x, epoint.y,
                       Canvas, w1, w2);
          break;
        }

      }
      case 2: { //Bresenham
        if (Math.abs(spoint.x - epoint.x) > Math.abs(spoint.y - epoint.y)) {
          if (spoint.x > epoint.x) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }

          InterBresenhamlineX(spoint.x, spoint.y, epoint.x, epoint.y,
                              Canvas, w1, w2);
        }
        else {
          if (spoint.y > epoint.y) {
            tmp = new Point(epoint);
            epoint = spoint;
            spoint = tmp;
          }

          InterBresenhamlineY(spoint.x, spoint.y, epoint.x, epoint.y,
                              Canvas, w1, w2);
          break;
        }

      }

    }
  }

  boolean IsInside(Point p0) {
    return (true);
  };

  public LineDx() {
    spoint = new Point(0, 0);
    epoint = new Point(0, 0);
    DrawMethod = 0;
  }

  public LineDx(Point s, Point e, int d, Color c, int w, int l) {
    spoint = new Point(s);
    epoint = new Point(e);
    ForeColor = c;
    DrawMethod = d;
    LineWidth = w;
    LineStyle = l;
  }

//////////////////////////////////////////////////////////////////////////////
  public void LineDDAX(int x0, int y0, int x1, int y1,
                       Graphics g, int w1, int w2)
  /* 假定x0<x1,-1<=k<=1 */
  {
    int x, t, w, j = 0;
    float dx, dy, y, k;
    g.setColor(ForeColor);
    dx = x1 - x0;
    dy = y1 - y0;
    k = dy / dx;
    y = y0;
    ////////////////////////////////////
    for (x = x0; x <= x1; x++) {
      t = Math.round(y);
      if (j == 8) {
        j = 0;
      }
      if ('1' == sLineStyle[LineStyle].charAt(j)) {
        for (w = w2; w < w1; w++) {
          g.drawLine(x, t + w, x, t + w);
        }
      }
      j++;
      y += k;
    }
  }

///////////////////////////////////////////////////////////////////////////////
  public void LineDDAY(int x0, int y0, int x1, int y1,
                       Graphics g, int w1, int w2)
  /* 假定-1<=1/k<=1 */
  {
    int y, t, w, j = 0;
    float dx, dy, x, k;
    g.setColor(ForeColor);
    dx = x1 - x0;
    dy = y1 - y0;
    k = dx / dy;
    x = x0;

    //////////////////////////////////////////////////
    for (y = y0; y <= y1; y++) {
      t = Math.round(x);
      if (j == 8) {
        j = 0;
      }
      if ('1' == sLineStyle[LineStyle].charAt(j)) {
        for (w = w2; w < w1; w++) {
          g.drawLine(t + w, y, t + w, y);
        }
      }
      j++;
      x += k;
    }
  }

////////////////////////////////////////////////////////////////////////////
  public void MidpointineX(int x0, int y0, int x1, int y1,
                           Graphics g, int w1, int w2) {
    int a, b, d1, d2, d, x, y, w, j = 1;
    g.setColor(ForeColor);
    boolean bg;
    if (y1 > y0) {
      bg = false;
    }
    else {
      bg = true;

    }
    if (bg) {
      a = y1 - y0;
    }
    else {
      a = y0 - y1;

    }
    b = x0 - x1;
    d = 2 * a - b;
    d2 = 2 * (a - b);
    d1 = 2 * a;
    x = x0;
    y = y0;
    g.drawLine(x, y, x, y);

    while (x < x1) {
      x++;
      if (d < 0) {
        if (bg) {
          y--;
        }
        else {
          y++;
        }
        d += d2;
      }
      else {
        d += d1;
      }
      if (j == 8) {
        j = 0;
      }
      if ('1' == sLineStyle[LineStyle].charAt(j)) {
        for (w = w2; w < w1; w++) {
          g.drawLine(x, y + w, x, y + w);
        }
      }
      j++;
    }
    /* while */
  }
  /* mid pointine */

  ////////////////////////////////////////////////////////////////////////////
  public void MidpointineY(int x0, int y0, int x1, int y1,
                           Graphics g, int w1, int w2) {
    int a, b, d1, d2, d, x, y, j = 1;
    g.setColor(ForeColor);
    boolean bg;
    if (x1 > x0) {
      bg = false;
    }
    else {
      bg = true;

    }
    if (bg) {
      a = x1 - x0;
    }
    else {
      a = x0 - x1;

    }
    b = y0 - y1;
    d = 2 * a - b;
    d2 = 2 * (a - b);
    d1 = 2 * a;
    x = x0;
    y = y0;
    g.drawLine(x, y, x, y);

    while (y < y1) {
      y++;
      if (d < 0) {
        if (bg) {
          x--;
        }
        else {
          x++;
        }
        d += d2;
      }
      else {
        d += d1;
      }
      if (j == 8) {
        j = 0;
      }
      if ('1' == sLineStyle[LineStyle].charAt(j)) {
        for (int w = w2; w < w1; w++) {
          g.drawLine(x + w, y, x + w, y);
        }
      }
      j++;

    }