/// <summary>
/// 对当前输入的直线，在直线列表中创建图元，并画出来
/// </summary>
/// <param name="pStart">直线起点</param>
/// <param name="pEnd">直线终点</param>
/// <param name="color">直线颜色</param>
/// <param name="name">直线的名称</param>
public void drawLine_Bresenham(Point pStart, Point pEnd, Color color, string name)
{
CG_Line newLine = new CG_Line(pStart, pEnd, color);
newLine.Name = name;
listLine.AddLast(newLine);
curLine = newLine;
drawLine_Bresenham(pStart, pEnd, color);
}
/// <summary>
/// 对当前输入的直线，使用Bresenham算法画出图像
/// </summary>
/// <param name="pStart">直线起点</param>
/// <param name="pEnd">直线终点</param>
/// <param name="color">直线颜色</param>
public void drawLine_Bresenham(Point pStart, Point pEnd, Color color)
{
CG_Line newLine = new CG_Line(pStart, pEnd, color);
foreach (Point cur in newLine.getPoints())
{
drawOnCanvas(cur, color);
}
}
/// <summary>
/// 根据名称改变当前curXXX所指向的图元，返回值表示所选中的图元类型
/// </summary>
/// <param name="name">名称</param>
/// <returns>line直线 circle圆 polygon多边形 rectangle矩形</returns>
public string changeCurPrimitive(string name)
{
LinkedListNode <CG_Line> curL = listLine.First;
while (curL != null)
{
if (curL.Value.Name == name)
{
curLine = curL.Value;
return("line");
}
curL = curL.Next;
}
LinkedListNode <CG_Circle> curC = listCircle.First;
while (curC != null)
{
if (curC.Value.Name == name)
{
curCircle = curC.Value;
return("circle");
}
curC = curC.Next;
}
LinkedListNode <CG_Polygon> curPol = listPolygon.First;
while (curPol != null)
{
if (curPol.Value.Name == name)
{
curPolygon = curPol.Value;
return("polygon");
}
curPol = curPol.Next;
}
LinkedListNode <CG_Rectangle> curRec = listRectangle.First;
while (curRec != null)
{
if (curRec.Value.Name == name)
{
curRectangle = curRec.Value;
return("rectangle");
}
curRec = curRec.Next;
}
LinkedListNode <CG_Bezier> curBez = listBezier.First;
while (curBez != null)
{
if (curBez.Value.Name == name)
{
curBezier = curBez.Value;
return("bezier");
}
curBez = curBez.Next;
}
return(null);
}
/// <summary>
/// 使用Liang-Barsky算法裁剪线段，裁剪窗口为矩形
/// </summary>
/// <param name="line">待裁剪的线段</param>
/// <param name="window">裁剪窗口</param>
/// <returns>裁剪完后的线段</returns>
public CG_Line clipLines_LiangBarsky(CG_Line line, CG_Rectangle window)
{
/*
* 设直线为(x0,y0)->(x1,y1)
* 参数化表示为
* x=x0+u(x1-x0)
* y=y0+u(y1-y0)
* 裁剪条件为
* xmin<=x0+u(x1-x0)<=xmax
* ymin<=y0+u(y1-y0)<=ymax
* 可统一表示为u*pk<=qk (k=0,1,2,3
* 根据pk和qk可以求得裁剪线段的端点
* */
//直线的参数
int x0, y0, x1, y1;
x0 = line.Param.start.X;
y0 = line.Param.start.Y;
x1 = line.Param.end.X;
y1 = line.Param.end.Y;
//裁剪窗口的边界
int xmin, xmax, ymin, ymax;
xmin = window.Left;
xmax = window.Right;
ymin = window.Bottom;
ymax = window.Top;
int[] p = new int[4];
int[] q = new int[4];
p[0] = -1 * (x1 - x0); q[0] = x0 - xmin; //left
p[1] = x1 - x0; q[1] = xmax - x0; //right
p[2] = -1 * (y1 - y0); q[2] = y0 - ymin; //bottom
p[3] = y1 - y0; q[3] = ymax - y0; //top
double u1 = 0, u2 = 1; //初始裁剪端点为原线段的端点
for (int k = 0; k < 4; k++)
{
if (p[k] == 0 && q[k] < 0)
{
return(null); //线段完全在边界外部
}
double r = Convert.ToDouble(q[k]) / Convert.ToDouble(p[k]);
if (p[k] < 0)
{
if (r > u1)
{
u1 = r;
}
}
else//pk>0
{
if (r < u2)
{
u2 = r;
}
}
}
if (u1 > u2)
{
return(null);
}
Point q0 = new Point(x0 + Convert.ToInt32(u1 * (x1 - x0)), y0 + Convert.ToInt32(u1 * (y1 - y0)));
Point q1 = new Point(x0 + Convert.ToInt32(u2 * (x1 - x0)), y0 + Convert.ToInt32(u2 * (y1 - y0)));
CG_Line clippedLine = new CG_Line(q0, q1, line.Param.color);
return(clippedLine);
}
