/// <summary>
/// 二维Line2Block实现
/// </summary>
/// <param name="gridWidth">格的宽度</param>
/// <param name="gridHeight">格的高度</param>
/// <param name="startPosition">线段开始点</param>
/// <param name="endPosition">线段终止点</param>
/// <returns>线段所经过的方块的中点坐标集合（不包括开始点和终止点所在的方块），如果是空集直接返回NULL</returns>
public IPositionSet WriteLineInGrid(float gridWidth, float gridHeight, IPosition startPosition, IPosition endPosition)
{
//归一化处理
float temp;
float endx = endPosition.GetX() / gridWidth;
float startx = startPosition.GetX() / gridWidth;
float endy = endPosition.GetY() / gridHeight;
float starty = startPosition.GetY() / gridHeight;
float dx = endx - startx;
float dy = endy - starty;
//如果两点在同一个方块里就返回空
if ((int)startx == (int)endx && (int)starty == (int)endy)
{
//positionSet.AddPosition(new Position_Point(((int)startx+0.5f)*gridWidth,((int)starty+0.5f)*gridHeight));
return(null);
}
PositionSetEdit_ImplementByICollectionTemplate positionSet = new PositionSetEdit_ImplementByICollectionTemplate();
if (Math.Abs(dx) > Math.Abs(dy))
{
//保证起点x坐标小于终点x坐标
if (startx > endx)
{
temp = startx; startx = endx; endx = temp;
temp = starty; starty = endy; endy = temp;
dx = -dx;
dy = -dy;
}
//添加起点所在的方块
//positionSet.AddPosition(new Position_Point(((int)startx + 0.5f) * gridWidth, ((int)starty + 0.5f) * gridHeight));
float slope = dy / dx;
float x = (int)startx + 1;
float y = (x - startx) * slope + starty;//算出第一个边界值
float oldy = y;
//添加可能出现的与起点所在分块同一列的方块
if ((int)y != (int)starty)
{
positionSet.AddPosition(new Position_Point(((int)x - 1 + 0.5f) * gridWidth, ((int)y + 0.5f) * gridHeight));
}
//迭代所有边界值
for (int i = 0; i < (int)endx - (int)startx - 1; i++)
{
oldy = y;
x += 1;
y += slope;
positionSet.AddPosition(new Position_Point(((int)x - 1 + 0.5f) * gridWidth, ((int)oldy + 0.5f) * gridHeight));
if ((int)oldy != (int)y)
{
positionSet.AddPosition(new Position_Point(((int)x - 1 + 0.5f) * gridWidth, ((int)y + 0.5f) * gridHeight));
}
}
//添加可能出现的与终点所在分块同一列的方块
if ((int)y != (int)endy)
{
positionSet.AddPosition(new Position_Point(((int)x + 0.5f) * gridWidth, ((int)y + 0.5f) * gridHeight));
}
}
else
{
//保证起点y坐标小于终点y坐标
if (starty > endy)
{
temp = startx; startx = endx; endx = temp;
temp = starty; starty = endy; endy = temp;
dx = -dx;
dy = -dy;
}
//添加起点所在的方块
//positionSet.AddPosition(new Position_Point(((int)startx + 0.5f) * gridWidth, ((int)starty + 0.5f) * gridHeight));
float slope = dx / dy;
float y = (int)starty + 1;
float x = (y - starty) * slope + startx;//算出第一个边界值
float oldx = x;
//添加可能出现的与终点所在分块同一行的方块
if ((int)x != (int)startx)
{
positionSet.AddPosition(new Position_Point(((int)x + 0.5f) * gridWidth, ((int)y - 1 + 0.5f) * gridHeight));
}
//迭代所有边界值
for (int i = 0; i < (int)endy - (int)starty - 1; i++)
{
oldx = x;
x += slope;
y += 1;
positionSet.AddPosition(new Position_Point(((int)oldx + 0.5f) * gridWidth, ((int)y - 1 + 0.5f) * gridHeight));
if ((int)oldx != (int)x)
{
positionSet.AddPosition(new Position_Point(((int)x + 0.5f) * gridWidth, ((int)y - 1 + 0.5f) * gridHeight));
}
}
//添加可能出现的与终点所在分块同一行的方块
if ((int)x != (int)endx)
{
positionSet.AddPosition(new Position_Point(((int)x + 0.5f) * gridWidth, ((int)y + 0.5f) * gridHeight));
}
}
return(positionSet.GetNum() == 0?null:positionSet);
}