public int intersectWithY(int y, out int x)
{
int dyStart = m_start.Y - y;
int dyEnd = m_end.Y - y;
if (dyStart == 0 && dyEnd == 0)
{
x = 0;
return(2); // 无穷个交点
}
else if (dyStart * dyEnd <= 0)
{
if (m_start.Y <= m_end.Y)
{
float f = HelpFuncs.SmoothStep(m_start.Y, m_end.Y, y);
x = (int)HelpFuncs.Lerp(m_start.X, m_end.X, f);
}
else
{
float f = HelpFuncs.SmoothStep(m_end.Y, m_start.Y, y);
x = (int)HelpFuncs.Lerp(m_end.X, m_start.X, f);
}
return(1); // 1个焦点
}
else
{
x = 0;
Debug.Assert(dyStart * dyEnd > 0);
return(0);
}
}
public void Draw(Bitmap bm, BitmapData bmData, Color c)
{
LineSegment[] lineSegs =
{
new LineSegment((Point)m_pts[0], (Point)m_pts[1]),
new LineSegment((Point)m_pts[1], (Point)m_pts[2]),
new LineSegment((Point)m_pts[2], (Point)m_pts[0]),
};
int minY = Math.Max(Math.Min(Math.Min((int)m_pts[0].Y, (int)m_pts[1].Y), (int)m_pts[2].Y), 0);
int maxY = Math.Min(Math.Max(Math.Max((int)m_pts[0].Y, (int)m_pts[1].Y), (int)m_pts[2].Y), bm.Height - 1);
for (int y = minY; y <= maxY; ++y)
{
int xCnt = 0;
int x1 = 0, x2 = 0;
for (int i = 0; i < lineSegs.Length; ++i)
{
int tx = 0, tIntersectCnt = 0;
tIntersectCnt = lineSegs[i].intersectWithY(y, out tx);
if (tIntersectCnt == 0)
{
continue;
}
else if (tIntersectCnt == 2)
{
x1 = lineSegs[i].Start.X; x2 = lineSegs[i].End.X; xCnt = 2; break;
}
else
{
if (xCnt == 0)
{
x1 = tx; xCnt = 1;
}
else if (xCnt == 1)
{
x2 = tx; xCnt = 2;
}
else
{
if (x1 == x2)
{
x2 = tx;
}
break;
}
}
}
if (xCnt == 0)
{
continue;
}
Debug.Assert(xCnt == 2);
if (x1 > x2)
{
HelpFuncs.Swap(ref x1, ref x2);
}
x1 = Math.Max(x1, 0);
x2 = Math.Min(x2, bm.Width - 1);
unsafe
{
int *p = (int *)bmData.Scan0 + y * bmData.Stride / 4;
int argb = c.ToArgb();
for (int x = x1; x <= x2; ++x)
{
p[x] = argb;
}
}
}
}
