因为线图像startline有了起点和终点，我们就可以用DDA法求出线上所有点，任意斜率直线通过四象限八区域查表法界定。我们只示范一个区域：函数为： public PointF DdaFindPtImprove(ref byte[] buffer8, PointF Start, PointF End, int thresDelta, int Dir,Size wh,ref int Pos)//thresDelta门槛值，Pos线图像中穿越点index
{ float x, y;
float dx, dy, k;
PointF backPoint = new PointF();
dx = (float)(End.X - Start.X);
dy = (float)(End.Y - Start.Y);
k = dy / dx;
if (Math.Abs(dx) < 0.001)
{
k = 65535;//随意给定一个最大值，还需论证。20150727，够用
}
x = Start.X;
if (Start.Y < 0) Start.Y = 0;
y = Start.Y;
List<float> temparrclor = new List<float>(); // 线图像上每一个点灰度颜色
List<PointF> position = new List<PointF>();//线图像上每一个点坐标
#region xiaoyu1
if (Math.Abs(k) < 1)
{
if (x > End.X)
{
for (; x >= End.X; x--)//x是整型，y是浮点型
{
float j = y;
int i = (int)(x);
float tempf = Math.Abs(j - (int)j);
PointF tempPt = new PointF(i, j);
float grey = 0;
if (k > -1 && k <= 0)
{
float avgGrey = (float)buffer8[(int)j * wh.Width + i];
float avgGrey1 = (float)buffer8[((int)j + 1) * wh.Width + i];
grey = avgGrey * (1 - tempf) + avgGrey1 * tempf;//灰度插值方法
}
else
{
float avgGrey = (float)buffer8[(int)j * wh.Width + i];
float avgGrey1 = (float)buffer8[((int)j - 1) * wh.Width + i];
grey = avgGrey * (1 - tempf) + avgGrey1 * tempf;
}
temparrclor.Add(grey);//插值灰度
position.Add(tempPt);
y = y - k;
}
backPoint = FindCrosspointimprove(ref temparrclor, ref position, Dir, thresDelta,ref Pos);//找穿越点
}
else {.......}
}
#endregion xiaoyu1
........ return backPoint;}
public PointF FindCrosspointimprove(ref List<float> lineTiDu, ref List<PointF> ijRecord, int Dir, int thresDelta,ref int POS)
{//梯度和求穿越点，使用五个一组，与所讲略有差别
List<float> deltatemp = new List<float>();
List<float> fenzuaverage = new List<float>();
for (int i = 0; i < lineTiDu.Count - 1; i++)
{
float grey1 = lineTiDu[i + 1];
float delta = (lineTiDu[i] - grey1);
if (Math.Abs(delta) < 5)
delta = 0;
deltatemp.Add(delta);
}
int fenzuC = deltatemp.Count / 5;
for (int i = 0; i < fenzuC * 5; i = i + 5)
{
float sum5 = deltatemp[i] + deltatemp[i + 1] + deltatemp[i + 2] + deltatemp[i + 3] + deltatemp[i + 4];
float aver = sum5 / 5;
if (Math.Abs(aver) < 5)
aver = 0;
fenzuaverage.Add(aver);
}
if (fenzuaverage.Count == 0) return new PointF();
int crosspoint = 0;
int crosspoint1 = 0;
if (Dir == 0)
{
for (int iii = fenzuaverage.Count - 1; iii >= 0; iii--)//排除起点和终点
{
if (fenzuaverage[iii] > 0)
{
crosspoint = 5 * (iii);
break;
}
}
float maxVar = deltatemp[crosspoint];
for (int m = -5; m < 5; m++)
{
int tempint = crosspoint + m;
if (crosspoint == 0)
tempint = 0;
if (deltatemp[tempint] >= maxVar)//白到黑，加入方向判别
{
maxVar = deltatemp[tempint];
crosspoint1 = tempint;
}
}
}
if (Dir == 1)
{
for (int iii =0 ; iii <= fenzuaverage.Count - 1; iii++)//排除起点和终点
{
if (fenzuaverage[iii] < 0)
{
crosspoint = 5 * (iii);
break;
}
}
// minVar = deltatemp[crosspoint];
float minVar = deltatemp[crosspoint];
for (int m = -5; m < 5; m++)
{
int tempint = crosspoint + m;
if (crosspoint == 0)
tempint = 0;
if (deltatemp[tempint] <= minVar)//白到黑，加入方向判别
{
minVar = deltatemp[tempint];
crosspoint1 = tempint;
}
}
}
if (fenzuaverage[crosspoint / 5] * 5 >= thresDelta || fenzuaverage[crosspoint / 5] * 5 <= -thresDelta)
{
POS = crosspoint1;//穿越点的index在线图像序列中
return ijRecord[crosspoint1];//穿越点的index对应坐标
}//门槛判别
else
{
return new PointF();//没有穿越点，返回（0,0）
}
}
一切准备就绪，在private void pictureBoxRoiImg_Paint(object sender, PaintEventArgs e)调用
if (m_btempImage3 == true)//截取的ROI图像
{
PointF startxy = m_线图像.m_RoiBase.startLine.pt_start;
PointF endxy = m_线图像.m_RoiBase.startLine.pt_end;
PointF returnpoint = DdaFindPtImprove(ref tempImage3, startxy,
endxy, 门槛值, glob_Dir, new Size(_RoiW, _RoiH), ref pos);
p = new Pen(Color.Red, 1);//画出穿越点叉叉
g.DrawLine(p, new PointF(returnpoint.X, returnpoint.Y - 3), new PointF(returnpoint.X, returnpoint.Y + 3));
g.DrawLine(p, new PointF(returnpoint.X - 3, returnpoint.Y), new PointF(returnpoint.X + 3, returnpoint.Y));
}
到此，线图像设计完成。下一节讲一组线图像组成找线工具。（待续..............）以下是运行后线图像工具效果：
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