最近遇到需要求图形轮廓中距离最远的点，即长轴。
网上查了一些资料，思路如下。
1. 利用OpenCV提取图形的轮廓点。
2. 把提取到的所有轮廓点当做一个集合，再次提取最外面的轮廓。
3. 用凸包旋转卡克方法求解。
1 private async void Calculate()
2 {
3
4
5 var a = new Image<Bgr, byte>((Bitmap)pictureBox1.Image);
6 var b = new Image<Gray, byte>(a.Width, a.Height);
7 var c = new Image<Gray, byte>(a.Width, a.Height);
8 var d = new Image<Bgr, byte>(a.Width, a.Height);
9
10 var t1 = trackBar1.Value;
11 var t2 = trackBar2.Value;
12
13 CvInvoke.Canny(a, b, t1, t2);
14 var con = new VectorOfVectorOfPoint();
15 CvInvoke.FindContours(b, con, c, RetrType.Ccomp, ChainApproxMethod.ChainApproxSimple);
16
17
18 var con1 = con.ToArrayOfArray();
19 var con2 = Array.ConvertAll<Point[], PointF[]>(con1, new Converter<Point[], PointF[]>(PointToPointF));
20
21 var points = new List<PointF>(con2.Length);
22 foreach (PointF[] t in con2)
23 {
24 for (int j = 0; j < t.Length; j++)
25 {
26 points.Add(t[j]);
27 }
28 }
29
30 //找出凸包
31 var hull = CvInvoke.ConvexHull(points.ToArray(), true);
32
33 var color = new MCvScalar(34, 177, 76);
34 //画出轮廓
35 for (int j = 0; j < hull.Length; j++)
36 {
37 var p1 = new Point((int)(hull[j].X + 0.5), (int)(hull[j].Y + 0.5));
38 Point p2;
39 if (j == hull.Length - 1)
40 p2 = new Point((int)(hull[0].X + 0.5), (int)(hull[0].Y + 0.5));
41 else
42 p2 = new Point((int)(hull[j + 1].X + 0.5), (int)(hull[j + 1].Y + 0.5));
43 //CvInvoke.Circle(d, p1, 3, color);
44 CvInvoke.Line(a, p1, p2, color);
45 }
46
47 int pp1 = 0, pp2 = 0, pp3 = 0;
48 Find(hull, ref pp1, ref pp2, ref pp3, ref a);
49
50 Console.WriteLine("Find1 p1={0}, p2={1}", pp1, pp3);
51
52 double k = 0, bb = 0d;
53 CalculateLineFormula(hull[pp1], hull[pp2], ref k, ref bb);
54
55 var tmp1 = new Point((int)(hull[pp1].X + 0.5), (int)(hull[pp1].Y + 0.5));
56
57 //var tmp2 = new Point((int)(hull[pp2].X + 0.5), (int)(hull[pp2].Y + 0.5));
58 var tmp3 = new Point((int)(hull[pp3].X + 0.5), (int)(hull[pp3].Y + 0.5));
59 CvInvoke.Line(a, tmp1, tmp3, color);
60 imageBox1.Image = a;
61
62 }
63
64
65
66 /// <param name="p2Index"></param>
67 public void Find2(PointF[] points, ref int p1Index, ref int p3Index)
68 {
69 var max = double.MinValue;
70
71 for (int i = 0; i < points.Length; i++)
72 {
73 for (int j = 0; i < points.Length; i++)
74 {
75 var dis = CalculateDisOfPoints(points[i], points[j]);
76 if (!(dis > max)) continue;
77 max = dis;
78 p1Index = i;
79 p3Index = j;
80
81 Console.WriteLine("Find2 max={0}", max);
82 }
83 }
84 }
85
86
87 private Point ConvetT(PointF p)
88 {
89 return new Point((int)p.X, (int)p.Y);
90 }
91
92
93
94 /// <summary>
95 /// 计算两个距离最长的对点
96 /// </summary>
97 /// <param name="points"></param>
98 /// <param name="p1Index"></param>
99 /// <param name="p2Index"></param>
100 public void Find(PointF[] points, ref int p1Index, ref int p2Index, ref int p3Index, ref Image<Bgr, byte> image)
101 {
102
103 var maxYPos = -1;
104 var minYPos = -1;
105 var maxDis = 0d;
106
107 var len = points.Length;
108 //先寻找最大的Y
109 FindMax(points, ref maxYPos, ref minYPos);
110 p1Index = maxYPos;
111 p2Index = (maxYPos + 1) % len;
112 p3Index = minYPos;
113 //对重点
114 maxDis = CalculateDisOfPoints(points[maxYPos], points[minYPos]);
115 Console.WriteLine("max={0}", maxDis);
116 var cnt = 0;
117
118 var n1 = (maxYPos )%len;
119 var n2 =(minYPos) % len ;
120
121 //四个向量
122 PointF vec1, vec2, vec3, vec4;
123 vec1 = new PointF(1, 0); //指向右边
124 vec3= new PointF(-1,0); //指向左边
125 var offset1 = 0;
126 var offset2 = 0;
127 //顺时针旋转一周
128 var color = new MCvScalar(34, 177, 76);
129 while(offset1<len && offset2<len)
130 {
131 var tmpImg = image.Copy();
132 var p1 = points[ (n1+offset1)%len];
133 var p2 = points[ (n1+offset1+1)%len];
134 vec2 = new PointF(p2.X - p1.X, p2.Y - p1.Y);
135
136
137 var p3 = points[ (n2+offset2)%len];
138 var p4 = points[ (n2 + offset2+1) % len];
139 vec4= new PointF(p4.X - p3.X, p4.Y - p3.Y);;
140
141 //计算向量夹角
142 var ang12 = CalculateAngle(vec1, vec2);
143 var ang34 = CalculateAngle(vec3, vec4);
144
145 var dis = 0d;
146 if(ang12<ang34)
147 {
148 //12夹角比较小, 计算p2与p3的距离
149 dis = CalculateDisOfPoints(p2, p3);
150 if (dis -maxDis>0.000001)
151 {
152 maxDis = dis;
153 p1Index = (n1 + offset1 + 1) % len;
154 p3Index = (n2 + offset2) % len;
155
156 //CvInvoke.Line(image, ConvetT(points[p1Index]), ConvetT(points[p3Index]), color);
157 //imageBox1.Image = image;
158 }
159
160 //经过p3点的与vec1反方向的平行线
161 vec3 = new PointF(-vec1.X, -vec1.Y);
162 //更新向量
163 vec1 = vec2;
164
165 //转动
166 offset1++;
167
168 Console.WriteLine("Find1 max={0}", maxDis);
169 }
170 else
171 {
172 //12夹角比较小, 计算p2与p3的距离
173 dis = CalculateDisOfPoints(p1, p4);
174 if (dis - maxDis > 0.000001)
175 {
176 maxDis = dis;
177 p1Index = (n1 + offset1) % len;
178 p3Index = (n2 + offset2 + 1) % len;
179 }
180
181 //转动
182 offset2++;
183 //经过p3点的与vec1反方向的平行线
184 vec1 = new PointF(-vec3.X, -vec3.Y);
185 vec3 = vec4;
186 Console.WriteLine("Find1 max={0}", maxDis);
187 }
188 }
189 }
190
191
192 /// <summary>
193 /// 计算经过两个点p1,p2的直线
194 /// </summary>
195 /// <param name="p1">点1</param>
196 /// <param name="p2">点2</param>
197 /// <param name="k">斜率</param>
198 /// <param name="b"></param>
199 private void CalculateLineFormula(PointF p1, PointF p2, ref double k,ref double b)
200 {
201 var dX = p1.X - p2.X;
202 var dY = p2.Y - p2.Y;
203
204 if(dX==0)
205 {
206 //X=C
207 k = 1;
208 b = 0;
209
210 }
211 else if(dY==0)
212 {
213 k = 0;
214 b = 0;
215 }
216 else
217 {
218 k = (double)dY / dX;
219 b = p1.Y - p1.X * k;
220 }
221 }
222
223 /// <summary>
224 /// 计算平行线的距离
225 /// </summary>
226 /// <param name="k"></param>
227 /// <param name="b1"></param>
228 /// <param name="b2"></param>
229 /// <returns></returns>
230 private double CalculateLinesDis(double k, double b1, PointF p1, PointF p2)
231 {
232 var toll=0.000001d;
233 if (Math.Abs(k) < toll) // x=常熟
234 return Math.Abs(p1.X-p2.X);
235 else if (Math.Abs(k)-1 < toll) //y=常数
236 return Math.Abs(p1.Y-p2.Y);
237 else
238 {
239 //line 1, ax+by=c
240 var a = -k;
241 var b = 1;
242 var c = b1;
243 //计算p2到 line1的距离
244 return Math.Abs(a * p1.X + b * p1.Y + c) / Math.Sqrt(a * a + b * b);
245 }
246
247 }
248
249
250
251 /// <summary>
252 /// 先寻找一对对踵点
253 /// </summary>
254 /// <param name="points"></param>
255 /// <param name="maxPos"></param>
256 /// <param name="minPos"></param>
257 private void FindMax(PointF[] points, ref int maxPos, ref int minPos)
258 {
259 var max = double.MinValue;
260 var min = double.MaxValue;
261
262 for (int i = 0; i < points.Length; i++)
263 {
264 if(points[i].Y>max)
265 {
266 max = points[i].Y;
267 maxPos = i;
268 }
269 if (points[i].Y < min)
270 {
271 min = points[i].Y;
272 minPos = i;
273 }
274 }
275
276 }
277
278
279
280 private double CalculateDisOfPoints(PointF p1, PointF p2)
281 {
282 return Math.Sqrt( (p1.Y-p2.Y)*(p1.Y-p2.Y)+(p1.X-p2.X)*(p1.X-p2.X));
283 }
284
285
286 /// <summary>
287 /// 计算两个向量的夹角，0-180度
288 /// </summary>
289 /// <param name="vec1">向量1</param>
290 /// <param name="vec2">向量2</param>
291 /// <returns></returns>
292 private double CalculateAngle(PointF vec1, PointF vec2)
293 {
294 //var ang=Math.Atan(k2-k1)
295
296 var toll=0.0000001;
297
298 if (vec1.X * vec2.X + vec1.Y * vec2.Y < toll)
299 return 90;
300
301
302 if(Math.Abs(vec1.X)<toll )
303 {
304
305 }
306
307
308 var sum1 = Math.Sqrt(vec1.X*vec1.X+vec1.Y*vec1.Y);
309 var sum2 = Math.Sqrt(vec2.X * vec2.X + vec2.Y * vec2.Y);
310
311 if (sum1 + sum2 < toll)
312 return 0;
313
314 var sum3 = vec1.X * vec2.X + vec1.Y * vec2.Y;
315 var ang = Math.Acos(sum3 / (sum1 * sum2))*180/Math.PI;
316 return ang;
317 }
效果如下：
参考资料：
http://www.cnblogs.com/Booble/archive/2011/04/03/2004865.html
时间： 2024-10-22 10:01:19