MFC中实现的画箭头算法 (Arrow in MFC)

在codeproject中寻找到一个这样的算法,在这里介绍一下

可以改变三角形大小,顶点角度,是否填充和填充颜色等

但是画出的箭头还是不够美观....呵呵,还好吧

其中填充是代表箭头内是否填充颜色 

先来看声明和实现

 

 

1. //使用一个结构体来存储相关的信息
2. //Defines the attributes of an arrow.
3. typedef struct tARROWSTRUCT {
4. int nWidth;     // width (in pixels) of the full base of the arrowhead
5. float fTheta;   // angle (in radians) at the arrow tip between the two
6. //  sides of the arrowhead
7. bool bFill;     // flag indicating whether or not the arrowhead should be
8. //  filled
9. } ARROWSTRUCT;
11. ///
12. //函数声明
13. // Draws an arrow, using the current pen and brush, from the current position
14. //  to the passed point using the attributes defined in the ARROWSTRUCT.
15. void ArrowTo(HDC hDC, int x, int y, ARROWSTRUCT *pArrow);
16. void ArrowTo(HDC hDC, const POINT *lpTo, ARROWSTRUCT *pArrow);
18. ///
19. //画箭头函数实现
20. void CMyDialog::ArrowTo(HDC hDC, int x, int y, ARROWSTRUCT *pA) {
22. POINT ptTo = {x, y};
24. ArrowTo(hDC, &ptTo, pA);
25. }
27. void CMyDialog::ArrowTo(HDC hDC, const POINT *lpTo, ARROWSTRUCT *pA) {
29. POINT pFrom;
30. POINT pBase;
31. POINT aptPoly[3];
32. float vecLine[2];
33. float vecLeft[2];
34. float fLength;
35. float th;
36. float ta;
38. // get from point
39. MoveToEx(hDC, 0, 0, &pFrom);
41. // set to point
42. aptPoly[0].x = lpTo->x;
43. aptPoly[0].y = lpTo->y;
45. // build the line vector
46. vecLine[0] = (float) aptPoly[0].x - pFrom.x;
47. vecLine[1] = (float) aptPoly[0].y - pFrom.y;
49. // build the arrow base vector - normal to the line
50. vecLeft[0] = -vecLine[1];
51. vecLeft[1] = vecLine[0];
53. // setup length parameters
54. fLength = (float) sqrt(vecLine[0] * vecLine[0] + vecLine[1] * vecLine[1]);
55. th = pA->nWidth / (2.0f * fLength);
56. ta = pA->nWidth / (2.0f * (tanf(pA->fTheta) / 2.0f) * fLength);
58. // find the base of the arrow
59. pBase.x = (int) (aptPoly[0].x + -ta * vecLine[0]);
60. pBase.y = (int) (aptPoly[0].y + -ta * vecLine[1]);
62. // build the points on the sides of the arrow
63. aptPoly[1].x = (int) (pBase.x + th * vecLeft[0]);
64. aptPoly[1].y = (int) (pBase.y + th * vecLeft[1]);
65. aptPoly[2].x = (int) (pBase.x + -th * vecLeft[0]);
66. aptPoly[2].y = (int) (pBase.y + -th * vecLeft[1]);
68. MoveToEx(hDC, pFrom.x, pFrom.y, NULL);
70. // draw we're fillin'...
71. if(pA->bFill) {
72. LineTo(hDC, aptPoly[0].x, aptPoly[0].y);
73. Polygon(hDC, aptPoly, 3);
74. }
76. // ... or even jes chillin'...
77. else {
78. LineTo(hDC, pBase.x, pBase.y);
79. LineTo(hDC, aptPoly[1].x, aptPoly[1].y);
80. LineTo(hDC, aptPoly[0].x, aptPoly[0].y);
81. LineTo(hDC, aptPoly[2].x, aptPoly[2].y);
82. LineTo(hDC, pBase.x, pBase.y);
83. MoveToEx(hDC, aptPoly[0].x, aptPoly[0].y, NULL);
84. }
85. }

再来看调用实现(加一层封装更加适用)

 

1. /
2. //封装调用函数实现(其实还是有很大的扩展空间的)
3. void CMyDialog::ArrowTo(
4. CDC *pDC,              //画刷
5. CPoint point,          //终点坐标
6. int nPenStyle,         //线样式
7. int nPenWidth,         //线宽度
8. COLORREF color, //颜色
9. int nWidth,            //三角形底边宽度
10. float fTheta,          //三角形顶角角度
11. bool bFill             //是否填充颜色
12. )
13. {
14. ARROWSTRUCT a;
15. a.nWidth = nWidth;     //三角形底边宽度
16. a.fTheta = fTheta;     //三角形顶角角度
17. a.bFill = bFill;       //是否填充颜色
19. CPen* pOldPen;
20. CPen pen(nPenStyle,nPenWidth,color);
21. pOldPen = pDC->SelectObject(&pen);
23. CBrush br,*pbrOld;
24. br.CreateSolidBrush(color);
25. pbrOld = pDC->SelectObject(&br);
27. ArrowTo(*pDC,point.x,point.y,&a);       //调用画箭头函数
29. pDC->SelectObject(pOldPen);
30. pDC->SelectObject(pbrOld);
31. }