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;
10. ///
11. //函数声明
12. // Draws an arrow, using the current pen and brush, from the current position
13. //  to the passed point using the attributes defined in the ARROWSTRUCT.
14. void ArrowTo(HDC hDC, int x, int y, ARROWSTRUCT *pArrow);
15. void ArrowTo(HDC hDC, const POINT *lpTo, ARROWSTRUCT *pArrow);
16. ///
17. //画箭头函数实现
18. void CMyDialog::ArrowTo(HDC hDC, int x, int y, ARROWSTRUCT *pA) {
19. POINT ptTo = {x, y};
20. ArrowTo(hDC, &ptTo, pA);
21. }
22. void CMyDialog::ArrowTo(HDC hDC, const POINT *lpTo, ARROWSTRUCT *pA) {
23. POINT pFrom;
24. POINT pBase;
25. POINT aptPoly[3];
26. float vecLine[2];
27. float vecLeft[2];
28. float fLength;
29. float th;
30. float ta;
31. // get from point
32. MoveToEx(hDC, 0, 0, &pFrom);
33. // set to point
34. aptPoly[0].x = lpTo->x;
35. aptPoly[0].y = lpTo->y;
36. // build the line vector
37. vecLine[0] = (float) aptPoly[0].x - pFrom.x;
38. vecLine[1] = (float) aptPoly[0].y - pFrom.y;
39. // build the arrow base vector - normal to the line
40. vecLeft[0] = -vecLine[1];
41. vecLeft[1] = vecLine[0];
42. // setup length parameters
43. fLength = (float) sqrt(vecLine[0] * vecLine[0] + vecLine[1] * vecLine[1]);
44. th = pA->nWidth / (2.0f * fLength);
45. ta = pA->nWidth / (2.0f * (tanf(pA->fTheta) / 2.0f) * fLength);
46. // find the base of the arrow
47. pBase.x = (int) (aptPoly[0].x + -ta * vecLine[0]);
48. pBase.y = (int) (aptPoly[0].y + -ta * vecLine[1]);
49. // build the points on the sides of the arrow
50. aptPoly[1].x = (int) (pBase.x + th * vecLeft[0]);
51. aptPoly[1].y = (int) (pBase.y + th * vecLeft[1]);
52. aptPoly[2].x = (int) (pBase.x + -th * vecLeft[0]);
53. aptPoly[2].y = (int) (pBase.y + -th * vecLeft[1]);
54. MoveToEx(hDC, pFrom.x, pFrom.y, NULL);
55. // draw we're fillin'...
56. if(pA->bFill) {
57. LineTo(hDC, aptPoly[0].x, aptPoly[0].y);
58. Polygon(hDC, aptPoly, 3);
59. }
60. // ... or even jes chillin'...
61. else {
62. LineTo(hDC, pBase.x, pBase.y);
63. LineTo(hDC, aptPoly[1].x, aptPoly[1].y);
64. LineTo(hDC, aptPoly[0].x, aptPoly[0].y);
65. LineTo(hDC, aptPoly[2].x, aptPoly[2].y);
66. LineTo(hDC, pBase.x, pBase.y);
67. MoveToEx(hDC, aptPoly[0].x, aptPoly[0].y, NULL);
68. }
69. }

再来看调用实现(加一层封装更加适用)