MFC中实现的画箭头算法(ArrowinMFC)
发布时间：2010/5/18 11:47:10 来源：城市学习网 编辑：ziteng
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
//使用一个结构体来存储相关的信息
//Defines the attributes of an arrow.
typedef struct tARROWSTRUCT {
int nWidth; // width (in pixels) of the full base of the arrowhead
float fTheta; // angle (in radians) at the arrow tip between the two
// sides of the arrowhead
bool bFill; // flag indicating whether or not the arrowhead should be
// filled
} ARROWSTRUCT;
///////////////////////
//函数声明
// Draws an arrow, using the current pen and brush, from the current position
// to the passed point using the attributes defined in the ARROWSTRUCT.
void ArrowTo(HDC hDC, int x, int y, ARROWSTRUCT *pArrow);
void ArrowTo(HDC hDC, const POINT *lpTo, ARROWSTRUCT *pArrow);
///////////////////////
//画箭头函数实现
void CMyDialog::ArrowTo(HDC hDC, int x, int y, ARROWSTRUCT *pA) {
POINT ptTo = {x, y};
ArrowTo(hDC, &ptTo, pA);
}
void CMyDialog::ArrowTo(HDC hDC, const POINT *lpTo, ARROWSTRUCT *pA) {
POINT pFrom;
POINT pBase;
POINT aptPoly[3];
float vecLine[2];
float vecLeft[2];
float fLength;
float th;
float ta; [NextPage] [NextPage] // get from point
MoveToEx(hDC, 0, 0, &pFrom);
// set to point
aptPoly[0].x = lpTo->x;
aptPoly[0].y = lpTo->y;
// build the line vector
vecLine[0] = (float) aptPoly[0].x - pFrom.x;
vecLine[1] = (float) aptPoly[0].y - pFrom.y;
// build the arrow base vector - normal to the line
vecLeft[0] = -vecLine[1];
vecLeft[1] = vecLine[0];
// setup length parameters
fLength = (float) sqrt(vecLine[0] * vecLine[0] + vecLine[1] * vecLine[1]);
th = pA->nWidth / (2.0f * fLength);
ta = pA->nWidth / (2.0f * (tanf(pA->fTheta) / 2.0f) * fLength);
// find the base of the arrow
pBase.x = (int) (aptPoly[0].x + -ta * vecLine[0]);
pBase.y = (int) (aptPoly[0].y + -ta * vecLine[1]);
// build the points on the sides of the arrow
aptPoly[1].x = (int) (pBase.x + th * vecLeft[0]);
aptPoly[1].y = (int) (pBase.y + th * vecLeft[1]);
aptPoly[2].x = (int) (pBase.x + -th * vecLeft[0]);
aptPoly[2].y = (int) (pBase.y + -th * vecLeft[1]);
MoveToEx(hDC, pFrom.x, pFrom.y, NULL);
// draw we're fillin'...
if(pA->bFill) {
LineTo(hDC, aptPoly[0].x, aptPoly[0].y);
Polygon(hDC, aptPoly, 3);
