在codeproject中尋找到一個這樣的算法,在這里介紹一下

可以改變三角形大小,頂點角度,是否填充和填充顏色等

但是畫出的箭頭還是不夠美觀....呵呵,還好吧

其中填充是代表箭頭內是否填充顏色?

先來看聲明和實現

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//使用一個結構體來存儲相關的信息

//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;

///

//函數聲明

// 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);

///

//畫箭頭函數實現

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;

// 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);

}

// ... or even jes chillin'...

else {

LineTo(hDC, pBase.x, pBase.y);

LineTo(hDC, aptPoly[1].x, aptPoly[1].y);

LineTo(hDC, aptPoly[0].x, aptPoly[0].y);

LineTo(hDC, aptPoly[2].x, aptPoly[2].y);

LineTo(hDC, pBase.x, pBase.y);

MoveToEx(hDC, aptPoly[0].x, aptPoly[0].y, NULL);

}

}

再來看調用實現(加一層封裝更加適用)

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//封裝調用函數實現(其實還是有很大的擴展空間的)

void CMyDialog::ArrowTo(

CDC *pDC,? ? ? ?? ? ? ?//畫刷

CPoint point, ? ? ? ? ?//終點坐標

int nPenStyle, ?? ? ? ?//線樣式

int nPenWidth, ?? ? ? ?//線寬度

COLORREF color,?//顏色

int nWidth,? ? ?? ? ? ?//三角形底邊寬度

float fTheta,? ?? ? ? ?//三角形頂角角度

bool bFill? ? ? ? ? ? ?//是否填充顏色

)

{

ARROWSTRUCT a;

a.nWidth = nWidth;? ? ?//三角形底邊寬度

a.fTheta = fTheta;? ? ?//三角形頂角角度

a.bFill = bFill;? ? ? ?//是否填充顏色

CPen* pOldPen;

CPen pen(nPenStyle,nPenWidth,color);

pOldPen = pDC->SelectObject(&pen);

CBrush br,*pbrOld;

br.CreateSolidBrush(color);

pbrOld = pDC->SelectObject(&br);

ArrowTo(*pDC,point.x,point.y,&a);? ? ? ?//調用畫箭頭函數

pDC->SelectObject(pOldPen);

pDC->SelectObject(pbrOld);

}

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轉載于:https://www.cnblogs.com/wupingzsf/archive/2010/05/16/1736958.html

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