判断点在凸多边形内

// cocos2dx

int cross = 0;

CCPoint pos = getPosition();
CCPoint point_origin = CCPointMake(pos.x + m_rectTouch.origin.x, pos.y + m_rectTouch.origin.y);

int valid_pointnum = m_curShapePoint->GetValidPointNum();

for (int i = 0; i < valid_pointnum; ++i)
{
　　CCPoint p1 = ccpAdd(ccp(m_curShapePoint->m_fShapePosX[i], m_curShapePoint->m_fShapePosY[i]), point_origin);
　　CCPoint p2 = ccpAdd(ccp(m_curShapePoint->m_fShapePosX[(i + 1) % valid_pointnum], m_curShapePoint->m_fShapePosY[(i + 1) % valid_pointnum]), point_origin);

　　if (p1.y == p2.y)
　　　　continue;

　　if (point.y < MIN(p1.y, p2.y))
　　　　continue;

　　if (point.y >= MAX(p1.y, p2.y))
　　　　continue;

　　float x = (float)(point.y - p1.y) * (p2.x - p1.x) / (p2.y - p1.y) + p1.x;

　　if (x > point.x)
　　　　cross++;
}

return (cross % 2 == 1);