python - 在 PyGame 中绘制沿直线方向的箭头

Question

在 Pygame 中，给定箭头的起点和终点，如何计算箭头头部三个点的坐标，使箭头指向与直线相同的方向？

def __draw_arrow(self, screen, colour, start, end):     
    start = self.__coordinate_lookup[start]
    end = self.__coordinate_lookup[end]
    dX = start[0] - end[0]
    dY = -(start[1] - end[1])
    print m.degrees(m.atan(dX/dY)) + 360 
    pygame.draw.line(screen,colour,start,end,2)

我尝试过调整角度和线的渐变，Y 坐标向下而不是向上增加这一事实让我失望，我真的很感激向正确的方向轻推。

Answer 1

我将开始和结束坐标表示为 startX, startY, endX, endY

dX = endX - startX
dY = endY - startY

//vector length 
Len = Sqrt(dX* dX + dY * dY)  //use Hypot if available

//normalized direction vector components
udX = dX / Len
udY = dY / Len

//perpendicular vector
perpX = -udY
perpY = udX

//points forming arrowhead
//with length L and half-width H
arrowend  = (end) 

leftX = endX - L * udX + H * perpX
leftY = endY - L * udY + H * perpY

rightX = endX - L * udX - H * perpX
rightY = endY - L * udY - H * perpY