引子

手動版實現帶箭頭的線段繪制

importmath

importcv2ascv
importnumpyasnp

image=cv.imread("D:/images/1024_mask.png")
length=10
angle=45
l1=length*np.cos(angle*np.pi/180)
l2=length*np.sin(angle*np.pi/180)
p1=(100,150)
p2=(400,400)
p3=(0.,0.)
pt4=(0.,0.)

#i,j代表p2、p3、p4相對于p0的正負
ifp2[0]>p1[0]:
i=1
else:
i=-1

ifp2[1]>p1[1]:
j=1
else:
j=-1

#直線p1p2相對于x軸的角度，取正值
a1=abs(math.atan((p2[1]-p1[1])/(p2[0]-p1[0])))

#用于計算p2相對于p0的寬高
w1=l1*math.cos(a1)
h1=l1*math.sin(a1)
p0=(p2[0]-w1*i,p2[1]-h1*j);

#直線p3p4相對于x軸的角度
a2=90*np.pi/180-a1;
w2=l2*np.cos(a2)

#用于計算p3和p4相對于p0的寬高
h2=l2*np.sin(a2)
p3=(int(p0[0]-w2*i),int(p0[1]+h2*j))
p4=(int(p0[0]+w2*i),int(p0[1]-h2*j))
cv.line(image,p1,p2,(0,255,0),2,8,0)

#畫箭頭
cv.line(image,p2,p3,(0,255,0),2,8,0)
cv.line(image,p2,p4,(0,255,0),2,8,0)
cv.imshow("arrow-linedemo",image)
cv.waitKey(0)
cv.destroyAllWindows()

其實沒那么復雜

voidcv::arrowedLine(
InputOutputArrayimg,#輸入圖像
Pointpt1,#線段端點
Pointpt2,
constScalar&color,#顏色
intthickness=1,#線寬
intline_type=8,#渲染類型
intshift=0,
doubletipLength=0.1
)

importcv2ascv

image=cv.imread("D:/images/1024_mask.png")
cv.arrowedLine(image,(100,150),(400,400),(0,255,0),2,8,0,0.05)
cv.imshow("arrow-linedemo",image)
cv.waitKey(0)
cv.destroyAllWindows()