------cv2 draw vessels-------
vessel1 = A[0]
vessel2 = A[1]
color_list = [(255,0,0),(0,255,0),(0,0,255),(128,128,0),(128,0,128),(0,128,128)]
img1 = np.zeros((512,512,3),np.uint8)
img2 = np.zeros((512,512,3),np.uint8)
for idx in range((len(vessel1))):
    seg = vessel1[idx]
    clr = color_list[idx]
    for pt in seg:
        pt = (pt[1],pt[0])
        cv2.circle(img1,pt,1,clr,-1)

for idx in range((len(vessel2))):
    seg = vessel2[idx]
    clr = color_list[idx]
    for pt in seg:
        pt = (pt[1],pt[0])
        cv2.circle(img2,pt,1,clr,-1)

cv2.imwrite('1.png',img1)
cv2.imwrite('2.png',img2)

cv2.imshow('img1', img1)
cv2.imshow('img2',img2)
cv2.waitKey(0)
cv2.destroyAllWindows()