我正在尝试在我使用opencv2在python中从笔记本电脑的相机录制的帧上绘制矩形。
但是,从cv2.rectangle函数返回的图像是None
。为什么呢?
import numpy as np
import cv2
# details of rectangle to be drawn.
x, y, h, w = (493, 305, 125, 90)
cap = cv2.VideoCapture(0)
while 1:
ret, frame = cap.read()
if not ret or not frame:
# camera didn't give us a frame.
continue
# attempt to draw a rectangle.
img = cv2.rectangle(frame, (x, y), (x + w, y + h), (0, 255, 0), 2)
# This prints out None every time! why?
print str(img)
if not img:
continue
# We never get here since img is None. :/
cv2.imshow('img', img)
如果相机中的帧为空,我已经尝试添加检查。我也尝试确保矩形实际上适合框架。
我确信我的相机正在工作,因为我可以成功imshow
画面。
答案 0 :(得分:10)
rectangle不会返回任何内容
[edit:]在opencv2.4.x中,但它 返回opencv3.0 / python中的图像
还要注意,非常受欢迎的py_tutrorials是3.0,所以不要混淆;)
import numpy as np
import cv2
# details of rectangle to be drawn.
x, y, h, w = (493, 305, 125, 90)
cap = cv2.VideoCapture(0)
while 1:
ret, frame = cap.read()
if not ret or not frame:
# camera didn't give us a frame.
continue
# draw a rectangle.
cv2.rectangle(frame, (x, y), (x + w, y + h), (0, 255, 0), 2)
# show it ;)
cv2.imshow('img', frame)