imshow ROI 的大小不同于 ROI.shape

Question

大家晚上好！

我的问题如下：

1.The roi 的形状应该仅为 200,200。这里显示 313,313，我不确定为什么。

2.When 我将 frame 切换为 roi 作为 imshow() 的参数，结果也不是正确的 roi 大小。我得到的是这个输出：

from imutils.video import VideoStream
import argparse
import cv2
import numpy as np
import imutils
import time

ap = argparse.ArgumentParser(description="Pass the .mp4 file and optional buffer size as arguments.")
ap.add_argument("-video", type=str, help="Path to the video file") .
ap.add_argument("-buffer", type=int, default=64, help="Optional max buffer size")
args = vars(ap.parse_args())
video = cv2.VideoCapture(args["video"])
time.sleep(2.0)
offsetx = 38
offsety = 5 

while (video.isOpened()): 
    ret, frame = video.read()
    frame = imutils.resize(frame, width=1280)
    (screenheight, screenwidth) = frame.shape[:2]
    mid_y = screenheight/2
    mid_x = screenwidth /2
    roi_x = (mid_x + offsetx) - 100
    roi_y = (mid_y + offsety) - 100
    roi = frame[int(roi_y):int(roi_x),int(roi_y)+200:int(roi_x)+200]
    cv2.rectangle(frame,(int(roi_x),int(roi_y)),(int(roi_x)+200,int(roi_y)+200),(0,255,0),3)
    print(int(roi_x),int(roi_y),int(roi_x)+200,int(roi_y)+200)
    print(roi.shape)

    cv2.imshow('frame',roi)
        if cv2.waitKey(1) & 0xFF == ord('q'):
        break

video.release()
cv2.destroyAllWindows()

这个文件的输出是：

(313, 313, 3) 578 265 778 465 ...

Answer 1

您的 roi 规格不正确。应该是 [y1:y2, x1:x2] 而不是 [y1:x1, y2:x2]

这里我在一张静态图片上测试：

import cv2

img = cv2.imread('lena.jpg')
height = img.shape[0]
width = img.shape[1]

mid_y = height/2
mid_x = width/2

offset_y = -50
offset_x = -25
y1 = int(mid_y + offset_y) 
x1 = int(mid_x + offset_x)
rows = 100
cols = 50
y2 = y1+rows
x2 = x1+cols
print(y1, y2, x1, x2)

roi = img[y1:y2, x1:x2]
cv2.rectangle(img, (x1,y1), (x2,y2), (0,255,0), 3)
print(roi.shape)

cv2.imshow("ROI", roi)
cv2.waitKey(0)
cv2.destroyAllWindows()

cv2.imwrite("lena_roi.jpg", roi)

打印：

78 178 103 153
(100, 50, 3)

结果：

imshow ROI 的大小不同于 ROI.shape

imshow ROI has different size than ROI.shape

python

opencv

roi