python - Opencv-Python输入数组错误

Question

我最近开始探索 OpenCV，对此我非常了解。我在显示原始视频帧内的缩放视频帧时遇到问题。希望这是有道理的。一切正常，但是当我尝试更改缩放视频的颜色时，出现错误。这是我的代码，希望它能 self 解释。

import cv2
import numpy as np

cap = cv2.VideoCapture(0)

while True:
    #"ret" returns a frame
    ret, frame = cap.read()

    #Draw a rectangle at given location
    cv2.rectangle(frame,(500,80),(800,380),(0,255,0),5)

    #takes a sample of the frame marked by the rectangle area(y,x)
    face_track = frame[80:380, 500:800]
    #converts the sample to gray
    grayscaled = cv2.cvtColor(face_track,cv2.COLOR_BGR2GRAY)
    #threshold range of sample
    retvl, threshold = cv2.threshold(grayscaled,125,125,cv2.THRESH_BINARY)

    #overwrites/display a new area with the sample taken by face_track in the left top corner of the frame
    frame[0:300, 0:300] = threshold

    #displays the frames captured by cap
    cv2.imshow('frame',frame)
    #cv2.imshow('frame',threshold)

    #if key stroke is 'q' break and terminate 
    if cv2.waitKey(0) & 0xff == ord('q'): 
        break

cap.release()
cv2.destroyAllWindows()

错误如下:

frame[0:300, 0:300] = threshold ValueError: could not broadcast input array from shape (300,300) into shape (300,300,3)

如果我把它改成这样:

frame[0:300, 0:300] = face_track

它有效。但这不是我想要的。

此外，如果我改为输出阈值，cv2.imshow('frame',threshold),它也会起作用。但同样不是我想要的。

除了cv2.cvtColor之外，还有其他函数不会改变数组的形状吗？

Answer 1

将 thresh gray 转换为 BGR

cv2.cvtColor(阈值,cv2.COLOR_GRAY2BGR)