在網路攝像頭視頻上創建多個ROI

我試圖通過我的網路攝像頭流創建多個 ROI。我使用了這個名為 roipoly 的庫（https://github.com/jdoepfert/roipoly.py）

我修改了示例代碼 (examples/multi_roi_example.py) 以在 webcam 上作業，現在看起來像這樣

import logging
import cv2
import numpy as np
from matplotlib import pyplot as plt

from roipoly import MultiRoi

logging.basicConfig(format='%(levelname)s ''%(processName)-10s : %(asctime)s '
                           '%(module)s.%(funcName)s:%(lineno)s %(message)s',
                    level=logging.INFO)

cap = cv2.VideoCapture(1)

while cap.isOpened():

# Create image
    val,img =cap.read()

#img = np.ones((100, 100)) * range(0, 100)

# Show the image
    fig = plt.figure()
    plt.imshow(img, interpolation='nearest', cmap="Greys")
    plt.title("Click on the button to add a new ROI")

# Draw multiple ROIs
    multiroi_named = MultiRoi(roi_names=['My first ROI', 'My second ROI'])

# Draw all ROIs
    plt.imshow(img, interpolation='nearest', cmap="Greys")
    roi_names = []
    for name, roi in multiroi_named.rois.items():
        roi.display_roi()
        roi.display_mean(img)
        roi_names.append(name)
    plt.legend(roi_names, bbox_to_anchor=(1.2, 1.05))
    plt.show()
    # Let OpenCV manage window events
    key = cv2.waitKey(50)
    # If ESCAPE key pressed, stop
    if key == 27:
        cap.release()

但問題是，在繪制 ROI 之后，視頻流仍然暫停并且永遠不會繼續。如何恢復網路攝像頭流及其頂部的 ROI

uj5u.com熱心網友回復：

我看到幾個問題。

主要問題是plt.show()等待關閉視窗，這會阻塞其余代碼。

它需要plt.show(block=False)并且這也需要，plt.pause(0.001)因此它有時間更新視窗中的影像。

    plt.show(block=False)    
    plt.pause(0.001)

另一個問題是您在每個回圈中都運行 ROI - 因此您必須在選擇后使用一些布爾變數來跳過它

select_roi = True

while cap.isOpened():

    # ... code ...

    if select_roi:
        fig = plt.figure()
        plt.imshow(img, interpolation='nearest', cmap="Greys")
        plt.title("Click on the button to add a new ROI")

        # Draw multiple ROIs
        multiroi_named = MultiRoi(roi_names=['My first ROI', 'My second ROI'])
        
        select_roi = False  

    # ... code ...

或者您應該在回圈之前選擇 ROI

fig = plt.figure()
plt.imshow(img, interpolation='nearest', cmap="Greys")
plt.title("Click on the button to add a new ROI")

# Draw multiple ROIs
multiroi_named = MultiRoi(roi_names=['My first ROI', 'My second ROI'])

while cap.isOpened():

     # ... code ...

其他問題是waitKey僅當您顯示影像cv2.imshow(...)但您不使用它時才有效，因此waitKey不會獲得密鑰。

另一個問題是 cv2 以顏色提供影像BGR但matplotlib需要RGB- 所以你必須轉換它。

img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

完整的作業代碼：

帶有布爾變數的版本select_roi

import cv2
from matplotlib import pyplot as plt
from roipoly import MultiRoi

#cap = cv2.VideoCapture(0)  # my built-in webcam
cap = cv2.VideoCapture(1)

select_roi = True   # default value as start

while cap.isOpened():

    val, img = cap.read()

    img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

    if select_roi:
        # Show the image
        fig = plt.figure()
        plt.imshow(img, interpolation='nearest', cmap="Greys")
        plt.title("Click on the button to add a new ROI")

        # Draw multiple ROIs
        multiroi_named = MultiRoi(roi_names=['My first ROI', 'My second ROI'])
        
        select_roi = False
   
    # --- after if ---
 
    # Draw all ROIs
    plt.imshow(img, interpolation='nearest', cmap="Greys")
    
    roi_names = []
    for name, roi in multiroi_named.rois.items():
        roi.display_roi()
        #roi.display_mean(img)
        roi_names.append(name)
        
    plt.legend(roi_names, bbox_to_anchor=(1.2, 1.05))
    plt.show(block=False)    
    plt.pause(0.001)

回圈前具有 ROI 的版本

import cv2
from matplotlib import pyplot as plt
from roipoly import MultiRoi

#cap = cv2.VideoCapture(0)  # my built-in webcam
cap = cv2.VideoCapture(1)

val, img = cap.read()

img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

# Show the image
fig = plt.figure()
plt.imshow(img, interpolation='nearest', cmap="Greys")
plt.title("Click on the button to add a new ROI")

# Draw multiple ROIs
multiroi_named = MultiRoi(roi_names=['My first ROI', 'My second ROI'])

while cap.isOpened():

    val, img = cap.read()

    img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

    # Draw all ROIs
    plt.imshow(img, interpolation='nearest', cmap="Greys")
    
    roi_names = []
    for name, roi in multiroi_named.rois.items():
        roi.display_roi()
        #roi.display_mean(img)
        roi_names.append(name)
        
    plt.legend(roi_names, bbox_to_anchor=(1.2, 1.05))
    plt.show(block=False)    
    plt.pause(0.001)

順便說一句：如果您需要矩形 ROI，則cv2.selectROI()選擇一個區域并cv2.cv2.selectROIs()選擇多個區域

results = cv2.selectROIs('image', img)

并且它不需要從轉換BGR為RGB.

標籤：Python opencv matplotlib 投资回报率

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