在网络摄像头视频上创建多个投资回报率

Question

我正在尝试通过我的网络摄像头流创建多个 ROI。我使用了这个名为 roipoly (https://github.com/jdoepfert/roipoly.py)

的库

我修改了示例代码 (examples/multi_roi_example.py) 以在网络摄像头上工作，现在看起来像这样

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()

但问题是在绘制 ROI 后，视频流保持暂停状态，永远不会继续。如何恢复网络摄像头流及其之上的 ROI

Answer 1

我发现问题很少。

主要问题是 plt.show() 一直等到您关闭 window，这会阻塞其余代码。

它需要 plt.show(block=False)，这也需要 plt.pause(0.001)，所以它有时间在 window 中更新图像。

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

另一个问题是你在每个循环中运行 ROI - 所以你必须在 selecting

之后使用一些布尔变量来跳过它

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 ...

或者您应该 select 循环前的投资回报率

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 ...

另一个问题是 waitKey，只有当您使用 cv2.imshow(...) 显示图像时才有效，但您不使用它，因此 waitKey 将无法获取密钥。

另一个问题是 cv2 给出颜色图像 BGR 但 matplotlib 需要 RGB - 所以你必须转换它。

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

完整的工作代码：

带布尔变量的版本 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)

循环前有 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)

顺便说一句： 如果你需要矩形 ROI 那么有 cv2.selectROI() 到 select 一个区域和 cv2.cv2.selectROIs() 到 select许多地区

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

并且它不需要从 BGR 转换为 RGB。

在网络摄像头视频上创建多个投资回报率

Creating multiple ROI on webcam video

python

opencv

matplotlib

roi