如何在 opencv-python 的单独图像中 select ROI？

Question

我正在使用 python 2.7.13 和 opencv 3.4.0。我有一个带有 2 个绿点的视频流。我正在使用颜色检测来跟踪它们。我需要 select 两个 ROI（感兴趣区域），每个 ROI 将包含一个点，在两个单独的图像中进行进一步处理。我编写了一个程序来检测它们并创建 ROI，但问题是它 select 只有一个区域，而有两个点。另外，它给我错误： “第 47 行，在 cv2.imshow ("area1",area1) NameError: 名称 'area1' 未定义"

但是，如果我用 img=cv2.imread("image.jpg") 替换 img=frame.array 行，那么它可以工作，但只适用于图片。 Here how program works now

import cv2
import numpy as np
from picamera.array import PiRGBArray
from picamera import PiCamera
import time
import sys

lowerBound=np.array([33,80,40])
upperBound=np.array([102,255,255]) #ranges for green color

camera = PiCamera()
camera.rotation = 180
camera.resolution = (320, 240)
camera.framerate = 30
font=cv2.FONT_HERSHEY_SIMPLEX

rawCapture = PiRGBArray(camera, size=(320, 240))

time.sleep(0.1)
kernelOpen=np.ones((5,5))
kernelClose=np.ones((20,20))

for frame in camera.capture_continuous(rawCapture, format="bgr",         use_video_port=True): # capture frames from the camera
    img = frame.array #works only if I change this with img =cv2.imread("image.jpg")
    imgHSV= cv2.cvtColor(img,cv2.COLOR_BGR2HSV)
    mask=cv2.inRange(imgHSV,lowerBound,upperBound)

    maskOpen=cv2.morphologyEx(mask,cv2.MORPH_OPEN,kernelOpen)
    maskClose=cv2.morphologyEx(maskOpen,cv2.MORPH_CLOSE,kernelClose) #apply morphology for greater accuracy
    maskFinal=maskClose
    _, conts, _=cv2.findContours(maskFinal.copy(),cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)

    for i in range(len(conts)):
        x,y,w,h=cv2.boundingRect(conts[i])
        area1=img[y:y+h, x:x+w] #selecting my ROI
        cv2.rectangle(img,(x,y),(x+w,y+h),(0,0,255), 2)
    cv2.imshow("maskClose",maskClose)
    cv2.imshow("maskOpen",maskOpen)
    cv2.imshow("mask",mask)
    cv2.imshow("cam",img)
    cv2.imshow ("area1",area1) #Showing my ROI

    key = cv2.waitKey(1) & 0xFF
    rawCapture.truncate(0)
    if key == ord("q"):
            break

Answer 1

在 for 循环中，您保留 setting/overwriting area1，因此输出将始终只有一张图像。您可以通过将 imshow() 移动到 for 循环中轻松解决此问题。

在您的代码顶部添加：
prevNrOfContours = 0

使用以下代码更改帧循环：

    # create a window for each roi
    nrOfContours = len(conts)
    for i in range(nrOfContours):
        x,y,w,h=cv2.boundingRect(conts[i])
        area=img[y:y+h, x:x+w] #selecting my ROI
        cv2.rectangle(img,(x,y),(x+w,y+h),(0,0,255), 2)
        cv2.imshow("area" + str(i), area)

    # if there are more open windows then roi's
    # then close the windows that will not be refreshed
    if prevNrOfContours > nrOfContours:
        for i in range(nrOfContours, prevNrOfContours):
            cv2.destroyWindow("area" + str(i))

    # store the number of roi's in this frame, so it can 
    # be used in the next frame
    prevNrOfContours = nrOfContours

编辑：扩展代码以删除不必要的已打开 windows

Edit2：仅 select 2 个最大的轮廓：

    # instantiate list
    contour_list = []

    for cnt in contours:
            # get contour size
            area = cv2.contourArea(cnt)
            # add tuple of the contour and its size to the list
            contour_list.append((cnt, area))

    # sort list on size
    sorted_list = sorted(contour_list, key=lambda x: x[1])
    # create a window for the 2 largest contours
    for i in range(-2,0):
            x,y,w,h=cv2.boundingRect(sorted_list[i][0])
            roi=img[y:y+h, x:x+w] #selecting my ROI
            cv2.rectangle(img,(x,y),(x+w,y+h),(0,0,255), 2)
            cv2.imshow("area" + str(i), roi)

如何在 opencv-python 的单独图像中 select ROI？

How can I select ROI in a separate image in opencv-python?

python

opencv

roi

object-detection