Question

我正在研究一个项目，在该项目中，必须使用鼠标单击选择一个对象，然后找到该对象与相机之间的距离。

这是我的代码：

import numpy as np
import cv2
from imutils.video import VideoStream
import argparse
import imutils
import time
import datetime


def find_marker(image):
    # convert the image to grayscale, blur it, and detect edges
    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    gray = cv2.GaussianBlur(gray, (5, 5), 0)
    edged = cv2.Canny(gray, 35, 125)

    # find the contours in the edged image and keep the largest one;
    # we'll assume that this is our piece of paper in the image
    _, cnts, _ = cv2.findContours(edged.copy(), cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
    c = max(cnts, key=cv2.contourArea)

    # compute the bounding box of the of the paper region and return it
    return cv2.minAreaRect(c)


def distance_to_camera(knownWidth, focalLength, perWidth):
    # compute and return the distance from the maker to the camera
    return (knownWidth * focalLength) / perWidth


# initialize the known distance from the camera to the object, which
#, in this case, is 24 inches
KNOWN_DISTANCE = 24.0

# initialize the known object width, which in this case, the piece of
# paper is 12 inches wide
KNOWN_WIDTH = 11.0

ap = argparse.ArgumentParser()
ap.add_argument("-v", "--video",
    help="path to the (optional) video file")
args = vars(ap.parse_args())

# if the video path was not supplied, grab the reference to the
# camera
if not args.get("video", False):
    vs = VideoStream(src=0).start()
    time.sleep(2.0)

# otherwise, load the video
else:
    vs = cv2.VideoCapture(args["video"])


# loop over the frames from the video stream


frame = vs.read()
marker = find_marker(frame)
# otherwise, load the video

focalLength = (marker[1][0] * KNOWN_DISTANCE) / KNOWN_WIDTH

while (1):
    # grab the frame from the threaded video stream and resize it
    # to have a maximum width of 400 pixels

    frame = vs.read()
    frame = imutils.resize(frame, width=400)

    if frame is None:
        break



    marker = find_marker(frame)
    # image = cv2.imread(frame)


    inches = distance_to_camera(KNOWN_WIDTH, focalLength, marker[1][0])

    # draw a bounding box around the image and display it
    box = np.int0(cv2.boxPoints(marker))
    cv2.drawContours(frame, [box], -1, (0, 255, 0), 2)
    cv2.putText(frame, "%.2fft" % (inches / 12),
                    (frame.shape[1] - 200, frame.shape[0] - 20), cv2.FONT_HERSHEY_SIMPLEX,
                    2.0, (0, 255, 0), 3)
    timestamp = datetime.datetime.now()
    ts = timestamp.strftime("%A %d %B %Y %I:%M:%S%p")
    cv2.putText(frame, ts, (10, frame.shape[0] - 10), cv2.FONT_HERSHEY_SIMPLEX,
                0.35, (0, 0, 255), 1)

    cv2.imshow("Frame", frame)
    key = cv2.waitKey(1) & 0xFF

    # if the `q` key was pressed, break from the loop
    if key == ord("q"):
        break

# do a bit of cleanup
cv2.destroyAllWindows()
vs.stop()

在这段代码中，我能够找到物体距离，但问题是它一次检测多个物体并给出距离。

我想要的是一次选择一个对象，并使用鼠标单击功能在其上获得方形ROI。

有人知道该怎么做吗？

Answer 1

您可以使用setMouseCallback函数检测OpenCV中图像上的鼠标单击。首先，创建一个命名窗口，然后使用该图像调用setMouseCallback函数，并检测鼠标单击。 while循环将连续运行，直到您在键盘上选择“ c”以中断并完成收集点为止。 Xpt和Ypt返回您在图像上单击的位置的x和y像素坐标的列表。如果在错误的位置单击，请按“ r”，它将重置列表并创建一个新图像以单击。

clone = image.copy()
cv2.namedWindow('image you want to click on')
cv2.setMouseCallback('image you want to click on', click_and_extract_points)

while 1:
    cv2.imshow('image', image)
    key = cv2.waitKey(1) & 0xFF

    if key == ord('r'):  # if mouse clicks done incorrectly, press 'r'. Resets arrays and map image.
        Xpt = []
        Ypt = []
        image = clone.copy()

    elif key == ord('c'):
        break

def click_and_extract_points(event, x, y, flags, param):
    if event == cv2.EVENT_LBUTTONDBLCLK:
        Xpt.append(x)
        Ypt.append(y)
        print(Xpt, Ypt)

Answer 2

您可以使用opencv提供的内置功能：

roi = cv2.selectROI(image)

它创建/显示“ ROI选择”窗口，显示框架。使用鼠标选择边界框，将鼠标指针从左上角拖动到右下角。

该函数有几个不需要的参数：

selectROI(windowName, img[, showCrosshair[, fromCenter]]) -> retval

参数windowName进行选择过程的窗口的名称显示。
参数img图片以选择投资回报率。
参数showCrosshair，如果选择矩形的真实十字准线为显示。
参数fromCenter，如果选择的真实中心将与初始鼠标匹配位置。在相反的情况下，选择矩形的一个角将对应于鼠标的初始位置。

返回选择的ROI或如果选择被取消则为空矩形。

控件：使用space或enter完成选择，使用键c取消选择。

重载函数不需要windowName。

selectROI(img[, showCrosshair[, fromCenter]]) -> retval

如何在视频帧中单击鼠标并选择一个对象？

2 个答案: