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我想在視頻中定義一個感興趣區域并只處理該區域

Python

幕布斯6054654 2022-01-11 17:20:44

我在理解 opencv 感興趣的區域時遇到問題。我有一些代碼可以從我的first_frame. 我還可以用我的mouse_draw_rect函數繪制一個矩形?，F在，我希望背景減法只發生在我繪制的矩形內，因為我想加快算法處理速度。我知道我必須設置某種感興趣的區域，但我昨天和今天都嘗試了，但我從教程中嘗試過的都沒有奏效。有人可以幫助指導我完成這個過程嗎？編輯：試圖修復代碼import numpy as npimport cv2import matplotlib.pyplot as pltcap = cv2.VideoCapture(0)_, first_frame = cap.read()def mouse_draw_rect(event, x, y, flags, params): global point1, point2, drawing, first_frame, x1, x2, y1, y2 if event == cv2.EVENT_LBUTTONDOWN: if drawing is False: drawing = True point1 = (x, y) x1 = (x) y1 = (y) else: drawing = False elif event == cv2.EVENT_MOUSEMOVE: if drawing is True: point2 = (x, y) x2 = (x) y2 = (y) elif event == cv2.EVENT_MBUTTONDOWN: first_frame = framedrawing = Falsepoint1 = ()point2 = ()x1 = ()x2 = ()y1 = ()y2 = ()cv2.namedWindow('Original')cv2.setMouseCallback("Original", mouse_draw_rect)while True: ret, frame = cap.read( ) if point1 and point2: cv2.rectangle(frame, point1, point2, (0, 0, 0),5) difference = cv2.absdiff(first_frame[y1:y2, x1:x2], frame[y1:y2, x1:x2]) difference = cv2.GaussianBlur(difference, (3, 3), 0) _, difference = cv2.threshold(difference, 18, 255, cv2.THRESH_BINARY) cv2.imshow('first frame (1)', first_frame) cv2.imshow('Original', frame) cv2.imshow('difference', difference) key = cv2.waitKey(30) & 0xff if key == 27: breakcap.release()cv2.destroyAllWindows()

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2 回答

開滿天機

TA貢獻1786條經驗獲得超13個贊

只需按您繪制的矩形區域進行裁剪。代替

difference = cv2.absdiff(first_frame, frame)

利用

difference = cv2.absdiff(first_frame[y1:y2, x1:x2], frame[y1:y2, x1:x2])

反對回復 2022-01-11

萬千封印

TA貢獻1891條經驗獲得超3個贊

主要問題在于 ROI 選擇事件以及當前如何調用它。當前的實現不是動態的，這意味著我們無法可視化我們正在嘗試選擇的 ROI。此外，我們甚至在選擇 ROI 之前就已經開始處理。

選擇 ROI 的正確方法是，一旦我們捕獲了第一幀，注冊鼠標單擊事件并無限期地可視化該幀imshow，waitKey(n)直到按下某個特定鍵?；蛘?，我們可以通過使用waitKey(0)（未測試）在沒有無限循環的情況下實現相同的效果。

在這個階段，我們應該能夠繪制出想要的 ROI 矩形。這里的關鍵因素是必須通過使用無限循環或waitKey(0). 僅僅注冊活動是不夠的。完成 ROI 選擇后，繼續執行其余代碼。

一些建議如下：

盡可能避免使用全局變量
為 ROI 選擇創建單獨的窗口，然后將其丟棄
為每個單獨的任務創建單獨的函數

以下是演示正確使用鼠標單擊事件來選擇視頻處理的 ROI 的完整代碼：

import numpy as np

import cv2

import matplotlib.pyplot as plt

ORIGINAL_WINDOW_TITLE = 'Original'

FIRST_FRAME_WINDOW_TITLE = 'First Frame'

DIFFERENCE_WINDOW_TITLE = 'Difference'

canvas = None

drawing = False # true if mouse is pressed

#Retrieve first frame

def initialize_camera(cap):

_, frame = cap.read()

return frame

# mouse callback function

def mouse_draw_rect(event,x,y,flags, params):

global drawing, canvas

if drawing:

canvas = params[0].copy()

if event == cv2.EVENT_LBUTTONDOWN:

drawing = True

params.append((x,y)) #Save first point

elif event == cv2.EVENT_MOUSEMOVE:

if drawing:

cv2.rectangle(canvas, params[1],(x,y),(0,255,0),2)

elif event == cv2.EVENT_LBUTTONUP:

drawing = False

params.append((x,y)) #Save second point

cv2.rectangle(canvas,params[1],params[2],(0,255,0),2)

def select_roi(frame):

global canvas

canvas = frame.copy()

params = [frame]

ROI_SELECTION_WINDOW = 'Select ROI'

cv2.namedWindow(ROI_SELECTION_WINDOW)

cv2.setMouseCallback(ROI_SELECTION_WINDOW, mouse_draw_rect, params)

roi_selected = False

while True:

cv2.imshow(ROI_SELECTION_WINDOW, canvas)

key = cv2.waitKey(10)

#Press Enter to break the loop

if key == 13:

break;

cv2.destroyWindow(ROI_SELECTION_WINDOW)

roi_selected = (3 == len(params))

if roi_selected:

p1 = params[1]

p2 = params[2]

if (p1[0] == p2[0]) and (p1[1] == p2[1]):

roi_selected = False

#Use whole frame if ROI has not been selected

if not roi_selected:

print('ROI Not Selected. Using Full Frame')

p1 = (0,0)

p2 = (frame.shape[1] - 1, frame.shape[0] -1)

return roi_selected, p1, p2

if __name__ == '__main__':

cap = cv2.VideoCapture(0)

#Grab first frame

first_frame = initialize_camera(cap)

#Select ROI for processing. Hit Enter after drawing the rectangle to finalize selection

roi_selected, point1, point2 = select_roi(first_frame)

#Grab ROI of first frame

first_frame_roi = first_frame[point1[1]:point2[1], point1[0]:point2[0], :]

#An empty image of full size just for visualization of difference

difference_image_canvas = np.zeros_like(first_frame)

while cap.isOpened():

ret, frame = cap.read()

if ret:

#ROI of current frame

roi = frame[point1[1]:point2[1], point1[0]:point2[0], :]

difference = cv2.absdiff(first_frame_roi, roi)

difference = cv2.GaussianBlur(difference, (3, 3), 0)

_, difference = cv2.threshold(difference, 18, 255, cv2.THRESH_BINARY)

#Overlay computed difference image onto the whole image for visualization

difference_image_canvas[point1[1]:point2[1], point1[0]:point2[0], :] = difference.copy()

cv2.imshow(FIRST_FRAME_WINDOW_TITLE, first_frame)

cv2.imshow(ORIGINAL_WINDOW_TITLE, frame)

cv2.imshow(DIFFERENCE_WINDOW_TITLE, difference_image_canvas)

key = cv2.waitKey(30) & 0xff

if key == 27:

break

else:

break

cap.release()

cv2.destroyAllWindows()

專業提示：有時，在初始化相機時，根據房間內的環境光，它需要一些時間來預熱。您可以考慮跳過一些初始幀，讓相機從初始化階段穩定下來?？梢酝ㄟ^initialize_camera在上述代碼中定義函數來完成，如下所示：

def initialize_camera(cap):

for i in range(0,60): #Skip first 60 frames

_, frame = cap.read()

return frame

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我想在視頻中定義一個感興趣區域并只處理該區域

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