python+opencv实现移动侦测（帧差法）

本文实例为大家分享了python+opencv实现移动侦测的具体代码，供大家参考，具体内容如下

1.帧差法原理

移动侦测即是根据视频每帧或者几帧之间像素的差异，对差异值设置阈值，筛选大于阈值的像素点，做掩模图即可选出视频中存在变化的桢。帧差法较为简单的视频中物体移动侦测，帧差法分为：单帧差、两桢差、和三桢差。随着帧数的增加是防止检测结果的重影。

2.算法思路

文章以截取视频为例进行单帧差法移动侦测

3.python实现代码

def threh(video,save_video,thres1,area_threh): cam = cv2.VideoCapture(video)#打开一个视频 input_fps = cam.get(cv2.CAP_PROP_FPS) ret_val, input_image = cam.read() index=[] images=[] images.append(input_image) video_length = int(cam.get(cv2.CAP_PROP_FRAME_COUNT)) input_image=cv2.resize(input_image,(512,512)) ending_frame = video_length fourcc = cv2.VideoWriter_fourcc(*’XVID’) out = cv2.VideoWriter(save_video,fourcc, input_fps, (512, 512)) gray_lwpCV = cv2.cvtColor(input_image, cv2.COLOR_BGR2GRAY) gray_lwpCV = cv2.GaussianBlur(gray_lwpCV, (21, 21), 0) background=gray_lwpCV# es = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (9, 4)) i = 0 # default is 0 outt=[] while(cam.isOpened()) and ret_val == True and i <2999: ## if i % 2==1: ret_val, input_image = cam.read() input_image=cv2.resize(input_image,(512,512)) gray_lwpCV = cv2.cvtColor(input_image, cv2.COLOR_BGR2GRAY) gray_lwpCV = cv2.GaussianBlur(gray_lwpCV, (21, 21), 0) diff = cv2.absdiff(background, gray_lwpCV) outt.append(diff) #跟着图像变换背景 tem_diff=diff.flatten() tem_ds=pd.Series(tem_diff) tem_per=1-len(tem_ds[tem_ds==0])/len(tem_ds) if (tem_per <0.2 )| (tem_per>0.75): background=gray_lwpCV else: diff = cv2.threshold(diff, thres1, 255, cv2.THRESH_BINARY)[1] ret,thresh = cv2.threshold(diff.copy(),150,255,0) contours, hierarchy = cv2.findContours(thresh,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE) # contours, hierarchy = cv2.findContours(diff.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE) for c in contours: if (cv2.contourArea(c) < area_threh) | (cv2.contourArea(c) >int(512*512*0.3) ) : # 对于矩形区域，只显示大于给定阈值的轮廓（去除微小的变化等噪点） continue (x, y, w, h) = cv2.boundingRect(c) # 该函数计算矩形的边界框 cv2.rectangle(input_image, (x, y), (x+w, y+h), (0, 255, 0), 2) index.append(i) # cv2.imshow(’contours’, input_image) # cv2.imshow(’dis’, diff) out.write(input_image) images.append(input_image) i = i+1 out.release() cam.release() return outt,index,images```##调取函数outt=threh(’new_video.mp4’,’test6.mp4’,25,3000)

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