视频处理-按帧或者按秒截取图像

通过帧数间隔截取视频帧

import cv2
 
cap = cv2.VideoCapture("./query_video/test_video_0.mp4")
c = 1
frameRate = 100  # 帧数截取间隔（每隔100帧截取一帧）
 
while(True):
	ret, frame = cap.read()
	if ret:
		if(c % frameRate == 0):
			print("开始截取视频第：" + str(c) + " 帧")
			# 这里就可以做一些操作了：显示截取的帧图片、保存截取帧到本地
			cv2.imwrite("./capture_image/" + str(c) + '.jpg', frame)  # 这里是将截取的图像保存在本地
		c += 1
		cv2.waitKey(0)
	else:
		print("所有帧都已经保存完成")
		break
cap.release()

通过时间间隔截取视频帧

import cv2
cap = cv2.VideoCapture("./query_video/test_video_0.mp4")
c = 1
timeRate = 10  # 截取视频帧的时间间隔（这里是每隔10秒截取一帧）
 
while(True):
	ret, frame = cap.read()
	FPS = cap.get(5)
	if ret:
		frameRate = int(FPS) * timeRate  # 因为cap.get(5)获取的帧数不是整数，所以需要取整一下（向下取整用int，四舍五入用round，向上取整需要用math模块的ceil()方法）
		if(c % frameRate == 0):
			print("开始截取视频第：" + str(c) + " 帧")
			# 这里就可以做一些操作了：显示截取的帧图片、保存截取帧到本地
			cv2.imwrite("./capture_image/" + str(c) + '.jpg', frame)  # 这里是将截取的图像保存在本地
		c += 1
		cv2.waitKey(0)
	else:
		print("所有帧都已经保存完成")
		break
cap.release()

cap = cv2.VideoCapture 的属性

get方法参数按顺序对应下表（从0开始编号

propId –

Property identifier. It can be one of the following:

• CV_CAP_PROP_POS_MSEC Current position of the video file in milliseconds or video capture timestamp.
• CV_CAP_PROP_POS_FRAMES 0-based index of the frame to be decoded/captured next.
• CV_CAP_PROP_POS_AVI_RATIO Relative position of the video file: 0 - start of the film, 1 - end of the film.
• CV_CAP_PROP_FRAME_WIDTH Width of the frames in the video stream.
• CV_CAP_PROP_FRAME_HEIGHT Height of the frames in the video stream.
• CV_CAP_PROP_FPS Frame rate.
• CV_CAP_PROP_FOURCC 4-character code of codec.
• CV_CAP_PROP_FRAME_COUNT Number of frames in the video file.
• CV_CAP_PROP_FORMAT Format of the Mat objects returned by retrieve() .
• CV_CAP_PROP_MODE Backend-specific value indicating the current capture mode.
• CV_CAP_PROP_BRIGHTNESS Brightness of the image (only for cameras).
• CV_CAP_PROP_CONTRAST Contrast of the image (only for cameras).
• CV_CAP_PROP_SATURATION Saturation of the image (only for cameras).
• CV_CAP_PROP_HUE Hue of the image (only for cameras).
• CV_CAP_PROP_GAIN Gain of the image (only for cameras).
• CV_CAP_PROP_EXPOSURE Exposure (only for cameras).
• CV_CAP_PROP_CONVERT_RGB Boolean flags indicating whether images should be converted to RGB.
• CV_CAP_PROP_WHITE_BALANCE_U The U value of the whitebalance setting (note: only supported by DC1394 v 2.x backend currently)
• CV_CAP_PROP_WHITE_BALANCE_V The V value of the whitebalance setting (note: only supported by DC1394 v 2.x backend currently)
• CV_CAP_PROP_RECTIFICATION Rectification flag for stereo cameras (note: only supported by DC1394 v 2.x backend currently)
• CV_CAP_PROP_ISO_SPEED The ISO speed of the camera (note: only supported by DC1394 v 2.x backend currently)
• CV_CAP_PROP_BUFFERSIZE Amount of frames stored in internal buffer memory (note: only supported by DC1394 v 2.x backend currently)

最后

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