参考《Learning OpenCV 3 Computer Vision with Python second Edition》Chapter 2
目录结构
# -*-coding:utf-8-*-
# managers.py
import cv2
import numpy as np
import time
class CaptureManager(object):
def __init__(self, capture, preview_window_manager=None, should_mirror_preview=False):
self.preview_window_manager = preview_window_manager
self.should_mirror_preview = should_mirror_preview
self._capture = capture
# 给多头摄像机使用
self._channel = 0
# 标识是否已经grab()
self._entered_frame = False
self._frame = None
self._image_file_name = None
self._video_file_name = None
self._video_encoding = None
self._video_writer = None
# 用于计算帧率
self._start_time = None
# 已处理过的frame个数
self._frames_elapsed = 0
# 估算的帧率，保存视频且无法获取当前帧率时使用
self._fps_estimate = None
@property
def channel(self):
return self._channel
@channel.setter
def channel(self, value):
if self._channel != value:
self._channel = value
self._frame = None
@property
def frame(self):
if self._entered_frame and self._frame is None:
_, self._frame = self._capture.retrieve()
return self._frame
@frame.setter
def frame(self, processed_frame):
if processed_frame is not None:
self._frame = processed_frame
@property
def is_writing_image(self):
return self._image_file_name is not None
@property
def is_writing_video(self):
return self._video_file_name is not None
# 调用capture.grab()
def enter_frame(self):
assert not self._entered_frame, "上一个enter_frame()没有与之对应的exit_frame()"
if self._capture is not None:
self._entered_frame = self._capture.grab()
# 真正保存帧的地方
def exit_frame(self):
if self.frame is None:
self._entered_frame = False
return
# 如果是第一帧，记录开始时间
if self._frames_elapsed == 0:
self._start_time = time.time()
# 否则计算帧率
else:
time_elapsed = time.time() - self._start_time
self._fps_estimate = self._frames_elapsed / time_elapsed
self._frames_elapsed += 1
# 如果windowManager不为空，则显示帧
if self.preview_window_manager is not None:
if self.should_mirror_preview:
mirrored_frame = np.fliplr(self._frame).copy()
self.preview_window_manager.show(mirrored_frame)
else:
self.preview_window_manager.show(self._frame)
if self.is_writing_image:
cv2.imwrite(self._image_file_name, self._frame)
self._image_file_name = None
self._write_video_frame()
self._frame = None
self._entered_frame = False
# 记录保存图像的文件名
def write_image(self, filename):
self._image_file_name = filename
# 记录保存视频的文件名和编码信息
def start_writing_video(self, filename, encoding=cv2.VideoWriter_fourcc('X', 'V', 'I', 'D')):
self._video_file_name = filename
self._video_encoding = encoding
# 清除保存视频的信息
def stop_writing_video(self):
self._video_file_name = None
self._video_encoding = None
self._video_writer = None
# 写视频帧的地方
def _write_video_frame(self):
if not self.is_writing_video:
return
if self._video_writer is None:
fps = self._capture.get(cv2.CAP_PROP_FPS)
if fps == 0.0:
if self._frames_elapsed < 20:
return
else:
fps = self._fps_estimate
size = (int(self._capture.get(cv2.CAP_PROP_FRAME_WIDTH)), int(self._capture.get(cv2.CAP_PROP_FRAME_HEIGHT)))
self._video_writer = cv2.VideoWriter(self._video_file_name, self._video_encoding, fps, size)
self._video_writer.write(self._frame)
class WindowManager(object):
def __init__(self, window_name, keypress_callback=None):
self.keypress_callback = keypress_callback
self._window_name = window_name
self._is_window_created = False
@property
def is_window_created(self):
return self._is_window_created
def create_window(self):
cv2.namedWindow(self._window_name)
self._is_window_created = True
def show(self, frame):
cv2.imshow(self._window_name, frame)
def destroy_window(self):
cv2.destroyWindow(self._window_name)
self._is_window_created = False
def process_events(self):
keycode = cv2.waitKey(1)
if self.keypress_callback is not None and keycode != -1:
keycode &= 0xFF
self.keypress_callback(keycode)
# -*-coding:utf-8-*-
# scratch.py
import cv2
from cvgui.managers import WindowManager, CaptureManager
class Scratch(object):
def __init__(self, video):
self._window_manager = WindowManager('Scratch', self.on_keypress)
self._capture_manager = CaptureManager(cv2.VideoCapture(video), self._window_manager, True)
def run(self):
self._window_manager.create_window()
while self._window_manager.is_window_created:
self._capture_manager.enter_frame()
frame = self._capture_manager.frame
if frame is not None:
processed_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# TODO 对frame进行其他处理
self._capture_manager.frame = processed_frame
self._capture_manager.exit_frame()
self._window_manager.process_events()
def on_keypress(self, keycode):
"""
space -> 截屏
tab -> 开始/结束录屏
escape -> 退出
"""
if keycode == 32: # space
self._capture_manager.write_image('screenshot.png')
elif keycode == 9: # tab
if not self._capture_manager.is_writing_video:
self._capture_manager.start_writing_video('screencast.avi')
else:
self._capture_manager.stop_writing_video()
elif keycode == 27: # esc
self._window_manager.destroy_window()
if __name__ == "__main__":
Scratch("street.mp4").run()
效果
网友评论