使用Python中的Watchdog处理图像

Question

我正在使用监视程序库来检测何时在特定文件夹中创建新映像。 当看门狗检测到新创建的图像时，我使用SimpleCV / OpenCV启动了一些图像处理功能。

但是，图片是从Raspberry Pi相机拍摄的，从下面的错误中我不相信整个图像首次出现在目录中时会被保存。 （基本上，文件以“片段”或多种形式保存）。

请注意 ，当我将图像复制并粘贴到相应的文件夹中时，脚本会成功运行。

问：有没有办法在整个文件保存后启动图像处理？

import time
from SimpleCV import Image
from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler

class ExampleHandler(FileSystemEventHandler):
    def on_created(self, event):
        image = Image(event.src_path)
        do image processing stuff
        print "Got event for file %s" % event.src_path 

observer = Observer()
event_handler = ExampleHandler() # create event handler
observer.schedule(event_handler, path='/path/to/images') # set observer to use created handler in directory
observer.start()

# sleep until keyboard interrupt, then stop + rejoin the observer
try:
    while True:
        time.sleep(1)
except KeyboardInterrupt:
    observer.stop()

observer.join()

错误转储：

Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 552, in __bootstrap_inner
    self.run()
  File "/usr/local/lib/python2.7/dist-packages/watchdog/observers/api.py", line 241, in run
    self.dispatch_events(self.event_queue, self.timeout)
  File "/usr/local/lib/python2.7/dist-packages/watchdog/observers/api.py", line 408, in dispatch_events
    self._dispatch_event(event, watch)
  File "/usr/local/lib/python2.7/dist-packages/watchdog/observers/api.py", line 403, in _dispatch_event
    handler.dispatch(event)
  File "/usr/local/lib/python2.7/dist-packages/watchdog/events.py", line 361, in dispatch
    _method_map[event_type](event)
  File "picture_classifier_cube.py", line 11, in on_created
    image = Image(event.src_path)
  File "/usr/local/lib/python2.7/dist-packages/SimpleCV/ImageClass.py", line 1073, in __init__
    self._pil = pil.open(self.filename).convert("RGB")
  File "/usr/lib/python2.7/dist-packages/PIL/Image.py", line 1980, in open
    raise IOError("cannot identify image file")
IOError: cannot identify image file

编辑在识别新文件后更新处理程序以休眠几秒钟后，我收到一个不同的错误。

class ExampleHandler(FileSystemEventHandler):
    def on_created(self, event):
        time.sleep(3)
        cans = Image(event.src_path)

错误

IOError: [Errno 2] No such file or directory: '/path/to/images/test.jpg~'

请注意，我使用以下Pi命令捕获图像： raspistill -o 'test.jpg'

Answer 1

虽然可能无法确定文件是否已完成写入而未修改执行写入的程序，但您可以监视文件大小：

from os import stat
from time import sleep

def wait_for_write_finish( filename ):
    last_size, size= -1, 0
    while size!=last_size:
        sleep(1)
        last_size, size= size, stat(filename).st_size

您可能希望通过适当的线程执行此操作