Question

__author__ = 'Kyle'

HELP_MESSAGE = """Script: frame_grabber.py
Usage: python frame_grabber.py path/to/video
Requires: OpenCV 2.4.8+
Purpose: Select and save frames from a given video.
   Commands:
   Key             Function
   a               previous frame
   d               next frame
   q               exit
   SHIFT + a       skip 10 frames forward
   SHIFT + d       skip 10 frames backwards
   s               saves current frame
   dbl click       saves current frame
Controls:
Slider          Navigate through the video
"""

# Check if the user has provided a path to a file
# otherwise display the HELP_MESSAGE

import sys
import time as t

# Check if OpenCV module is present
# otherwise stop the application

try:
    import cv2
except ImportError as e:
    print "Fatal Error: Could not import OpenCV, ", e
   exit(-1)
else:
    print "Using OpenCV ", cv2.__version__

# these flags may depend on your opencv version:
# in opencv 3.0.0 these flags are implemented as
# cv2.CAP_PROP_POS_FRAMES and
# cv2.CAP_PROP_FRAME_COUNT

CURRENT_FRAME_FLAG = cv2.cv.CV_CAP_PROP_POS_FRAMES
TOTAL_FRAMES_FLAG = cv2.cv.CV_CAP_PROP_FRAME_COUNT
WIN_NAME = "Frame Grabber"
POS_TRACKBAR = "pos_trackbar"

#VIDEO_PATH = 'camera13.h264'

  #try:
  #   VIDEO_PATH = sys.argv[1]
  # except IndexError as e:
  #   print HELP_MESSAGE
  #  exit(-1)


    cap = cv2.VideoCapture("camera13.h264")

    if not cap.isOpened():
        print "Fatal Error: Could not open the specified file."
        exit(-1)

ret, frame = cap.read()

if not ret:
    print "Fatal Error: Could not read/decode frames from specified file."
    exit(-1)


def dummy():
    pass


def save_image():
    filename = "image_%0.5f.png" % t.time()
    cv2.imwrite(filename, frame)


def seek_callback(x):
    global frame
    i = cv2.getTrackbarPos(POS_TRACKBAR, WIN_NAME)
    cap.set(CURRENT_FRAME_FLAG, i-1)
    _, frame = cap.read()
    cv2.imshow(WIN_NAME, frame)


def mouse_callback(event,x,y,flags,param):

if event == cv2.EVENT_LBUTTONDBLCLK:
    save_image()


 def skip_frame_generator(df):

     def skip_frame():
          global frame
          cf = cap.get(CURRENT_FRAME_FLAG) - 1
          cap.set(CURRENT_FRAME_FLAG, cf+df)
          cv2.setTrackbarPos(POS_TRACKBAR, WIN_NAME,                  int(cap.get(CURRENT_FRAME_FLAG)))
          _, frame = cap.read()

return skip_frame


cv2.namedWindow(WIN_NAME)
cv2.createTrackbar(POS_TRACKBAR, WIN_NAME, 0,             int(cap.get(TOTAL_FRAMES_FLAG)), seek_callback)
cv2.setMouseCallback(WIN_NAME, mouse_callback)

 actions = dict()

actions[ord("D")] = skip_frame_generator(10)
actions[ord("d")] = skip_frame_generator(1)
actions[ord("a")] = skip_frame_generator(-1)
actions[ord("A")] = skip_frame_generator(-10)
actions[ord("q")] = lambda: exit(0)
actions[ord("s")] = save_image

while True:

    cv2.imshow(WIN_NAME, frame)
    key = cv2.waitKey(0) & 0xFF
    actions.get(key, dummy)()``

执行代码时，我收到错误--OverflowError：Python int太大而无法转换为C long。我怎么能解决这个问题呢？此代码旨在创建一个帧抓取器，允许我选择我想要的帧并保存它。

Answer 1

嗯，错误告诉你你在这一行传递一个数字：

cv2.createTrackbar(POS_TRACKBAR, WIN_NAME, 0,int(cap.get(TOTAL_FRAMES_FLAG)), seek_callback)

这太大了，无法投射到ctypes.c_long;此类型可表示的最大数量为（2 ** 31）-1 = 2147483647.

这可能是你的TOTAL_FRAMES_FLAG。现在有很多帧（大约500天@ 50fps），所以它不对。

我注意到您在打开视频文件之前获得了此值，因此此时可能未定义。在打开文件后尝试执行此操作，看看是否可以解决问题。您也可以打印该值，看看它是否确实太大（在您尝试建议的更改之前）。

如何解决OverflowError：Python int太大而无法使用opencv转换为C long？

1 个答案: