blog_main.py

#!/bin/python

__author__ = 'Giuseppe Battista'
__url__ = 'http://giusedroid.blogspot.com'

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

More info: http://giusedroid.blogspot.com
"""

# 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 = None

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


cap = cv2.VideoCapture(VIDEO_PATH)

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)()