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import cv2
import os
import time
import sys
def capture_slides_frame_diff(
video_path, output_dir_path, MIN_PERCENT_THRESH=0.06, ELAPSED_FRAME_THRESH=85
):
prev_frame = None
curr_frame = None
screenshots_count = 0
capture_frame = False
frame_elapsed = 0
# Initialize kernel.
kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (7, 7))
# Capture video frames
cap = cv2.VideoCapture(video_path)
if not cap.isOpened():
print("Unable to open video file: ", video_path)
sys.exit()
success, first_frame = cap.read()
print("Using frame differencing for Background Subtraction...")
print("---" * 10)
start = time.time()
# The 1st frame should always be present in the output directory.
# Hence capture and save the 1st frame.
if success:
# Convert frame to grayscale.
first_frame_gray = cv2.cvtColor(first_frame, cv2.COLOR_BGR2GRAY)
prev_frame = first_frame_gray
screenshots_count += 1
filename = f"{screenshots_count:03}.lpg"
out_file_path = os.path.join(output_dir_path, filename)
print(f"Saving file at: {out_file_path}")
# Save frame.
cv2.imwrite(out_file_path, first_frame, [cv2.IMWRITE_JPEG_QUALITY, 75])
# Loop over subsequent frames.
while cap.isOpened():
ret, frame = cap.read()
if not ret:
break
frame_gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
curr_frame = frame_gray
if (prev_frame is not None) and (curr_frame is not None):
frame_diff = cv2.absdiff(curr_frame, prev_frame)
_, frame_diff = cv2.threshold(frame_diff, 80, 255, cv2.THRESH_BINARY)
# Perform dilation to capture motion.
frame_diff = cv2.dilate(frame_diff, kernel)
# Compute the percentage of non-zero pixels in the frame.
p_non_zero = (cv2.countNonZero(frame_diff) / (1.0 * frame_gray.size)) * 100
if p_non_zero >= MIN_PERCENT_THRESH and not capture_frame:
capture_frame = True
elif capture_frame:
frame_elapsed += 1
if frame_elapsed >= ELAPSED_FRAME_THRESH:
capture_frame = False
frame_elapsed = 0
screenshots_count += 1
filename = f"{screenshots_count:03}.png"
out_file_path = os.path.join(output_dir_path, filename)
print(f"Saving file at: {out_file_path}")
cv2.imwrite(out_file_path, frame)
prev_frame = curr_frame
end_time = time.time()
print("***" * 10, "\n")
print("Statistics:")
print("---" * 5)
print(f"Total Time taken: {round(end_time-start, 3)} secs")
print(f"Total Screenshots captured: {screenshots_count}")
print("---" * 10, "\n")
cap.release()
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