bg_modeling.py

import os 
import time 
import sys 
import cv2 
from utils import resize_image_frame 
 
 
def capture_slides_bg_modeling( 
 video_path, 
 output_dir_path, 
 type_bgsub, 
 history, 
 threshold, 
 MIN_PERCENT_THRESH, 
 MAX_PERCENT_THRESH, 
): 
 print(f"Using {type_bgsub} for Background Modeling...") 
 print("---" * 10) 
 
 if type_bgsub == "GMG": 
 bg_sub = cv2.bgsegm.createBackgroundSubtractorGMG( 
 initializationFrames=history, decisionThreshold=threshold 
 ) 
 elif type_bgsub == "KNN": 
 bg_sub = cv2.createBackgroundSubtractorKNN( 
 history=history, dist2Threshold=threshold, detectShadows=False 
 ) 
 else: 
 raise ValueError("Please choose GMG or KNN as background subtraction method") 
 
 capture_frame = False 
 screenshots_count = 0 
 
 # Capture video frames. 
 cap = cv2.VideoCapture(video_path) 
 
 if not cap.isOpened(): 
 print("Unable to open video file: ", video_path) 
 sys.exit() 
 
 start = time.time() 
 # Loop over subsequent frames. 
 while cap.isOpened(): 
 ret, frame = cap.read() 
 
 if not ret: 
 break 
 
 # Create a copy of the original frame. 
 orig_frame = frame.copy() 
 # Resize the frame keeping aspect ratio. 
 frame = resize_image_frame(frame, resize_width=640) 
 
 # Apply each frame through the background subtractor. 
 fg_mask = bg_sub.apply(frame) 
 
 # Compute the percentage of the Foreground mask." 
 p_non_zero = (cv2.countNonZero(fg_mask) / (1.0 * fg_mask.size)) * 100 
 
 # %age of non-zero pixels < MAX_PERCENT_THRESH, implies motion has stopped. 
 # Therefore, capture the frame. 
 if p_non_zero < MAX_PERCENT_THRESH and not capture_frame: 
 capture_frame = True 
 
 screenshots_count += 1 
 
 png_filename = f"{screenshots_count:03}.jpg" 
 out_file_path = os.path.join(output_dir_path, png_filename) 
 print(f"Saving file at: {out_file_path}") 
 cv2.imwrite(out_file_path, orig_frame, [cv2.IMWRITE_JPEG_QUALITY, 75]) 
 
 # p_non_zero >= MIN_PERCENT_THRESH, indicates motion/animations. 
 # Hence wait till the motion across subsequent frames has settled down. 
 elif capture_frame and p_non_zero >= MIN_PERCENT_THRESH: 
 capture_frame = False 
 
 end_time = time.time() 
 print("***" * 10, "\n") 
 print("Statistics:") 
 print("---" * 10) 
 print(f"Total Time taken: {round(end_time-start, 3)} secs") 
 print(f"Total Screenshots captured: {screenshots_count}") 
 print("---" * 10, "\n") 
 
 # Release Video Capture object. 
 cap.release()