video_to_pdf.py

import os
import time
import cv2
import imutils
import shutil
import img2pdf
import glob
from skimage.metrics import structural_similarity

OUTPUT_SLIDES_DIR = f"./output"

FRAME_RATE = 1                   # no.of frames per second that needs to be processed, fewer the count faster the speed
WARMUP = FRAME_RATE              # initial number of frames to be skipped
FGBG_HISTORY = FRAME_RATE * 15   # no.of frames in background object
VAR_THRESHOLD = 16               # Threshold on the squared Mahalanobis distance between the pixel and the model to decide whether a pixel is well described by the background model.
DETECT_SHADOWS = False            # If true, the algorithm will detect shadows and mark them.
MIN_PERCENT = 0.1                # min % of diff between foreground and background to detect if motion has stopped
MAX_PERCENT = 3                  # max % of diff between foreground and background to detect if frame is still in motion
SSIM_THRESHOLD = 0.9             # SSIM threshold of two consecutive frame



def get_frames(video_path):
    '''A fucntion to return the frames from a video located at video_path
    this function skips frames as defined in FRAME_RATE'''
    
    
    # open a pointer to the video file initialize the width and height of the frame
    vs = cv2.VideoCapture(video_path)
    if not vs.isOpened():
        raise Exception(f'unable to open file {video_path}')


    total_frames = vs.get(cv2.CAP_PROP_FRAME_COUNT)
    frame_time = 0
    frame_count = 0

    # loop over the frames of the video
    while True:
        vs.set(cv2.CAP_PROP_POS_MSEC, frame_time * 1000)    # move frame to a timestamp
        frame_time += 1/FRAME_RATE

        (_, frame) = vs.read()
        # if the frame is None, then we have reached the end of the video file
        if frame is None:
            break

        frame_count += 1
        yield frame_count, frame_time, frame

    vs.release()
 


def detect_unique_screenshots(video_path, output_folder_screenshot_path):
    '''Extract unique screenshots from video'''
    fgbg = cv2.createBackgroundSubtractorMOG2(history=FGBG_HISTORY, varThreshold=VAR_THRESHOLD,detectShadows=DETECT_SHADOWS)

    captured = False
    start_time = time.time()
    (W, H) = (None, None)

    # Get total frames for progress calculation
    cap = cv2.VideoCapture(video_path)
    cap.release()

    screenshoots_count = 0
    last_screenshot = None
    saved_files = []
    
    
    for frame_count, frame_time, frame in get_frames(video_path):
        
        orig = frame.copy()
        frame = imutils.resize(frame, width=600)
        mask = fgbg.apply(frame)

        if W is None or H is None:
            (H, W) = mask.shape[:2]

        p_diff = (cv2.countNonZero(mask) / float(W * H)) * 100

        if p_diff < MIN_PERCENT and not captured and frame_count > WARMUP:
            captured = True
            filename = f"{screenshoots_count:03}_{round(frame_time/60, 2)}.png"
            path = os.path.join(output_folder_screenshot_path, filename)

            image_ssim = 0.0
            if last_screenshot is not None:
                image_ssim = structural_similarity(last_screenshot, orig, channel_axis=2, data_range=255)

            if image_ssim < SSIM_THRESHOLD:
                try:
                    print("saving {}".format(path))
                    cv2.imwrite(str(path), orig)
                    last_screenshot = orig
                    saved_files.append(path)
                    screenshoots_count += 1
                except Exception as e:
                    print(f"Error saving image: {str(e)}")
                    continue

        elif captured and p_diff >= MAX_PERCENT:
            captured = False

    print(f'{screenshoots_count} screenshots Captured!')
    print(f'Time taken {time.time()-start_time}s')
    return saved_files


def initialize_output_folder(video_path):
    '''Clean the output folder if already exists'''
    # Create a safe folder name from video filename
    video_filename = os.path.splitext(os.path.basename(video_path))[0]
    # Replace potentially problematic characters
    safe_filename = "".join(x for x in video_filename if x.isalnum() or x in (' ', '-', '_'))
    output_folder_screenshot_path = os.path.join(OUTPUT_SLIDES_DIR, safe_filename)

    if os.path.exists(output_folder_screenshot_path):
        shutil.rmtree(output_folder_screenshot_path)

    os.makedirs(output_folder_screenshot_path, exist_ok=True)
    print('initialized output folder', output_folder_screenshot_path)
    return output_folder_screenshot_path


def convert_screenshots_to_pdf(video_path, output_folder_screenshot_path):
    # Create a safe filename
    video_filename = os.path.splitext(os.path.basename(video_path))[0]
    safe_filename = "".join(x for x in video_filename if x.isalnum() or x in (' ', '-', '_'))
    output_pdf_path = os.path.join(OUTPUT_SLIDES_DIR, f"{safe_filename}.pdf")
    
    try:
        print('output_folder_screenshot_path', output_folder_screenshot_path)
        print('output_pdf_path', output_pdf_path)
        print('converting images to pdf..')
        
        # Get all PNG files and ensure they exist
        png_files = sorted(glob.glob(os.path.join(output_folder_screenshot_path, "*.png")))
        if not png_files:
            raise Exception("No PNG files found to convert to PDF")
            
        with open(output_pdf_path, "wb") as f:
            f.write(img2pdf.convert(png_files))
            
        print('Pdf Created!')
        print('pdf saved at', output_pdf_path)
        return output_pdf_path
    except Exception as e:
        print(f"Error creating PDF: {str(e)}")
        raise


def video_to_slides(video_path):
    output_folder_screenshot_path = initialize_output_folder(video_path)
    saved_files = detect_unique_screenshots(video_path, output_folder_screenshot_path)
    return output_folder_screenshot_path, saved_files


def slides_to_pdf(video_path, output_folder_screenshot_path, saved_files):
    video_filename = os.path.splitext(os.path.basename(video_path))[0]
    safe_filename = "".join(x for x in video_filename if x.isalnum() or x in (' ', '-', '_'))
    output_pdf_path = os.path.join('uploads', f"{safe_filename}.pdf")
    
    try:
        print('output_folder_screenshot_path', output_folder_screenshot_path)
        print('output_pdf_path', output_pdf_path)
        
        if not saved_files:
            raise Exception("未从视频中捕获到截图")
            
        existing_files = [f for f in saved_files if os.path.exists(f)]
        if not existing_files:
            raise Exception("未找到保存的截图文件")
            
        with open(output_pdf_path, "wb") as f:
            f.write(img2pdf.convert(existing_files))

        print('PDF创建成功！')
        print('PDF保存位置:', output_pdf_path)
        return output_pdf_path
    except Exception as e:
        print(f"创建PDF时出错: {str(e)}")
        raise