src/image_utils.py

import os
import cv2
import numpy as np
from tqdm import tqdm

watermark_path = '/app/src/assets/watermark.png'

def precompute_watermark(frame_width, frame_height):
    """
    Precomputes the resized watermark and its alpha mask while preserving its aspect ratio.
    """
    watermark = cv2.imread(watermark_path, cv2.IMREAD_UNCHANGED)
    if watermark is None:
        raise FileNotFoundError(f"Watermark image not found at: {watermark_path}")

    wm_rgb = watermark[:, :, :3]
    wm_alpha = watermark[:, :, 3] / 255.0

    # Compute the watermark dimensions while maintaining aspect ratio
    wm_original_height, wm_original_width = wm_rgb.shape[:2]
    scale = min(frame_width * 0.2 / wm_original_width, frame_height * 0.2 / wm_original_height)
    wm_width = int(wm_original_width * scale)
    wm_height = int(wm_original_height * scale)

    # Resize the watermark and its alpha mask
    wm_resized = cv2.resize(wm_rgb, (wm_width, wm_height))
    wm_alpha_resized = cv2.resize(wm_alpha, (wm_width, wm_height))

    # Calculate watermark position (bottom-right corner)
    x_offset = frame_width - wm_width - 10  # 10 px padding from right
    y_offset = frame_height - wm_height - 10  # 10 px padding from bottom

    return wm_resized, wm_alpha_resized, wm_width, wm_height, x_offset, y_offset

def add_watermark_to_frame(frame, watermark_data):
    """
        Adds a watermark to a single frame while preserving its aspect ratio.
        """
    wm_resized, wm_alpha_resized, wm_width, wm_height, x_offset, y_offset = watermark_data

    # Overlay the watermark
    overlay = frame.copy()
    overlay[y_offset:y_offset + wm_height, x_offset:x_offset + wm_width] = (
            wm_alpha_resized[:, :, None] * wm_resized +
            (1 - wm_alpha_resized[:, :, None]) * overlay[y_offset:y_offset + wm_height, x_offset:x_offset + wm_width]
    ).astype(np.uint8)

    return overlay
    
def add_watermark_to_frames(frames_folder, output_folder):
    """
    Applies a watermark to all frames in `frames_folder` and saves them to `output_folder`.
    """
    os.makedirs(output_folder, exist_ok=True)

    frame_files = sorted([
        f for f in os.listdir(frames_folder)
        if f.lower().endswith(('.jpg', '.png'))
    ], key=lambda x: int(os.path.splitext(x)[0]))

    if not frame_files:
        raise FileNotFoundError("No frames found in the input folder.")

    # Load the first frame to determine frame size
    sample_frame_path = os.path.join(frames_folder, frame_files[0])
    sample_frame = cv2.imread(sample_frame_path)
    if sample_frame is None:
        raise ValueError(f"Could not read sample frame: {sample_frame_path}")

    frame_height, frame_width = sample_frame.shape[:2]
    watermark_data = precompute_watermark(frame_width, frame_height)

    print("💧 Adding watermark to frames...")
    for filename in tqdm(frame_files, desc="Watermarking"):
        input_path = os.path.join(frames_folder, filename)
        output_path = os.path.join(output_folder, filename)

        frame = cv2.imread(input_path)
        if frame is None:
            print(f"⚠️ Could not read frame: {input_path}")
            continue

        watermarked = add_watermark_to_frame(frame, watermark_data)
        cv2.imwrite(output_path, watermarked)

    print(f"✅ Watermarked frames saved to: {output_folder}")