utils.py

import cv2
import numpy as np
from PIL import Image, PngImagePlugin, ImageDraw
import json
from datetime import datetime
from cryptography.fernet import Fernet
import base64
import hashlib

class WatermarkProcessor:
    def __init__(self, encryption_key=None):
        """Initialize with optional encryption key"""
        if encryption_key:
            self.fernet = Fernet(encryption_key)
        else:
            key = Fernet.generate_key()
            self.fernet = Fernet(key)

    def to_bin(self, data):
        """Convert data to binary format as string"""
        if isinstance(data, str):
            return ''.join(format(ord(char), '08b') for char in data)
        elif isinstance(data, bytes):
            return ''.join(format(x, '08b') for x in data)
        elif isinstance(data, np.ndarray):
            return [format(i, "08b") for i in data]
        elif isinstance(data, int) or isinstance(data, np.uint8):
            return format(data, "08b")
        else:
            raise TypeError("Type not supported.")

    def create_preview(self, image_path, watermark_text, opacity=0.3):
        """Create a preview of watermark on image"""
        try:
            image = Image.open(image_path)
            txt_layer = Image.new('RGBA', image.size, (255, 255, 255, 0))
            draw = ImageDraw.Draw(txt_layer)
            
            # Calculate text position
            text_width = draw.textlength(watermark_text)
            text_x = (image.width - text_width) // 2
            text_y = image.height // 2
            
            # Add watermark text
            draw.text((text_x, text_y), watermark_text, 
                      fill=(255, 255, 255, int(255 * opacity)))
            
            # Combine layers
            preview = Image.alpha_composite(image.convert('RGBA'), txt_layer)
            return preview
        except Exception as e:
            return None

    def png_encode(self, im_name, extra):
        """Encode watermark using PNG metadata"""
        try:
            im = Image.open(im_name)
            info = PngImagePlugin.PngInfo()
            info.add_text("TXT", extra)
            im.save("test.png", pnginfo=info)
            return "test.png", "Watermark added successfully"
        except Exception as e:
            return im_name, f"Error adding watermark: {str(e)}"

    def encode(self, image_path, watermark_text, metadata=None):
        """Encode watermark using simple LSB steganography with header
        
        헤더(32비트)는 watermark 데이터(UTF-8 문자열)의 길이(문자수)를 이진 문자열로 저장합니다.
        """
        try:
            image = cv2.imread(image_path)
            if image is None:
                raise ValueError("Could not read image file")

            # Prepare watermark data
            data = {
                'text': watermark_text,
                'timestamp': datetime.now().isoformat(),
                'metadata': metadata or {}
            }
            
            # Convert data to string (UTF-8)
            json_str = json.dumps(data, ensure_ascii=False)
            # 헤더: 32비트에 데이터 길이(문자수)를 저장
            data_length = len(json_str)
            header = format(data_length, '032b')
            # 본문: 각 문자를 8비트 이진수로 변환
            body = ''.join(format(ord(char), '08b') for char in json_str)
            binary_data = header + body
            
            # Check capacity
            if len(binary_data) > image.shape[0] * image.shape[1] * 3:
                return image_path, "Error: Image too small for watermark data"

            # Embed data into LSB of each pixel
            data_index = 0
            for i in range(image.shape[0]):
                for j in range(image.shape[1]):
                    for k in range(3):
                        if data_index < len(binary_data):
                            pixel = int(image[i, j, k])
                            # Clear the LSB
                            pixel = pixel & 0xFE
                            # Set the LSB according to our data bit
                            pixel = pixel | (int(binary_data[data_index]) & 1)
                            image[i, j, k] = np.uint8(pixel)
                            data_index += 1
                        else:
                            break
                    if data_index >= len(binary_data):
                        break
                if data_index >= len(binary_data):
                    break

            # Save result image (PNG: lossless)
            output_path = f"watermarked_{datetime.now().strftime('%Y%m%d_%H%M%S')}.png"
            cv2.imwrite(output_path, image)
            return output_path, "Watermark added successfully"
            
        except Exception as e:
            return image_path, f"Error in encoding: {str(e)}"

    def decode(self, image_path):
        """Decode watermark using simple LSB steganography with header
        
        먼저 32비트를 읽어 watermark 데이터의 길이(문자수)를 구한 후, 해당 길이만큼의 데이터를 추출합니다.
        """
        try:
            # PNG 메타데이터 먼저 확인
            try:
                im = Image.open(image_path)
                if "TXT" in im.info:
                    return im.info["TXT"]
            except:
                pass

            image = cv2.imread(image_path)
            if image is None:
                raise ValueError("Could not read image file")

            # 모든 픽셀의 LSB를 읽어 이진 문자열 생성
            binary_data = ''
            for i in range(image.shape[0]):
                for j in range(image.shape[1]):
                    for k in range(3):
                        binary_data += str(image[i, j, k] & 1)

            # 먼저 헤더(32비트)를 읽어 데이터 길이(문자수)를 결정
            header = binary_data[:32]
            data_length = int(header, 2)
            total_bits = data_length * 8
            # 본문 데이터 읽기
            message_bits = binary_data[32:32 + total_bits]
            text = ''
            for i in range(0, len(message_bits), 8):
                byte = message_bits[i:i+8]
                text += chr(int(byte, 2))
            try:
                data = json.loads(text)
                return json.dumps(data, ensure_ascii=False, indent=2)
            except json.JSONDecodeError:
                return text
        except Exception as e:
            return f"Error in decoding: {str(e)}"

    def analyze_quality(self, original_path, watermarked_path):
        """Analyze watermark quality"""
        try:
            original = cv2.imread(original_path)
            watermarked = cv2.imread(watermarked_path)
            
            if original is None or watermarked is None:
                raise ValueError("Could not read image files")
            
            # Calculate PSNR
            mse = np.mean((original - watermarked) ** 2)
            if mse == 0:
                psnr = float('inf')
            else:
                psnr = 20 * np.log10(255.0 / np.sqrt(mse))
            
            # Calculate histogram similarity
            hist_original = cv2.calcHist([original], [0], None, [256], [0, 256])
            hist_watermarked = cv2.calcHist([watermarked], [0], None, [256], [0, 256])
            hist_correlation = cv2.compareHist(hist_original, hist_watermarked, cv2.HISTCMP_CORREL)
            
            # Count modified pixels
            diff = cv2.bitwise_xor(original, watermarked)
            modified_pixels = np.count_nonzero(diff)
            
            report = {
                'psnr': round(psnr, 2),
                'histogram_similarity': round(hist_correlation, 4),
                'modified_pixels': modified_pixels,
                'image_size': original.shape,
                'quality_score': round((psnr / 50) * 100, 2) if psnr != float('inf') else 100
            }
            
            return json.dumps(report, indent=2)
            
        except Exception as e:
            return f"Error in quality analysis: {str(e)}"