【python PIL】数字水印添加以及检测

要在图片上添加数字水印，可以使用Python的PIL库（Python Imaging Library），具体步骤如下：

1.导入PIL库

from PIL import Image, ImageDraw, ImageFont

2.打开图片

im = Image.open('image.jpg')

3.创建字体对象

font = ImageFont.truetype('arial.ttf', size=20)

4.创建Draw对象

draw = ImageDraw.Draw(im)

5.添加水印

draw.text((0, 0), '123', fill=(255, 0, 0), font=font)

6.保存图片

im.save('watermark.jpg')

为了检测数字水印是否被修改或删除，可以使用数字水印算法。一种常见的数字水印算法是LSB（Least Significant Bit）算法，即将数字水印嵌入到图片的最低有效位中。具体步骤如下：

1.将数字水印转换为二进制序列

watermark = '123'
watermark_binary = ''.join(format(ord(c), '08b') for c in watermark)

2.打开图片

im = Image.open('watermark.jpg')

3.将图片转换为像素矩阵

pixels = im.load()
width, height = im.size

4.将数字水印嵌入到最低有效位中

index = 0
for y in range(height):
    for x in range(width):
        r, g, b = pixels[x, y]
        if index < len(watermark_binary):
            r_binary = format(r, '08b')
            r_binary = r_binary[:-1] + watermark_binary[index]
            r = int(r_binary, 2)
            pixels[x, y] = (r, g, b)
            index += 1
        else:
            break
    else:
        continue
    break

5.保存图片

im.save('watermark_modified.jpg')

6.检测数字水印是否被修改或删除

im_modified = Image.open('watermark_modified.jpg')
pixels_modified = im_modified.load()
width_modified, height_modified = im_modified.size
index = 0
watermark_binary_modified = ''
for y in range(height_modified):
    for x in range(width_modified):
        r_modified, g_modified, b_modified = pixels_modified[x, y]
        r_binary_modified = format(r_modified, '08b')
        watermark_binary_modified += r_binary_modified[-1]
        index += 1
        if index == len(watermark_binary):
            break
    else:
        continue
    break
watermark_modified = ''.join(chr(int(watermark_binary_modified[i:i+8], 2)) for i in range(0, len(watermark_binary_modified), 8))
if watermark == watermark_modified:
    print('数字水印未被修改或删除')
else:
    print('数字水印已被修改或删除')