watermark.py

from PIL import Image



class WatermarkApp:
    def __init__(self):
        pass
    
    def process_image(self, image):
        watermark = Image.open('asset/chaojihui-v2.png')
        # 获取水印的等比例缩放尺寸
        wm_width, wm_height = watermark.size
        target_size = 400
        alpha = 0.3

        if wm_width > wm_height:
            new_wm_width = target_size
            new_wm_height = int((wm_height / wm_width) * target_size)
        else:
            new_wm_height = target_size
            new_wm_width = int((wm_width / wm_height) * target_size)

        wm = watermark.resize((new_wm_width, new_wm_height), Image.Resampling.LANCZOS)

        # 处理透明度
        if alpha < 1.0:
            wm = self.apply_transparency(wm, alpha)

        # 确保原图是RGBA模式
        if image.mode != 'RGBA':
            image = image.convert('RGBA')

        # 在整个图片上铺满水印
        for y in range(0, image.height, new_wm_height):
            for x in range(0, image.width, new_wm_width):
                image.alpha_composite(wm, dest=(x, y))
        return image

    def apply_transparency(self, watermark, alpha):
        """应用透明度"""
        matrix = watermark.split()[-1].point(lambda x: x * alpha)
        watermark.putalpha(matrix)
        return watermark