python使用PIL模块实现给图片打水印的方法

本文实例讲述了python使用PIL模块实现给图片打水印的方法。分享给大家供大家参考。具体实现方法如下：

    import Image, ImageEnhance
    def reduce_opacity(im, opacity):
      """Returns an image with reduced opacity."""
      assert opacity >= 0 and opacity <= 1
      if im.mode != 'RGBA':
        im = im.convert('RGBA')
      else:
        im = im.copy()
      alpha = im.split()[3]
      alpha = ImageEnhance.Brightness(alpha).enhance(opacity)
      im.putalpha(alpha)
      return im
    def watermark(im, mark, position, opacity=1):
      """Adds a watermark to an image."""
      if opacity < 1:
        mark = reduce_opacity(mark, opacity)
      if im.mode != 'RGBA':
        im = im.convert('RGBA')
      # create a transparent layer the size of the image and draw the
      # watermark in that layer.
      layer = Image.new('RGBA', im.size, (0,0,0,0))
      if position == 'tile':
        for y in range(0, im.size[1], mark.size[1]):
          for x in range(0, im.size[0], mark.size[0]):
            layer.paste(mark, (x, y))
      elif position == 'scale':
        # scale, but preserve the aspect ratio
        ratio = min(
          float(im.size[0]) / mark.size[0], float(im.size[1]) / mark.size[1])
        w = int(mark.size[0] * ratio)
        h = int(mark.size[1] * ratio)
        mark = mark.resize((w, h))
        layer.paste(mark, ((im.size[0] - w) / 2, (im.size[1] - h) / 2))
      else:
        layer.paste(mark, position)
      # composite the watermark with the layer
      return Image.composite(layer, im, layer)
    def test():
      im = Image.open('test.png')
      mark = Image.open('overlay.png')
      watermark(im, mark, 'tile', 0.5).show()
      watermark(im, mark, 'scale', 1.0).show()
      watermark(im, mark, (100, 100), 0.5).show()
    if __name__ == '__main__':
      test()

希望本文所述对大家的Python程序设计有所帮助。