验证码报错

[BeyondHeaven]

crd@crd-PC:~/Desktop/ccgp_crack/PythonSpiderNotes/Captcha1$ python tess_test.py
PNG (200, 70) 1
Traceback (most recent call last):
File "tess_test.py", line 224, in
filter_enhance(midu_image_name, midu_image_name_pro1)
File "tess_test.py", line 91, in filter_enhance
im = enhancer.enhance(2)
File "/usr/local/lib/python2.7/dist-packages/PIL/ImageEnhance.py", line 37, in enhance
return Image.blend(self.degenerate, self.image, factor)
File "/usr/local/lib/python2.7/dist-packages/PIL/Image.py", line 2631, in blend
return im1._new(core.blend(im1.im, im2.im, alpha))
ValueError: image has wrong mode

请问这是怎么回事？谢谢