保存图片到buffer

image_to_string.py

### 保存图片到内存
import StringIO
output = StringIO.StringIO()
format = 'PNG' # or 'JPEG' or whatever you want
image.save(output, format)
contents = output.getvalue()
output.close()


### 保存图片到文件
file = 'image.png'
image.save(file_name)
with open(file_name) as f:
    image = StringIO.StringIO(f.read())
    upload_image(image, file_name)