rotate photos based on exif orientation

from PIL import Image
import piexif

def rotate_img(img, rotate_param):
    e = piexif.load(img.info["exif"])
    e['0th'][274] = 1 # no rotate
    if rotate_param in [Image.ROTATE_90, Image.ROTATE_270]:
        e['Exif'][40962], e['Exif'][40963] \
            = e['Exif'][40963], e['Exif'][40962] # swap width, height

    img = img.transpose(rotate_param)
    output = BytesIO()
    img.save(output, 'JPEG', quality=90, exif=piexif.dump(e))
    length = output.tell()
    output.seek(0)
    return img, output, length

img = Image.open('file')
e = piexif.load(img.info["exif"])
if self.exif and 'Orientation' in self.exif:
    if self.exif['Orientation'] == 3:
        img, output, length = rotate_img(self, img, Image.ROTATE_180)
    elif self.exif['Orientation'] == 6:
        img, output, length = rotate_img(self, img, Image.ROTATE_270)
    elif self.exif['Orientation'] == 8:
        img, output, length = rotate_img(self, img, Image.ROTATE_90)