Thumbnail function thats force images to be given size

import glob
from PIL import Image

class SmartThumbnail:
    # file (string) , target (string), maxSizes (tuple)
    def __init__(self, file, target, maxSizes):
        self.file     = file
        self.target   = target
        self.maxSizes = maxSizes

    def createThumb(self):
      self.im = Image.open(self.file)
      
      # birtakim hesaplamalar
      orig_width, orig_height   = self.im.size
      if orig_width  > maxSizes[0] and orig_height > maxSizes[1]:
        thumb_width, thumb_height = self.maxSizes
        orig_ratio, thumb_ratio   = float(orig_width) / float(orig_height), float(thumb_width) / float(thumb_height)
        
        if thumb_ratio < orig_ratio:
            crop_height = orig_height
            crop_width  = crop_height * thumb_ratio
            x_offset = float(orig_width - crop_width) / 2
            y_offset = 0
        else:
            crop_width = orig_width
            crop_height = crop_width / thumb_ratio
            x_offset = 0
            y_offset = float(orig_height - crop_height) / 3
        
        # crop it
        self.im = self.im.crop((x_offset, y_offset, x_offset+int(crop_width), y_offset+int(crop_height)))
        self.im = self.im.resize((thumb_width, thumb_height), Image.ANTIALIAS)
        self.im.save(self.target)
        
        return self.im
      else:
        pass

images =  glob.glob("*.jpg")
for image in images:
    th = SmartThumbnail(image, image, (800, 600))
    th.createThumb()