title: resizing all images in a folder using PIL
body: <p>i'm able to resize each image one at a time,but how can I resize all images in one folder in a similar way? Please help me.</p>
  
  <pre><code>from PIL import Image
  from resizeimage import resizeimage
      with open('test-image.jpeg', 'r+b') as f:
          with Image.open(f) as image:
              cover = resizeimage.resize_cover(image, [200, 100])
              cover.save('test-image-cover.jpeg', image.format)
  </code></pre>