Demonstrates logic bug in scaling function

gistfile1.py

# Test for scaling function. Python 2.7.
# http://www.nerdydork.com/django-custom-upload-handler-to-compress-image-files.html
def scale_dimensions(width, height, longest_side):
    if width > longest_side:
        ratio = longest_side * 1. / width
        return (int(width * ratio), int(height * ratio))
    elif height > longest_side:
        ratio = longest_side * 1. / height
        return (int(width * ratio), int(height * ratio))
    return (width, height)


def scale_dimensions2(width, height, longest_side):
    if width <= longest_side and height <= longest_side:
        return width, height
        
    # Force a float to avoid integer division rounding.
    ratio = float(width) / height
    
    # Landscape
    if ratio > 1:
        return longest_side, longest_side / ratio
    # Portrait
    else:
        return longest_side * ratio, longest_side


tests = [
    # Width, height, longest side
    (800, 600, 500),
    (600, 800, 500), # scale_dimensions gives 500 x 666!
    (800, 600, 700),
    (600, 800, 700),
    (100, 100, 200),
    
]


for idx, (w, h, m) in enumerate(tests):
    w2, h2 = scale_dimensions(w, h, m)
    w3, h3 =  scale_dimensions2(w, h, m)

    print "{idx}: {} x {}, fit to {}".format(w, h, m, idx=idx)
    print "    {idx}a: {} x {}       {idx}b: {} x {}".format(w2, h2, w3, h3, idx=idx)