PIL thumbnail is rotating my image?

I'm attempting to take large (huge) images (from a digital camera), and convert them into something that I can display on the web. This seems straightforward, and probably should be. However, when I attempt to use PIL to create thumbnail versions, if my source image is taller than it is wide, the resulting image is rotated 90 degrees, such that the top of the source image is on the left of the resulting image. If the source image is wider than it is tall, the resulting image is the correct (original) orientation. Could it have to do with the 2-tuple I send in as the size? I'm using thumbnail, because it appears it was meant to preserve the aspect ratio. Or am I just being completely blind, and doing something dumb? The size tuple is 1000,1000 because I want the longest side to be shrunk to 1000 pixels, while keeping AR preserved.

Code seems simple

img = Image.open(filename)
img.thumbnail((1000,1000), Image.ANTIALIAS)
img.save(output_fname, "JPEG")

Thanks in advance for any help.

Solution 1:

I agree with almost everything as answered by "unutbu" and Ignacio Vazquez-Abrams, however...

EXIF Orientation flag can have a value between 1 and 8 depending on how the camera was held.

Portrait photo can be taken with top of the camera on the left, or right edge, landscape photo could be taken upside down.

Here is code that takes this into account (Tested with DSLR Nikon D80)

    import Image, ExifTags

    try :
        image=Image.open(os.path.join(path, fileName))
        for orientation in ExifTags.TAGS.keys() : 
            if ExifTags.TAGS[orientation]=='Orientation' : break 
        exif=dict(image._getexif().items())

        if   exif[orientation] == 3 : 
            image=image.rotate(180, expand=True)
        elif exif[orientation] == 6 : 
            image=image.rotate(270, expand=True)
        elif exif[orientation] == 8 : 
            image=image.rotate(90, expand=True)

        image.thumbnail((THUMB_WIDTH , THUMB_HIGHT), Image.ANTIALIAS)
        image.save(os.path.join(path,fileName))

    except:
        traceback.print_exc()

Solution 2:

Just use PIL.ImageOps.exif_transpose from Pillow.

Unlike every single function proposed in answers to this question, including my original one, it takes care to remove the orientation field from EXIF (as the image is no longer oriented in a strange way) and also to ensure the return value is a brand new Image object so changes to it can’t affect the original one.

Solution 3:

xilvar's answer is very nice, but had two minor shortcomings that I wanted to fix in a rejected edit, so I'll post it as an answer.

For one, xilvar's solution fails if the file isn't a JPEG or if there is no exif data present. And for the other, it always rotated 180 degrees instead of the appropriate amount.

import Image, ExifTags

try:
    image=Image.open(os.path.join(path, fileName))
    if hasattr(image, '_getexif'): # only present in JPEGs
        for orientation in ExifTags.TAGS.keys(): 
            if ExifTags.TAGS[orientation]=='Orientation':
                break 
        e = image._getexif()       # returns None if no EXIF data
        if e is not None:
            exif=dict(e.items())
            orientation = exif[orientation] 

            if orientation == 3:   image = image.transpose(Image.ROTATE_180)
            elif orientation == 6: image = image.transpose(Image.ROTATE_270)
            elif orientation == 8: image = image.transpose(Image.ROTATE_90)

    image.thumbnail((THUMB_WIDTH , THUMB_HIGHT), Image.ANTIALIAS)
    image.save(os.path.join(path,fileName))

except:
    traceback.print_exc()

Solution 4:

Please note that there are better answers below.

When a picture is taller than it is wide, it means the camera was rotated. Some cameras can detect this and write that info in the picture's EXIF metadata. Some viewers take note of this metadata and display the image appropriately.

PIL can read the picture's metadata, but it does not write/copy metadata when you save an Image. Consequently, your smart image viewer will not rotate the image as it did before.

Following up on @Ignacio Vazquez-Abrams's comment, you can read the metadata using PIL this way, and rotate if necessary:

import ExifTags
import Image

img = Image.open(filename)
print(img._getexif().items())
exif=dict((ExifTags.TAGS[k], v) for k, v in img._getexif().items() if k in ExifTags.TAGS)
if not exif['Orientation']:
    img=img.rotate(90, expand=True)
img.thumbnail((1000,1000), Image.ANTIALIAS)
img.save(output_fname, "JPEG")

But be aware that the above code may not work for all cameras.

The easiest solution maybe to use some other program to make thumbnails.

phatch is a batch photo editor written in Python which can handle/preserve EXIF metadata. You could either use this program to make your thumbnails, or look at its source code to see how to do this in Python. I believe it uses the pyexiv2 to handle the EXIF metadata. pyexiv2 may be able to handle EXIF better than the PIL's ExifTags module.

imagemagick is another possibility for making batch thumbnails.

Solution 5:

Here's a version that works for all 8 orientations:

def flip_horizontal(im): return im.transpose(Image.FLIP_LEFT_RIGHT)
def flip_vertical(im): return im.transpose(Image.FLIP_TOP_BOTTOM)
def rotate_180(im): return im.transpose(Image.ROTATE_180)
def rotate_90(im): return im.transpose(Image.ROTATE_90)
def rotate_270(im): return im.transpose(Image.ROTATE_270)
def transpose(im): return rotate_90(flip_horizontal(im))
def transverse(im): return rotate_90(flip_vertical(im))
orientation_funcs = [None,
                 lambda x: x,
                 flip_horizontal,
                 rotate_180,
                 flip_vertical,
                 transpose,
                 rotate_270,
                 transverse,
                 rotate_90
                ]
def apply_orientation(im):
    """
    Extract the oritentation EXIF tag from the image, which should be a PIL Image instance,
    and if there is an orientation tag that would rotate the image, apply that rotation to
    the Image instance given to do an in-place rotation.

    :param Image im: Image instance to inspect
    :return: A possibly transposed image instance
    """

    try:
        kOrientationEXIFTag = 0x0112
        if hasattr(im, '_getexif'): # only present in JPEGs
            e = im._getexif()       # returns None if no EXIF data
            if e is not None:
                #log.info('EXIF data found: %r', e)
                orientation = e[kOrientationEXIFTag]
                f = orientation_funcs[orientation]
                return f(im)
    except:
        # We'd be here with an invalid orientation value or some random error?
        pass # log.exception("Error applying EXIF Orientation tag")
    return im