TIFF orientation tag handled differently from most other software when loading G4 TIFF files

[ailintom]

Most image software handles TIFF orientation tags (tag 274) differently from Pillow when loading binary G4 TIFF images. This means that only images having the orientation tag == 1 (The 0th row represents the visual top of the image, and the 0th column represents the visual left-hand side) are loaded correctly (in the same way as in other software), other images should be corrected manually.
I am not sure whether Pillow regards the orientation tags while other software ignores or vice versa. At least they are loaded transposed.
I use Pillow-6.1.0 with Python 3.8 on Windows.

I've developed the following procedure in my script to load TIFF files correctly (basically I only have files with orientation==8 from my office copier machine, so I have not tested other orientations). I think this something similar should be part of the TIFFImagePlugin

from PIL import Image
from tkinter import filedialog, Tk
ORIENTATION = 274
root = Tk()
root.withdraw()
file_selected = filedialog.askopenfilename()
srcim = Image.open(filename)
orientation = srcim.tag[ORIENTATION][0]
format = os.path.splitext(filename)[1]
if format.lower() in [".tif", ".tiff"]:
     try:
        if orientation == 8:
            srcim = srcim.transpose(Image.ROTATE_90)
        elif orientation == 3:
            srcim = srcim.transpose(Image.ROTATE_180)
        elif orientation == 6:
            srcim = srcim.transpose(Image.ROTATE_270)
        elif orientation == 2:
            srcim = srcim.transpose(Image.FLIP_LEFT_RIGHT)
        elif orientation == 4:
            srcim = srcim.transpose(Image.FLIP_TOP_BOTTOM)
        elif orientation == 5:
            srcim = srcim.transpose(Image.ROTATE_90).transpose(Image.FLIP_LEFT_RIGHT)
        elif orientation == 7:
            srcim = srcim.transpose(Image.ROTATE_270).transpose(Image.FLIP_LEFT_RIGHT)
     except:
          print("Can't detect orientation")

[radarhere]

Hi. In Pillow 6.0, ImageOps.exif_tranpose was added -

Pillow/src/PIL/ImageOps.py

Lines 523 to 530 in 1e3c2c9

	def exif_transpose(image):
	"""
	If an image has an EXIF Orientation tag, return a new image that is
	transposed accordingly. Otherwise, return a copy of the image.
	:param image: The image to transpose.
	:return: An image.
	"""

So you should be able to simplify your code down to -

from PIL import Image, ImageOps
from tkinter import filedialog, Tk
root = Tk()
root.withdraw()
file_selected = filedialog.askopenfilename()
srcim = Image.open(filename)
srcim = ImageOps.exif_transpose(src_im)

If you're asking why this is not applied automatically, the answer would be that ImageOps.exif_transpose has not always been a part of Pillow, and we value backwards compatibility highly.

[ailintom]

Hi, thanks for the reply. No, exif_transpose does not help. I mean TIFF tags, not the EXIF, it is a different thing. Try loading this file with PIL
It shows upright in most graphic software, but PIL displays it rotated, because it disregards the TIFF 274 tag (orientation)
test1.zip

[ailintom]

Here is the updated procedure for correcting TIFF file orientation:

from PIL import Image
TIFFTAG_ORIENTATION = 274
def correct_tiff(srcim):
    try:
        orientation = srcim.tag[TIFFTAG_ORIENTATION][0]
        

        if orientation == 2:
            srcim = srcim.transpose(Image.FLIP_LEFT_RIGHT)
        elif orientation == 3:
            srcim = srcim.transpose(Image.ROTATE_180)            
        elif orientation == 4:
            srcim = srcim.transpose(Image.FLIP_TOP_BOTTOM)
        elif orientation == 5:
            srcim = srcim.transpose(Image.TRANSPOSE)
        elif orientation == 6:
            srcim = srcim.transpose(Image.ROTATE_270)            
        elif orientation == 7:
            srcim = srcim.transpose(Image.TRANSVERSE)
        elif orientation == 8:
            srcim = srcim.transpose(Image.ROTATE_90)       
    except:
        pass
    return srcim

and a small test script with a full set of test files (tiff G4 and uncompressed)
attached.

tiff orientation test.zip

[radarhere]

Thanks for all that. Could any of those images be be added to the test suite, under the Pillow license?

[ailintom]

Yes, both code snippets and the images are absolutely free to use under any license.

[radarhere]

Okay. I've created #4062 to add an ImageOps.auto_transpose method. See what you think.

[radarhere]

I've now created #4063 to transpose TIFF images on load instead.