Cannot use 'keep'. jpg not recognized as jpg

[soundreactor]

i was trying to resize images and keep the quality setting.
with quality set to a digit it works fine.
probably similar to issue:
#857

i suspect i have some sort of jpg type that is also not recognized as jpg, just like in the issue.
so i added it inside a zip.

What are your OS, Python and Pillow versions?

• OS: windows
• Python: 3.7.3
• Pillow: 6.1.0

IMG_7679.zip

from PIL import Image
import os, sys

Image.MAX_IMAGE_PIXELS = None

path = "C:/Users/KE/Desktop/omas 80 Panting Images/"
dirs = os.listdir( path )

def resize():
    for item in dirs:
        if os.path.isfile(path+item) and item.endswith('.jpg'):
            print(path+item)
            # break
            im = Image.open(path+item)
            size = im.size


            f, e = os.path.splitext(path+item)

            if(size[0]>size[1]):
                imResize = im.resize((5000,int(5000*size[1]/size[0])), Image.ANTIALIAS)

            if(size[0]<size[1]):
                imResize = im.resize((int(5000*size[0]/size[1]),5000), Image.ANTIALIAS)


            f = f.replace(path, path + "max/")
            imResize.save(f + '.jpg', 'JPEG', quality='keep')
            # imResize.save(f + '.jpg', 'JPEG', quality=20)

resize()

[hugovk]

Thank you for the report.

That's quite a bit of code, please could you reduce it to the smallest self-contained, runnable amount that still reproduces the problem? Tips here:

• https://stackoverflow.com/help/mcve

[soundreactor]

so i think i found the problem.

this is what happens.

im = Image.open(path)
print(im.format)

JPEG

imResize = im.resize((500,500), Image.ANTIALIAS)
print(imResize.format)

None

somehow after im.resize the image is not a jpeg anymore.
i guess its not intended for that use case.
i'm now using. im.thumbnail((500,500)) which works fine. its still a jpeg and so it can keep the quality.

the only question is: if the None format is intended behavior or not?

test code

from PIL import Image

Image.MAX_IMAGE_PIXELS = None

path = "C:/Users/KE/Desktop/omas 80 Panting Images/IMG_7679.jpg"

im = Image.open(path)
print(im.format)

## this won't work
# imResize = im.resize((500,500), Image.ANTIALIAS)

##this will work
im.thumbnail((500,500))
imResize = im

print(imResize.format)

nupath = path.replace("IMG_7679", "IMG_7679_resized")
imResize.save(nupath, 'JPEG', quality='keep')

[radarhere]

Yes. So im.thumbnail is modifying the image in-place, while im.resize is creating a copy of the image. The copy is no longer a JPEG - it doesn't take with it all of the information from im. This is how the Pillow copy operation behaves in general, it's not specific to your situation.

[radarhere]

https://pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.format

PIL.Image.format
The file format of the source file. For images created by the library itself (via a factory function, or by running a method on an existing image), this attribute is set to None.

[soundreactor]

okey. makes sense.
i think i was confused by the error message and that's why i didn't look at the right place.
"Cannot use 'keep' when original image is not a JPEG"
i directly thought of the original input image. now its clear to me that that is of course silly, how would save know what the original input image was in the first place. it just cares if it gets a type JPEG or not.

[radarhere]

Cool. Enjoy continuing to use Pillow. Let us know if you have any further questions