Has anyone else noticed that, since February or March, JPEG files downloaded from Jow Forums are different from the original? They are a byte or two heavier and their md5 checksum does not match. Does anybody know why this is happening?
Source of this image: upload.wikimedia.org
Botnet so they can know an image was downloaded from Jow Forums.
That's weird, the images are the same in all other respects except when it was downloaded from here?
Jow Forums has always stripped exif data, at least, so it's not unknown that it is modifying image uploads.
>always
It hasn't been that long actually
since we're on the topic
one thing that really pissed me off about Jow Forums is their removal of ALL EXIF data. I understand they had to combat doxxing somehow, but all they had to do was remove the GPS fields
then there's smartphones, automatically resizing, resampling, cropping, adjusting colors or brightness, and all that other shit. so one image may have like 25 different versions on the internet. before this keeping track of duplicate wasn't even something you worried about. search and match file size and usually you had your duplicates. now you need all kinds of photo recognition to analyze the elements in the pic and compare them with each other. very CPU intensive and wasteful of time.
Removing exif data shouldn't make the file larger though, should it?
I forgot EXIF is useful to ascertain the image integrity. if you see widely mismatched saved and modified dates you know the image's been tampered.
if they resaved the image using different settings it can. the way to make sure image data is identical is save the two pics as bmp (using the same software) then do byte-by-byte comparison.
EXIF stripping aside, 4chin uses an autistic huffman table optimized for english letters lol.
I know that feel. I've started to save only GIFs and PNGs and convert small JPGs into those.
Since 2012 at least. I don't recall when it started, but you're right, it wasn't from literally the beginning because the site was barely anything in 2003-2005.
Really? The quantization is different than JPEG other JPEG implementations?
Someone check to see if it's modifying the content of the image. It's simple. Just use imagemagick and iterate over each pixel and save a new image from the pixel data. Do this for the original and the version you download from Jow Forums. Compare checksums for the output images.
>iterate over the pixels
Please stop trying to sound like you know what you are talking about.
>being this retarded
Using ImageMagick, you can iterate over the pixel data in the form of a 2 dimensional array.
Or you can just render each jpeg, save the bitmaps, and compare.
That's not possible. Prove me wrong.
convert before.jpg before.bmp
convert after.jpg after.bmp
cmp before.bmp after.bmp
pics or it didn't happen
Couldn't you just compare the signatures?
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t-thanks Jow Forums