Jpg thumbnail showing larger than the original picture

Question

I recently downloaded a picture from LinkedIn, and something really weird happens with it. Let me just state before that I can't show you the author asked me don't show it.

So, if I do "read informations" of the picture, it is 139 x 139 pixels. I can open it everywhere, it will have this square shape and this 139 x 139 size. But, when I look at it on my computer desktop, it appears way larger, and not even squared. It is in horizontal rectangle shape, and if I enlarge the thumbnail size, it shows way more than what I can see in Preview, photoshop, and every applications that can read pictures (it is not an impression, it really shows outside the square).

So I opened it in an exif reader, and in it, it says the size is actually 2048 x 1536, and the preview of the image is now as the thumbnail . I also tried to open it in chrome, and send it to an exif viewer extension, and the extension crashed every time I tried.

I searched for this type of problem, and I found nothing. Some people told me to use an hexadecimal reader, but I have no idea of how it works.

I need help try to get this picture in the size showed in the thumbnail . Thanks for your help :)

Answer 1

What can have happened is the original picture had a large thumbnail (the thumbnail is actually a JPEG-in-the-JPEG in the metadata) and that it was scaled down but with the metadata left in(*) , so now the thumbnail is bigger than the original. You can extract metadata with some EXIF-handling utilities, for instance with exiftool

exiftool -b -PreviewImage -w _preview.jpg <your image>

or

exiftool -b -preview:all -w _preview.jpg <your image>

Note that the preview is of moderate quality (on my DSLR, the preview are full-size, quality 80).

(*) this also happens if the photo was shot in "raw" form, and the metadata left in by demosaicing apps. This is even more likely if the image thumbnail is full-size (thumbnails in JPEGs are usually smaller images than the original)