Questions[jpeg](ubuntu)

I've got a bunch of photos that were on an SD card. Most of them are corrupted now and I cannot open them in any program (Gwenview, GIMP, same on Windows...). But every file browser can still correctly show most of their thumbnails. For instance, here is Gwenview with a photo selected that have a correct thumbnail:

I'm aware that the SD card is probably dying, so I already made an image of the SD card, with dd, on which I can work.

So far, my searches led me to PhotoRec, which does not work in my case: it recovered four useless photos and about two thirds of my ~400 images still have their thumbnail. I still hope to get most of those back.

What can I do? Any help is appreciated :)

PS: I'm on Kubuntu 20.04, I'm able to be root and I'm not afraid of the command line (but a graphical tool is still handy :D).

I have multiple *.jpeg pictures I like to merge into a single *.pdf file like so:

convert Blatt1.jpg Blatt2.jpg Blatt3.jpg Blatt4.jpg out.pdf

I am prompted with the following exception:

convert: attempt to perform an operation not allowed by the security policy `PDF' @ error/constitute.c/IsCoderAuthorized/408

What causes this problem and how can I fix it? I did some research but couldn't find anything about this particular problem.

I am using GIMP v.2.8.16 to combine several figures from different file formats into a single JPEG image. I'm able to accomplish this and save as JPEG, and open it on my computer perfectly fine, but when I go to upload it to a website which requires .jpg format files the file is not recognized as a jpeg. I've had this issue multiple times now where the .jpg exported by GIMP is not recognized by other programs.

Just to test that it was related to GIMP, I combined the same figures using LibreOffice Impress and saved as a JPEG, and this file was able to be uploaded with no problems.

Has anyone else experienced this issue and/or come up with a solution?

I'm trying to convert a PDF file (it's a book) into an image.

When I using convert like this

convert book.pdf book.jpg

or like this

convert book.pdf book.png

then I get this warning

Warning: Short look-up table in the Indexed color space was padded with 0's

for each page.

Is there some other tool I can use for conversion to get a bunch of images for this, or can someone show me a different way to solve this problem?

Recently, I extracted some pictures from an .iso file, but I can't see them. When I try to open these .jpg files with Image Viewer, it shows me this error:

Error interpreting JPEG image file (Not a JPEG file: starts with 0xda)

(the expression after 0x is different from file to file)

I tried changing the file extension but no result.
Thanks for help!