Converting hundreds of jpg to PDF using Terminal

Question

I know that the command convert *.jpg myPdf1.pdf can convert multiple JPEG files into a single PDF.

But I would like to convert multiple JPEGs into multiple PDFs, for example:

myJPG1.jpg → myPDF1.pdf
myJPG2.jpg → myPDF2.pdf
myJPG3.jpg → myPDF3.pdf

Is there any decent way to manage something like that?

Solution 1

My first instinct for batch processing files is almost always find. It's excellent if you need to build in any sort of filtering (which you don't here) but it's still a favourite. This will also recurse into subdirectories unless you tell it (with -maxdepth 1 or other):

find -name '*.jpg' -exec convert "{}" "{}.pdf" \;
rename 's/\.jpg\.pdf$/.pdf/' *.jpg.pdf

The find/convert statement will output a load of .jpg.pdf files. The second cleans this up.

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Perhaps a slightly more elegant approach in such a simple case:

for file in *.jpg ; do convert "$file" "${file/%jpg/pdf}"; done

This doesn't recurse and you don't have to mess around cleaning up the filenames.

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And I almost forgot, ImageMagick has a numerical output which might fit your use-case perfectly. The following will just stick a three-digit identifier (000, 001, 002, etc) on the end of the "myPDF":

convert *.jpg myPDF%03d.pdf

Obviously if you're dealing with more than a thousand entries, increase the number. If you don't want it zero-padded, remove the leading zero.

Solution 2

Unfortunately, convert changes the image quality before "packing it" into the PDF. So, to have minimal loss of quality, is better to put the original jpg, (works with .png too) into the PDF, you need to use img2pdf.

I use these commands:

With time I discovered a simpler, shorter one liner solution also using img2pdf that doesn't need pdftk as in the original answer

1. Make PDF

   img2pdf *.jp* --output combined.pdf

2. (optional) OCR the output PDF

   ocrmypdf combined.pdf combined_ocr.pdf

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Below is the original answer commands with more command and more tools needed:

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1. This to make a pdf file out of every jpg image without loss of either resolution or quality:

   ls -1 ./*jpg | xargs -L1 -I {} img2pdf {} -o {}.pdf

2. Here you will have the *.pdfs as *.jpg.pdf, so will do a little renaming

   mmv "*.jpg.pdf" "#1.pdf"

You need to have installed img2pdf and mmv

sudo apt install img2pdf mmv

Comments

[jobin]

How would you order them?

[Physics_maths]

Well suppose they are called myJPG1, myJPG2 and so on, and you want to convert them to myPDF1, myPDF2 and so on.

[jobin]

The question isn't clear, do you have multiple jpgs or pdfs? You can convert multiple jpgs to a single pdf using the command you have used in your question.

[Physics_maths]

It should be clearer now, I just want a bunch of PDF's with names myPDF1 myPDF2 and so on. But Your suggestion, into a single PDF, also sounds nice. Thanks.

[Yauhen Yakimovich]

find -name '*.jpg' | parallel 'convert {} {.}.pdf'