How to convert a PDF into JPG with command line in Linux?

For the life of me, over the last 5 years, I cannot get imagemagick to work consistently (if at all) for me, and I don't know why people continually recommend it again and again. I just googled how to convert a PDF to a JPEG today, found this answer, and tried convert, and it doesn't work at all for me:

Broken command (doesn't work for me):

# BROKEN cmd
$ convert in.pdf out.jpg
convert-im6.q16: not authorized `in.pdf' @ error/constitute.c/ReadImage/412.
convert-im6.q16: no images defined `out.jpg' @ error/convert.c/ConvertImageCommand/3258.

(Update 24 Feb. 2022: here is the fix for imagemagick so convert will work. See also my comment here, and my comments under this answer here. I still like pdftoppm, below, much better, however.)

Then, I remembered there was another tool I use and wrote about, so I googled "linux convert pdf to jpg Gabriel Staples", clicked the first hit, and scrolled down to my answer. Here's what works perfectly for me. This is the basic command format:

Good command--use this instead:

# GOOD cmd
pdftoppm -jpeg -r 300 input.pdf output 

The -jpeg sets the output image format to JPG, -r 300 sets the output image resolution to 300 DPI, and the word output will be the prefix to all pages of images, which will be numbered and placed into your current directory you are working in. A better way, in my opinion, however, is to use mkdir -p images first to create an "images" directory, then set the output to images/pg so that all output images will be placed cleanly into the images dir you just created, with the file prefix pg in front of each of their numbers.

Therefore, here are my favorite commands:

1. [Produces ~1MB-sized files per pg] Output in .jpg format at 300 DPI:

    mkdir -p images && pdftoppm -jpeg -r 300 mypdf.pdf images/pg
   

2. [Produces ~2MB-sized files per pg] Output in .jpg format at highest quality (least compression) and still at 300 DPI:

    mkdir -p images && pdftoppm -jpeg -jpegopt quality=100 -r 300 mypdf.pdf images/pg
   

3. If you need more resolution, you can try 600 DPI:

    mkdir -p images && pdftoppm -jpeg -r 600 mypdf.pdf images/pg
   

4. ...or 1200 DPI:

    mkdir -p images && pdftoppm -jpeg -r 1200 mypdf.pdf images/pg
   

See the references below for more details and options.

References:

1. [my answer] Convert PDF to image with high resolution
2. [my answer] https://askubuntu.com/questions/150100/extracting-embedded-images-from-a-pdf/1187844#1187844

_{Keywords: ubuntu linux convert pdf to images; pdf to jpeg; ptdf to tiff; pdf2images; pdf2tiff; pdftoppm; pdftoimages; pdftotiff; pdftopng; pdf2png}

You can try ImageMagick's convert utility.

On Ubuntu, you can install it with this command:

$ sudo apt-get install imagemagick

Use convert like this:

$ convert input.pdf output.jpg
# For good quality use these parameters
$ convert -density 300 -quality 100 in.pdf out.jpg