Bulk converting images from one format to another?

Try these commands,

mogrify -format png /path/*.jpg    

This will convert all the .jpg files into .png files and saves the converted files in the same directory.

mv /path/*.png ~/Desktop/pic

This will moves all the .png files(converted) to the pic directory which resides on the Desktop.

Disclaimer:

If you want to keep the orientation of your image you have to add -auto-orient to the command. You can find out why here. The mogrify command which keeps the orientation would look like this:

mogrify -auto-orient -format png /path/*.jpg    

Using ImageMagick.

First install imagemagick:

sudo apt-get install imagemagick

Try converting just one image at first:

convert image.jpg image.png

Now convert all:

mogrify -format png *.jpg

EDIT

You also need to split it into chunks that will fit to avoid hitting the limit of how much you can put on a command line. This should work better:

find -name '*.jpg' -print0 | xargs -0 -r mogrify -format png

The -print0 and -0 are used to handle spaces in filenames and the -r means don't run mogrify if there's nothing to do.

Source: https://stackoverflow.com/questions/1010261/running-a-batch-with-imagemagick

EDIT 2 Switched png and jpg as per @Glutanimate's comment.

EDIT 3 Changed png to jpg in last suggestion.

Firstly, convert works. You don't need to test it. Secondly, a bash oneliner suits the need:

$ for file in Ground*jpg; do { \
  echo "Converting $file to `echo $file|cut -d. -f1`.png" ;\
  convert $file `echo $file|cut -d. -f1`.png ; } done

Rockin' it auldskewl ;)

Cheers

I know it's been a long time since this question was put but there is one brilliant piece of software that has not been mentioned that I have used a lot.

http://photobatch.wikidot.com/ also known as Phatch. It literally converts anything from anything to anything else in image terms. It had not been updated for a while but now claims to be released for ubuntu 17.10. Give it a try. I'm confident you'll be very happy with it.