Command Line Bulk converting images from one format to another

First install imagemagick:

sudo apt-get install imagemagick

1. Try converting just one image at first: to ensure that it works

convert image.jpg image.png

2. Now convert all:(jpg to png)

mogrify -format png *.jpg

3. Resize

mogrify -resize 50% sharpfinal.png

4. Save as a jpg and output to the directory ‘new_folder’:

mogrify    -format jpg -path ./new_folder  *.png

5. Save as a jpg, output to ‘new_folder’, resize to 50%:

mogrify    -format jpg -resize 50% -path ./new_folder  *.png