First, we need a convert utility to resize the jpg images.

convert utility is from ImageMagick (open source tool)

If you dont have the convert utility, then install it by using the below command.

1

sudo apt-get install imagemagick

After installation, we are ready to resize the images.

execute the below command to resize the image to 50% from its original size

1
2

syntax:
convert source-image -resize 50% output-image

1

convert linux.jpg -resize 50% resize_linux.jpg

If you want to resize all the pictures in one folder, then try with this for loop

1

for i in *.jpg; do new_file=${i/.*/};convert ${i} -resize 50% ${i} ${new_file}_new.jpg; done

This convert utility converts the image from one format to another format ( Eg. jpg to png )

1

convert linux.jpg linux.png