Sometimes, you need to fill an application form, but the size of your image is
too large, as per the mentioned size on the application. So, you can use imagemagick
utility of ubuntu, and get the desired size for your image.
To reduce the image size, you can run either of the below command.
$ convert -resize 50% source.png dest.jpg and $ convert -resize 1024X768 source.png dest.jpg