If you like to add some vintage like retro game feeling to your website, try use pixel art images might be a good idea. Here’s a quick howto.
GIMP is an open source image processing program available on macOS, Linux and Windows. Visit https://www.gimp.org/ to download and install.
If you are like me who uses macOS and have the mighty homebrew package manager installed, simply run:
brew install gimp
Start the gimp, open your image-to-be-converted, then from the menu select
On the dialog box, you want to adjust
Block Width and preview the results.