I usually use Squoosh.app to reduce the size of my PNGs, but in this case I had a folder with nearly 50 images in it so I wanted to do it using the command-line.
pngquant can reduce the number of colours in a PNG image, which I find makes a huge differente to the file size (also possible using Squoosh).
oxipng is a performante lossless PNG compressor.
I got great results by running pngquant first, then oxipng on the results.
Both can be installed via Homebrew:
brew install pngquant oxipng
Then I ran this command to reduce to a maximum of 50 colours per image:
pngquant --quality 20-50 *.png
(I don't know if the lower bound of 20 is the right thing to do here, maybe 0-50 would be better?)
This creates a file called x-fs8.png for any file called x.png.
Then I ran this to apply oxipng:
oxipng -o 3 -i 0 --strip safe *-fs8.png
The results were that a 383KB file dropped down to just 70KB. The images are visually different but the size savings are huge, which is particularly important if you plan to put 50+ images on a single web page.
Created 2021-02-07T11:57:17-08:00 · Edit