[Closed] Image optimisation?

There's a bunch of free tools that can do it for you:
http://mashable.com/2013/10/29/image-compressors/#RBRdDxDhsPqc

I've heard that imageoptim is good but I haven't used it myself:
http://imageoptim.com/

What do you mean by “optimise”?

It could mean improve the look of the image somehow (brightness etc), the resolution (for hi resolution displays), how large the file is to download, lots of things.

It might also mean creating multiple image derivatives to serve up an appropriately sized image to different devices, like Drupal 8 does, using Responsive Images configuration.

Rachel