Very good info in the article. I recently discovered a tool called Kraken for optimizing images. Takes the drudgery out of what could be a very tedious task. I was able to optimize all of the images on my WordPress website in a flash. They also support web uploading images, I believe Dropbox and other methods.
Now, Kraken doesn’t resize images for you, but compresses them just right and removes unneeded data from the images. Typical savings for already compressed images was around 40% for me. Anyway, here is the link: https://kraken.io/
Enjoy!