Bulk optimize your images with smush.it

PageSpeed Insights by google told me to “Optimize images [by] Properly formatting and compressing images [to] save many bytes of data.

Download the zip then in terminal run:

java -jar /path/to/your/smushit.jar -imageDir=/path/to/your/images

Download: https://github.com/abhirama/smushit/
Source: http://gizmotronix.com/losslessly-compress-a-batch-of-images-with-smushit/