Google requires the webpage to load in less than a few seconds to give you a first page rank in the search results. Therefore, you need a tool to optimize the size of the image before inserting the illustration into WordPress.
ImageOptim
ImageOptim is a free image optimization tool.
Comparing the result with different tools
Alternative solutions
Battle of the image compression wordpress plugins
TinyPNG, EWWW Image Optimizer, and Kraken.io go head-to-head. The results depend more on what your needs are (as always!).
Compression Plugin Review: Smush Pro vs Kraken vs EWWW
For years now, WP Smush has been the most popular free image compression plugin for WordPress with more than 200,000 active installs.