You should add an image to your article with an alt tag and alt tag must contain the main keyword of your article, this process is called image optimization.

Image optimization is a function of lossy and lossless compression. Differences in image formats are due to the difference in how and which lossy and lossless algorithms are used to optimize the image.

The OP is asking for the image optimization not the image compression. :no:
You are self acclaimed seo expert and doesn't even know what is it. :rolleyes:

Image Optimizing is a process of sending the high-quality images in the proper format, dimension, size, and resolution while we keeping the smallest possible size.