Thats right, image name, image alt tags, size of the image all come under image optimization.

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Yes, image file name adds value to your image and such image adds value to your content or web page. In our SEO practice, we never forget to give a pertinent file name to image and also give alter tag (same as file name) at the time of attaching image. And because of that, two or three articles of my website receives number of visitors everyday. Images which I have attached with those articles ranks on the first page for highly competitive keyword like "things to see in goa", "economy 7 energy meter". Visitors click on the images and read the posts.