For general web development questions that are not specifically related to CSS HTML Validator. This includes (but is not limited to) general HTML, CSS, Accessibility, JavaScript, and SEO questions.
If you want to reduce the size of the image file to reduce the number of KBs (bytes) that are transferred then you will need to reduce the image size of aaa.jpg using an image processing program. Unfortunately, neither one of those options you mentioned would do that.