Note this is not the best download speed indicator. However it is reasonable to assume that this is the real feel of your download speed when you are browsing as the content delivered to your browser is coming from remote server and that server's bandwidth may be limited
This is an alternate to other speed test apps
To get the size of the image file ...
1. You can download the image in your system and get the size from file properties
2. Use Image search in Search Engines to determine the size of the images from your favorite sites
3. Can be used during travel to check the Internet download speed