I am trying to find out the width and height of an image (a URL) transferring as few bytes as possible. This coding challenge has two separate parts:

• Finding the cheapest way to retrieve width and height.
• Verifying that the solution is indeed cheap.

The first part is not that interesting since it’s a fairly well documented problem. A bit too documented, actually, since I found several solutions:

• A naïve version using ImageIO.
• A more advanced solution using ImageReaders.
• A hand rolled solution written by Jaimon Matthew.

This last solution looks pretty efficient from a network perspective but I’m worried it might leave out a few corner cases in image handling. The first two solutions are probably battle tested and very robust but I have no idea how effective they are from a network standpoint (their Javadoc doesn’t describe the specifics of how they operate).

So… Do you have a better solution? And whether you do or don’t, how would you assess how many bytes these implementations transfer?