>In fact, there seems to be no choice at all as Image::Size can only output size, not change it.
It seems an important question is whether you want to mess with the size(pixels) or the weight(kilobytes). If all you're trying to do is change the *html display* size , I've used
Image::Size
succesfully for this.
What you've created there is called a dumbnail (as opposed to a thumbnail) and is generally considered bad practice. The web client still has to download the big file, so its not the prefered way of displaying a smaller image.