Take into account this icon: http://www.flobi.com/test/floIcon/show_all.php?sid=d65f1f5ca84e7a8d478b1cc4805ee94e_3 . Resizing the donkey to 16×16 makes the image practically indistinguishable (bad icon file). On the other hand, this icon: http://www.flobi.com/test/floIcon/show_all.php?sid=898b0f4ffbd8fb442d3597b48495b192 . Resizing that design also gets hard to view at 16×16, but an alternative has been provided representing the same (or similar) idea for the smaller lists. You can’t do this with any other popular image format (as far as I’m aware).

This is not perticularly useful in a web environment as far as I’ve seen, save perhaps favicon files, because in web design, usually there is a very specific environment. Images are sized specifically for the space to which they are assigned.

It is interesting that you mention PNG’s because the new Vista .ico file format utilizes PNGs internally. That is, the images saved inside the icon file are stored as PNGs (whereas the old format stores the image as a modified uncompressed BMP). This allows the icon file to utilize PNG’s compression capabilities. That is important because icons are getting bigger. Though even the old format technically supports icons 256×256 and bigger, without the compression, the file size can get pretty big.

Oddly enough, using PNG’s effectively eliminates one feature that I think is unique to the ico format and that is what I’ve dubbed “Inversion Method” (I’m not sure what the real term for this is because I’ve never seen it talked about before) you can see what this is in section III.g. on http://www.flobi.com/test/floIcon/more_on_icons.php . But no one uses this feature anyways.

I also thought about extracting icons from EXE files when trying to imagine some uses for this library – this might be useful for software directories and similar sites.

While the .ICO format may be versatile I’d say it’s use is going to remain confined to a very small number of niches. It’s even possible that eventually most applications would use some other – more general purpose – image format in place of standard icons (PNG comes to mind).

Unlike most of the classes on phpclasses.org, this class was designed to be a library (the real purpose of a class), not a standalone application or a copy & paste webscript. There is no way it could stand on its own, and it wasn’t designed to. I have written a simple interface (which you can see on my website) demonstrating the extraction and assembly capabilities for which this library was designed. And as you can see, people try to assemble full size photographs or pictures they find on the web that are not even standard sizes.

There is a lot of misunderstading with the public about icon files, however, the icon format is a very versitile format (even storing those non-standard sizes). In my opinion, none of the generator/managers I’ve seen are really up to snuff (and very few of the icon libraries). My hope is that with easy access to this versitile format, someone will create something that is up to snuff.

Thank you for analyzing my class. I agree it is interesting and it was a lot of fun to write. I plan to make one for Vista images, but so far, I’ve not got Vista…and haven’t been perticularly impressed with what I’ve seen of it. I also plan to make a DLL assembler & EXE/DLL/etc extracter for icons in that format too, but so far I haven’t had the time.