Icons in Windows XP

This article answers basic questions about icons. How do icons differ from images? What's the structure of an icon? How are icons distributed? What's the difference between Windows XP icons and older icons?

To understand this article you should already know basic terms related to computer imaging, namely pixel, image resolution, color depth, and image file format.

What is an Icon?

A computer icon is a graphical symbol that represents a property, function, or entity. In computer applications, icons are used to quickly execute commands or open programs and documents. You access the functionality behind an icon by clicking or double-clicking it. Operating systems often allow you to customize visuals of various objects by applying your own custom icons.

You may obtain icons from various sources (for example from our icon library) or you can build your own. If you choose to pursue the more difficult but more rewarding path (creating your own icons), you will need to know more than what was already said. In this introduction to Windows XP icons, you will learn:

What are the differences between an image and an icon?

Icons are often compared to images. This comparison is not entirely fair. It is like comparing shoes to leather. Shoes may indeed be made of leather. Shoes may be considered a specialization of leather with some added bells and whistles. But then there are shoes that are not made of leather... An icon (graphical symbol) can easily be represented by an image. But this could, and probably would change. In future version of your operating system, icons may be using animations or even 3D models. Icons would still be graphical symbols, but not images anymore. For now, let's get back to year 2005, where icons and images are closest friends.

A computer image is a raster (composed of pixels) or vector (composed of lines, rectangles, circles, etc.) picture. It may have arbitrary size, resolution and color depth. It is stored using one of the standard formats (BMP, PNG, GIF, JPEG, TIFF, ...).

Icon is composed of arbitrary number of images. This is because icon must be usable under wide variety of conditions. Icon should look good on high-resolution LCD as well as on a ten years old monochromatic monitor. There are multiple images inside an icon, each optimized for best experience under specific circumstances.

Images usually have rectangular shape, icons on the other hand do not. When you put an icon on your desktop, it appears to have arbitrary shape and you can see background around that shape. Internally, the icon still has a rectangular shape, just like an image. But icons always support per-pixel transparency, which means that any pixel can be marked either transparent or opaque.

What is the structure of an icon?

We have already mentioned in previous paragraph, that an icon is composed of several images. They have different sizes (or resolutions) and color depths. Windows defines standard sizes (16x16, 32x32, 48x48) and standard color depths (16 colors, 256 colors, 16.8M colors), that should be present in any general-purpose icon.

It is very important to create several image formats in an icon (especially if you whish to redistribute it) in order to be compatible with all screen configurations.

How does Windows use the various sizes and color depths?

If an image format is missing, Windows displays the nearest existing image. It works but quality suffers.

How are icons distributed?

There is a standard file format for icons in Windows. Icon files always have .ICO extension. A file in this formats holds all icon images. Microsoft also recommends how the images should be ordered inside an icon.

Icons can also be embedded inside an application (.EXE), application extension (.DLL), or other executable file. This option is used quite often by application developers. Icon editors are usually able to extract icons from applications.

There is one more file format related to icons. It is called Icon Library (.ICL) and its sole purpose is to have multiple icons in one file. We consider the value of this format negligible, because anyone can get similar or better results by zipping icons or putting them into an ordinary file-system folder. Let us know, if you have different opinion.

What about the new Windows XP icon format?

There actually were no changes to the icon format when Windows XP was released. Windows XP is just able to make use of a high quality image format in an icon. In this format, each pixel has one of 16M colors and one of 256 levels of transparency. That means, a pixel is no longer either opaque or transparent. Now it can be semi-transparent. The transparency level is called alpha channel.

Conclusion

To practise your new knowledge, open an icon in RealWorld Icon Editor. Try making changes to it and watch Windows reacting to them.

Recent Comments

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Anonymous
on September 2nd 2009

good

Anonymous
on September 29th 2009

I work for a dildo boss who knows nothing about computers, refuses to pay a tech to come out, and expects me to be (poof!) an expert without training. Now he's ragging on me to know the difference between icons (images?) in our Network Places folder. I keep telling him I know nothing, but he ignores me -- it's all about the mighty dollar. He's claiming that a bunch of icons have shown up in "My Network Places" since I came to work here back in June. I keep telling him that I'm not deleting anything because he'll accuse me of screwing up the computer, but he won't listen. Can anyone direct me to a site where I can learn something to the effect of my responsibilities as the network administrator? I'd very much appreciate any help. Thanks,

dael
on September 29th 2009

Perhaps he is wondering if you know what those icons in that folder represent. Icons, in general, represent programs, or files, or any "object" on the computer. It can represent a location on the internet as URL/internet address. Icons are just symbols for computer objects. What they represent is either basic information and/or it may take a program or application on the computer to open it. as in a text (.txt) file is opened with notepad. The icon represents that text and is a file on the hard drive. The computer opens notepad, goes to that file on the drive and renders it in a readable format in the window.

Anonymous
on October 14th 2009

Soz Peepz Bwt Want to noow what is an icon is my thing rite or rong check: An icon is a graphic image, a small picture or object that represents a file, program, web page, or command. Icons help you execute commands, open programs or documents quickly.

Anonymous
on October 22nd 2009

Thanks dael. So far your explination makes the most sence for the answer I was looking for.

Anonymous
on October 28th 2009

This is a good description of XP icons.

Anonymous
on November 11th 2009

How can you be over complicating what an icon is. The icon is just 'the picture' that is being displayed on the file you have i any given folder (And indeed the folder picture itself)

If something new is in there then it is a 'folder', 'file' or 'shortcut'(be it URL address or other file path pointer)

The description which is listed above is very detailed and a helpful description - even to myself - for how windows uses, or people can make icons, but the 'icon' is just a picture. it does nothing else. What ever it is sitting on your bosses computer is one of the 3 stated objects above.

Thanks for the icon description Mate!!! Good Job!!! :D - Dazzr

Anonymous
on January 20th

love it

Anonymous
on February 2nd

If new "icons" are showing up under your bosses "Network Places" folder then that indicates he has gone to a network resource (ie - shared network folder) and Windows is saving that as history so he can easily get back to that location. You can also set these up manually as bookmarks if you like.

Anonymous
on February 18th

Download Icolover and click Search icons.

What is a Windows XP icon?