Which graphic format to use for icons?

Which graphic format should the icons be crafted in?

A bitmap icon (like GIF, PNG, TIFF, etc.) contains only pixel-by-pixel graphic information. Pixels (constriction for "picture element") are the smallest squares of light that your computer screen is made up of. A 24x24 pixel icon picturing a plain red square is actually comprised of 576 separate pixels, each represented by little bits of numeric data in an image file. A bigger icon requires even more pixels, leading to more binary information, and a greater file size as a resilt.
A vector icon file (such as EPS, SVG, etc.) consists of mathematical-based information. A vector file containing a red square scaled to 24x24 pixels only contains numeric datd regarding the geometrical position of the fout corners of the square, information about the color of the square, and information defining the size of the square as 24x24 pixels on the monitor. That means our red square in vector format only requires about six tiny bits of data as opposed to our 576 bits of data required for our bitmap red square.
The explanation is actually a bit more complicated than it's described, but you understand the idea: Modifying the size of a vector graphic file from 24x24 to 48x48 only takes the editing of one bit of data (the dimensions). The math does the rest. However, modifying the dimensions of a bitmap image file from 24x24 takes the extra 1728 pixels, resulting in a larger file size.
Therefor one vector file can represent it's content at numerous sizes, whereas a bitmap image may only accurately represent its only pre-defined pixel size.
So if a vector file can be scaled to represent any dimensions it so desires, why do the icon desigers choose bitmap format for their icons?
If you look at the same icon, crafted in both bitmap and vector formats, you will see that the bitmap one is clear and crisp, with all the lines sharply defined. While all the icons that had been resized from the vector image look blurry.
This happens because, even though vector images can be resized, there is a weakness in them This weakness is more obvious at toolbar sizes. Especially resolutions under 48x48 pixels. The weakness is that computer screens still have pixel-based (that is to say, bitmap-based) displays.
When you take a vector file, originally sized at 24x24 and scale it down to 16x16, the relative proportions change. There's no chance you can evenly arrange 24 pixels of data into 16 pixels of space because, there's no such thing as half a pixel. So the image blurs.
There's also no way you can evenly scale 24 pixels of data upwards into 32 pixels of space. Again, the image blurs.
Even more, if you have that same vector image, originally sized at 24x24 and size it up to 48x48, you're now doubling the proportions. You no longer have sharp 1-pixel lines. You have chunky 2-pixel lines. Size it up larger (to 96x96, for instance) and those lines end up even thicker.
There are a few caveats: First, if you're creating larger icon sizes (say, bigger then 48x48) you will not see the difference as much, and you may find the results acceptable. Second, your mileage will differ as you create various types of icons. The less-detailed your image is, the less you have to worry about vector rescaling.

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ArtIcons Pro can find, extract, edit and create Windows icons in color depths up to 16 million colors. Import and export icon images, create and handle icon libraries. It supports the new icon format introduced in Windows XP (8-bit transparency). Download it

IconXP can edit and create Windows icons in color depths up to 32-bit True Color. It supports the new icon format introduced in Windows XP (8-bit transparency). You can customize desktop and folder icons. Download it

IconUtils is a complete icon and cursor solution. IconUtils package can edit icons and cursors, manage icon and cursor libraries, convert icons into images (in various graphic formats) and vice versa, customize Windows desktop and folder icons. Download it

Icon to Any allows you to convert Windows icons and cursors into BMP, JPG, PNG, GIF, ICO, CUR, WBMP and RC formats. It has a wizard interface. It's simple to process multiple files at once. You can find icons and make images for use on Web pages. Download it

ArtCursors allows you to edit Windows cursors in color depths up to 16 million colors. You also can search files and folders for cursors, import and export cursor images and create cursor libraries for better and more efficient storage. Download it

AhaView supports all popular graphic formats, including JPEG, GIF, PNG, BMP, ICO, CUR, ANI, WBMP. You can browse images in thumbnail mode, view pictures full screen with zooming features, convert images to JPEG, PNG, BMP formats and manage files. Download it

CustomIcons is an ultimate tool for customizing the icons on you desktop, in Windows Start menu and many other locations. Using CustomIcons you can easily replace default Windows icons with the ones to your choice. Download it

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