Icon in Windows Vista Explorer
Windows Vista Explorer makes use of high-resolution 256x256 icons. While 256x256 pixels seem to be too much for current displays, Vista is able to dynamically downscale images to any size. By using large icons, Vista Explorer is already prepared for future displays with higher resolution [DPI].
The image size is controlled by a slider control in Windows Explorer. This slider replaces the discrete view modes in Windows XP. Vista makes it possible to assign different view mode and different icons sizes to each folder.
Support for high resolution icon is not limited to system icons. Our test showed that a custom icon with a large image is accepted and used by Windows Explorer without problems.
PNG Compressed Vista Icons
A typical Vista icon contains 12 images:
The ability to put 256x256 pixels image inside an icon is not new. This feature was available in Windows XP and in previous systems. The problem is that an icon with all 12 formats requires more than 400kB. This is considerably more than a typical Windows XP icon needs (approx. 25kB). Microsoft solved this problem by extending the icon format.
- 16x16 pixels in 16 colors, 256 colors, and truecolor+alpha
- 32x32 pixels in 16 colors, 256 colors, and truecolor+alpha
- 48x48 pixels in 16 colors, 256 colors, and truecolor+alpha
- 256x256 pixels in 16 colors, 256 colors, and truecolor+alpha
Vista icons store the images in icons using PNG compression. With PNG compression, the size of an icon is reduced. Because PNG is loss-less and supports 8bit alpha channel, the quality of icon is maintained.
Current Vista icons use compression for the large 256x256 formats only. This makes the icons backwards compatible with previous systems. Windows XP will ignore the high resolution images and load the standard 48x48 pixels images. It is possible to compress all images in an icon. Such icons will occupy even less space and they will work without problems in Vista. They will of course fail under Windows XP.
Creating and Converting Compressed Icons
Vista compatible icon editor is needed to work with Vista icons. Icon editor authors are adopting the Vista enhancements to the icon format and some of them have already managed to release new version of their software. A Vista icon is created by simply adding a high resolution images and by selecting the Vista format when saving an icon.
Some editors allows extracting Vista icons from executable files and converting them to XP icons (e.g. saving them without compression).
Microsoft improved the visuals of Windows delivered a future-proof solution compatible with high-end system as well as with lower definition screens. The 256x256 icon images allow icon authors to add more details and make the icons more appealing under wide range of conditions.
The information in this article is relevant for Windows Vista Beta 1. Vista icons specifications are preliminary and subject to change.