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You are here: Digitope.com > Pixelshop > In Depth > Alpha Icons
About the alpha 32-bit icon format
This article gives you the technical information about the 32-bit icon format introduced with Windows XP. Although this article looks confusing, rest assured that working with alpha icons with Pixelshop is easy and transparent. This is simply an overview of the format.
About the format
The Alpha icon format, introduced with Windows XP, gives icons multiple levels of transparency. This allows icons to have a smooth effect, and reduces the jagged edges normally present with icons.
On the left we have a 256 color icon (no alpha), and on the right we have an Alpha icon. Notice how the Alpha icon appears to blend into the background.
Comparisons
Before we go into more detail, let’s first look at a comparison between 256 color icons and Alpha icons.
256 color icons shown against various backgrounds.
Alpha icons shown against various backgrounds
From the two images above, you can clearly see how the Alpha icons appear to ‘blend’ into the backgrounds, whereas the 256 color icons have a ‘cut-and-paste’ appearance.
So, what exactly is Alpha?
First, let’s look at normal transparency in icons. To achieve transparency (where the background shows through) a mask must be used. This is simply a monochrome icon included with your icon, with black representing transparency, and white representing opaqueness. When the icon is drawn on your screen, this mask is used make the icon seem transparent.
A representation of an icon and a mask.
Normal, non-alpha icons simply have a black and white mask. Either the the individual pixel is 100% opaque or it is 100% transparent. This gives a blocky look to some icons.
The difference with alpha icons is that they have a grayscale mask, where black is transparency, white is opaqueness, and grays are varying levels of transparency. This both removes the jagged edges, and allows convincing shadow effects.
An example of a normal mask and an Alpha mask.
What does all this mean for me? How do I use alpha?
You don’t have to create special masks for icons; Pixelshop does all this for you. If you’re converting an image without transparency, a high-quality Alpha channel will automatically be created using Pixelshop's advanced algorithms. If you’re importing a Photoshop image or transparent GIF, Pixelshop will use the Alpha in the file.
If you’re just drawing, simply slide the Alpha slider (next to the color swatches) to adjust transparency.
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