ICO (icon image file format)
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| ICO | |
| File extension: | .ico |
|---|---|
| MIME type: | |
| Uniform Type Identifier: | com.microsoft.ico |
| Developed by: | Microsoft |
| Type of format: | icon graphics file format |
| CUR | |
| File extension: | .cur |
|---|---|
| Developed by: | Microsoft |
| Type of format: | cursor graphics file format |
The ICO file format is an image file format used for icons in Microsoft Windows. The CUR file format for cursors is identical, save for a different identification byte in the header.
It contains one or more small images at multiple resolutions and sizes each of which is made up of two bitmaps: the AND bitmap and the XOR bitmap. The AND bitmap is 1 bit per pixel and is applied first to decide which areas of the image are affected by the background. The XOR bitmap is then applied using XOR. This allows for transparent areas in the image but also allows for inverting the background and other tricks. Originally 32x32 pixels square and using 16 colours, more recent versions of Windows support icons at multiple sizes and colour depths. Current icon files hold images of typically 16x16, 32x32, and 48x48 pixels at 4, 8, and 32 bit colour depth. For the width and height of an icon are stored in one byte each, the size of an icon can range from 1x1 pixel up to 255x255 pixel. When using 32 bit icons with Windows XP, transparency is taken from the alphachannel of the image allowing seimitransparent areas like shadows and antialiased edges.
The official IANA registered MIME type for ico files is image/vnd.microsoft.icon. Before this was registered image/x-icon was the accepted option that complied with the rules of using x- for unregistered tokens. However, many others are seen, including image/ico, image/icon, text/ico, and application/ico. Many web servers do not come configured with a mime type setting for .ico files, and may send their default mime type which might be text/html or text/plain.
[edit] Icon library
An icon library, or "ICL", is a way to package Windows icons. An ICL is a NE format Windows binary with ICON resources representing the packaged icons.
[edit] See also
- Windows bitmap - A very similar file format
- (Note that many of the external links in that article are relevant to ICO files as well).
- compare: Apple Icon Image
- Wikipedia:Icons
- Favicon
[edit] External links
- IANA registration information for image/vnd.microsoft.icon
- Explanation of the ICO implementation from Microsoft
- Microsoft's Guide for creating icons
- "Complete Icon Format Explanation" by ALFONS HOOGERVORST: Technical details included.
- Short guide to using ICO files.
- Compare with Mac OS X Icons
- Online .ICO Editor
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