ICO (Windows Icon) file format plugin for Photoshop

Copyright 2002-7 Toby Thain, toby@telegraphics.com.au

The plugin gives Photoshop the ability to directly Open and Save Windows icon (.ICO) files. Version 1.8b4 and later can also open .CUR (cursor) files. Download the latest version here.

Tested with:

Free software - donation suggested

This program is free software licensed under the terms of the GNU General Public License. If you use this program and like it, please use PayPal to send the author what you think it is worth (US$5 suggested):

The program is fully supported. Please contact the author with any bug reports, suggestions or comments.

To install

  1. Vista notes (Due to the number of problems reported with it, Vista is NOT recommended):
  2. Move the plugin into the "File Formats" folder inside your Photoshop Plugins folder:
  3. If using Corel PSP Photo X2, put the plugin in C:\Program Files\Corel\Corel Paint Shop Pro Photo X2\Languages\EN\PlugIns
  4. Quit and relaunch Photoshop, if it's already running.

To use the plugin

Having trouble?


How to add a "favourites" icon (favicon, favicon.ico) to your web site

  1. Create the file named favicon.ico with your desired graphic, and put it at the root level of your web site. (If you want Internet Explorer to recognise it, it must be 16x16 pixels in size.)
  2. Put a tag as follows in the <HEAD>...</HEAD> section of your top-level HTML page (home page):
    <LINK REL="SHORTCUT ICON" HREF="favicon.ico">

More references:

...and many others.

About transparency

The ICO format has an inherent 1 bit transparency mask (0 = opaque, 1 = transparent), called the AND bitmap.

Saving indexed mode images

To ensure output files are as compact as possible, the smallest pixel depth is chosen sufficient to represent the colours used by the icon:

A note on file sizes (Mac only)

Do not be alarmed if the Mac Finder shows an unexpectedly large file size for ICO files saved out of Photoshop. The ICO itself is stored in the data fork and is as small as possible (see above).

The Finder's size calculation is increased by Photoshop's prolific "metadata" in the resource fork, and does not truly reflect the size of the ICO data. (This is stored for all files saved out of Photoshop, regardless of format, and whether image thumbnails and previews are enabled in Preferences.) Finder's "K" size is also affected by the volume's minimum allocation size (often 4 or 8K depending on partition size).

On upload to a web site, the data fork alone is copied and the resource fork is stripped, and so this extra data (and Finder's padded figure) has no effect or relevance whatsoever. The "true" logical size of the ICO file can be confirmed in OS X's Terminal with ls -l in the icon's directory (or files -x br in MPW Shell).

About 32-bit (Windows XP) icons

The plugin can create 32-bit icons with 8-bit alpha transparency. This will occur in two cases:

  1. in Photoshop 6.0 or later, saving a layered RGB image (i.e. not flattened)
  2. in any version of Photoshop, saving a flat RGB image with 2 or more alpha channels.

In the first case, the layer transparency will be used as the ICO alpha. The 1-bit "AND mask" is taken from the first alpha channel, or if there is no available alpha channel, is derived from layer transparency.

In the second case, the first alpha channel is used to create the 1-bit "AND mask", and the second alpha channel becomes the 8-bit ICO alpha.

In both cases, the colour data is set to zero (black) where the icon is transparent. This should produce the desired result (complete transparency over the background).

Still confused, or having trouble?

Don't hesitate to write to us.