This plug-in will work for any PhotoShop version from 5.0 onwards for Windows, and a handful of versions for Mac (it depends on the OS X version). If for some awful strange reason, you’re using Windows 98, you can download an alternative build of the plugin.
Mac Compatibility
Photoshop CS5 on Intel Macintosh (32/64 bit)Photoshop CS3 & CS4 on 32-bit Intel and PowerPC MacintoshPhotoshop 3.0-7.0, CS, CS2 on PowerPC Macintosh (OS X, OS 9 and Classic)Photoshop 4.0 / MacOS 8.0 on 68K Macintosh
Windows Compatibility
Windows: Photoshop 5.0 and any later version on Windows 98/NT, XP, Vista, and Windows 7
Requirements
ICO file format plugin for Photoshop
To install
32-bit / 64-bit Windows (Vista/Windows 7):
Download the plugin and extract it to a folder. Move the plugin file to C:\Program Files\Adobe\Photoshop\Plug-Ins\File Formats, or the 32-bit version if you’re on 32-bit Windows (C:\Program Files (x86). You may need to create the File Formats folder inside \Plug-Ins if it does not exist.
If you are running on a 64-bit Windows system and are launching the 64-bit version of Photoshop CS4 or CS5, download the 64-bit version of the plugin and put it in the Plug-Ins folder corresponding to 64-bit Photoshop (i.e., the one in “Program Files” not “Program Files (x86)”). Move the plugin into the “File Formats” folder inside your Photoshop Plugins folder:
For Windows (32-bit), 8biFor Windows (64-bit), 8bi
If using Corel PSP Photo X2, put the plugin in C:\Program Files\Corel\Corel Paint Shop Pro Photo X2\Languages\EN\PlugIns Quit and relaunch Photoshop, if it’s already running.
To use the plugin
Use Photoshop’s Open command (File menu) to open .ICO and .CUR files (which will now appear in the file browser)Use Photoshop’s Save command to create .ICO and .CUR files.If saving .CUR, note that the cursor hotspot is defined by the ruler origin.
Having trouble?
If you are not sure if the plugin is correctly installed, look for “ICO (Windows Icon)” under Photoshop’s “About Plug-in” menu (on Windows, look under “Help”; on OS X, under “Photoshop”). If it is not listed:Check you have downloaded the correct version (Windows/Mac)Is it in the “File Formats” subdirectory of Photoshop’s “Plugins” folder?Have you quit and re-launched Photoshop?If you are running Vista and see the error “plugin entry point not found”, try restarting and reinstalling, or see this post.The plugin is not a Filter or Import/Export plugin, so don’t look for it there. It appears as a format option when Opening or Saving (eligible images).The ICO format does not allow images more than 256 pixels high or wide.Only Bitmap, Grey Scale, Indexed and RGB mode images, no more than 8 bits per channel, can be saved as ICO.
About transparency
The ICO format has an inherent 1 bit transparency mask (0 = opaque, 1 = transparent), called the AND bitmap.
When reading or saving an RGB mode image in Photoshop 6.0 or later, layer transparency is used for the maskIf the image is Indexed mode, and uses a “transparent index”, this will be used to set the icon maskIn other cases, the ICO mask is treated as an alpha channel (black = 0 = opaque, white = 255 = transparent)In PNG (Vista) format icons, the alpha channel is simply stored as part of the PNG. There is no separate mask.
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:
RGB mode: no colour tableIndexed/Grey Scale mode with >16 colours: 8 bits per pixel (up to 256 colours in colour table)Indexed/Grey Scale mode with >2 colours: 4 bits per pixel (up to 16 colours in colour table)Bitmap or Indexed/Grey Scale mode with 2 or fewer colours: 1 bit per pixel (up to 2 colours in colour table)
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: 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).
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