Talk:ICO (file format)

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Removed link to IconConstructor Software - "allows to create Windows icons from any image for those who have no design skills"

256x256 support added in Vista incorrect[edit]

I have personally built icons using my own custom icon creation software and Windows XP will correctly read icons which are 256x256 and even larger. Though it does not have any avenue in which to display them natively, if no other image is available, one can be read by Windows and resized to fit its needs.

Nonetheless, Windows XP does support storage of files at and larger than 256x256 pixels. As this is demonstratable, [1], I have updated the page to reflect this. I also updated the page to correctly portray the requirements of the AND bitmap in 32-bit images. --Flobi (talk) 08:10, 21 March 2009 (UTC)

In the directory entry, icon sizes are stored in an 8-bit unsigned integer. How do you propose an icon larger than 256x256 is stored? Would it just be 0, and then the BMP header shows that it is larger than 256x256, as with the color counts of images with more than 256 colors? Either way, we're digging into the area of original research here. Λύκος 23:22, 21 March 2009 (UTC)
That would be correct. In fact, I have personally tested this. I have raised the dimension limitation on my icon assembler [2] to 300x300 if anyone would like to see it in action. In fact, here's a 300x300 test: [3]. I guess you could say that I am doing original research on this, not specifically for Wikipedia, but when I noticed this page, I figured I'd share. I'm also looking into the possibility of using the 4th byte of the palette for alpha transparency [4], the effective nature of inversion [5] and a number of other things. Actually, every piece of info on this page: [6], I have personally verified or uncovered. --Flobi (talk) 13:34, 26 March 2009 (UTC)

Using big-endian? Dubious[edit]

Does the ICO format use big-endian format to store its data? Intel typically uses little-endian, so the phrase "big-endian (Intel standard) format" seems doubly-wrong to me. -- pne (talk) 10:51, 12 February 2008 (UTC)

Given that the MS sample code pays no attention to endian issues and MS pretty much exclusively targets little endian systems I think it's safe to assume it is little endian and whoever stated it was big endian was wrong. Plugwash (talk) 02:01, 13 February 2008 (UTC)
Agreed. I have disassembled an icon, and assembled some of my own, and Plugwash was right: icon headers are in little endian format. Also, the xp graphical shell supports up to 96x96 icons, in the filmstrip or thumbnail views. Apocalypse r (talk) 20:40, 22 July 2008 (UTC)
True, but see here: Talk:BMP file format#Byte_order_and_bit_order. Shinobu (talk) 12:58, 19 December 2008 (UTC)
I do not know who talked about BMP possibly being in big endian, but in general they are in little endian. It is possible that you can save BMPs in big endian, but I don't recall support for that in that format (RLE from SGI supports both endians... so does TIFF which either starts with II or MM depending on the endian used in the file) Alexis Wilke

Support for image/[edit]

After some experimentation I found out that neither IE7 nor Opera nor Firefox only latest Opera and Firefox has support for image/ mime type. IE7 and older browsers don't, and will fail to render such files. Yet all work with image/x-icon just fine. Even Microsoft's own homepage server sends identification for its favicon as image/x-icon. Why don't they use the type they themselves registered? Apache 2 shipped with a default mapping of .ico to microsoft's mime-type (this is how I discovered it). But recent versions also dropped this idea and now use x-icon too.

So, is image/ dead? Theultramage (talk) 09:47, 13 April 2008 (UTC)

Obviously Micrsosoft doesn't use image/ because of lacking browser support, not just their own but also other vendor's.
Why didn't they patch Internet Explorer to support it yet? One presumes that they currently have other priorities, if you know what I mean.
So is it dead? Well, WP:BALL. Shinobu (talk) 13:08, 19 December 2008 (UTC)

Microsoft didn't register image/ I have added reference to confirm this. (talk) 16:30, 15 April 2013 (UTC)

Originally 32×32 pixels square and using 16 colors[edit]

Are you sure? Because icons can store even monochrome images. Shinobu (talk) 12:49, 19 December 2008 (UTC)

I know 16 color icons were supported in 3.x, I don't know about before that. Plugwash (talk) 18:55, 22 January 2009 (UTC)

Section Icon sizes, color depths, and transparency data: Unclear and rife with weasel words[edit]

Hi everyone.

Summarily, the problems include:

  1. This section uses weasel words
  2. This section uses the unclear terms "native mode" and "native support". It is unclear as to what is the distinction between native and non-native and to what these terms apply.
  3. This section uses the term "apply" to describe the use of XOR and AND bitmaps but does not explain how exactly they are applied. I still do not under stand what is the use of XOR or AND bitmaps.
  4. This section uses the term "overflow read" which is not described and probably is a weasel word.

Here is copy of problematic areas tagged:

Originally[when?] 32×32 pixels square and using 16 colors, more recent versions[which?] of Microsoft Windows support icons at multiple sizes and color depths...

Icon image data 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.[clarification needed What does "applied" mean?]

... however it is still required as Windows XP can and will use a 32-bit image in 24-bit mode by removing the alpha channel and applying the AND bitmap for transparency if no 24-bit image is available. If the AND bitmap is not included, the AND map will be assumed in an overflow read, producing an undesirable transparency pattern.[clarification needed What is "overflow read"?]

Windows XP can read 256×256 pixel icon images and larger and it can resize them to use if no closer image size is available, but it has no native mode for common usage of these sizes. [clarification needed What is "native mode"?]

Windows Vista adds support for natively displaying 256×256 pixel icon images...[clarification needed What is "native mode"?]

ICO files can be edited or exported with a number of graphics programs, among them GIMP, CorelDraw, IrfanView and Paint.NET (via a plugin[which?]).

Fleet Command (talk) 13:42, 4 November 2009 (UTC)

PNG info is not necessary here[edit]

file types for icons include: ico, png, bmp, gif, icns. there's no need to explain all the others here, and so there's no need to explain png. —Preceding unsigned comment added by Johnywhy (talkcontribs) 02:41, 23 September 2010 (UTC)

Where is your source? Fleet Command (talk) 10:42, 2 May 2011 (UTC)

Personally, i have lots of icon in TIFF format, exploiting its capability to store multiple raster images per one file. And what difference it makes? There are dedicated format for icons, there is no reason for endless list of format which potentially can contain an icon. Therefore, PNG is marginally (given that it satisfies true-color and transparency capabilities) offtopic here. Ugh, your bot is quite unfriendly.

CUR is not necessary[edit]

It's almost a bit of advertising to have the CUR format mentioned, especially when there is no page referencing this technology. The article is about .ICO. —Preceding unsigned comment added by Rajpaj (talkcontribs) 05:21, 2 May 2011 (UTC)

Disagree. Articles in Wikipedia must be broad in coverage and CUR has so much similarity of context with ICO that must be covered. Advertisement only applies to either competing products or subjects of insufficient similarity of context. Fleet Command (talk) 10:42, 2 May 2011 (UTC)


The first link in the references section aggressively attacks visitors with sucksass with buying whatever their merchandise displayed instead of actual content. Since it is just another wordpress website i suggest to replace with more friendly source. — Preceding unsigned comment added by (talk) 04:04, 25 December 2011 (UTC)

Icon library section[edit]

... lacks the facts. Who proposed dummy resource only executables? When? Why? — Preceding unsigned comment added by (talk) 22:39, 14 September 2012 (UTC)


I was just thinking: why is this article called ICO (file format), but the one on IPA called .ipa (file extension) George8211 conversations 21:32, 15 October 2013 (UTC)

MIME type[edit]

About these recent edits by User:�, which were made to "remove POV-pushing", "look more neutral", and "let the reader judge":

  • The citation for the statement "Until version 11, Microsoft Internet Explorer required the type image/x-icon instead" was removed, then "[not in citation given]" was added. The original citation states "IE11 dropped the type attribute requirement." In other words, IE11 and later don't care whether you say image/x-icon, image/, or something else entirely.
  • Linux, Microsoft HealthVault, and the Apache web server (on any operating system) use image/ Note that the existence of Microsoft software using image/ makes the newly readded statement "image/ not recognised by Microsoft software" misleading at best. The only current software I can find that doesn't use image/ is Microsoft IIS, which is still using image/x-icon.

I absolutely agree that image/x-icon should be mentioned in the article, but portraying it as an equally respected alternative gives it undue weight. —Remember the dot (talk) 05:51, 2 March 2014 (UTC)