Windows Icon files thumbnails

[sailor]

I have a bunch of .ico files and it used to be that the icon of each file was the icon contained in the file. Which makes sense. But something happened and now that does not work. How do I restore it so that each file's icon is the icon in the file?

[Mbossa]

Which version of Windows are we talking?

[sailor]

Windows XP Pro SP3.

[sailor]

This problem is only in one machine; the rest do not have it. So I am looking around in the registry to see if I can locate any suspicious difference but cannot find anything. All have the same entry:

HKEY_CLASSES_ROOT\icofile\DefaultIcon @="%1"

which seems to point at the file itself but it is not working in one machine.

[sailor]

After some fumbling around in the registry it is now working again. I am not entirely sure what change I made which fixed it.

I know how to make a .ico file with a single icon graphic but does anyone know more about the structure of icon files, how to have several icons in the same file, how to have alternative icons in different sizes, etc?

[blank]

Originally Posted by sailor

After some fumbling around in the registry it is now working again. I am not entirely sure what change I made which fixed it.

I know how to make a .ico file with a single icon graphic but does anyone know more about the structure of icon files, how to have several icons in the same file, how to have alternative icons in different sizes, etc?

They are basically a BMP file with a slightly different header (though windows doesn't seem to take any notice of the header). http://en.wikipedia.org/wiki/BMP_file_format

[sailor]

Originally Posted by blank

They are basically a BMP file with a slightly different header (though windows doesn't seem to take any notice of the header). http://en.wikipedia.org/wiki/BMP_file_format

I believe that is only true to such a very limited extent that one may say it is not really true.

If you take a BMP file and change the extension to ICO then Windows will be able to use it as an icon. Maybe originally that was all there was to it but now it is quite different.

As far as I know BMP files can only hold one image while ICO can hold several images, plus alpha transparency channels plus ICO also recognises PNG format, not only BMP.

I have no problem making basic single image icons using Irfanview but I do not know how to make a single ico file hold several different icons. Also, Windows sometimes does not shrink the icons well and they look bad. I know some programs have multi-sized icons so that the 32x32 is used on the desktop, the 16x16 is used in windows explorer detailed view, etc. This way the 16x16 is not merely the larger one shrunk by windows but is a separate icon included in the same ico file as the larger one.


That is what I'd like to do.