Question

I need to write a program that will generate 108 combinaisons of icons (standard windows .ico files) based on a tileset image.

I use the class System.Drawing.Bitmap to build each combinaison, and I save them like this:

Bitmap IconBitmap = new Bitmap(16, 16);
// Some processing, writing different parts of the source tileset
// ...
IconBitmap.Save(Path.Combine(TargetPath, "Icon" + Counter + ".ico"),
                ImageFormat.Icon);

But I found out that the file saved is actually a PNG. Neither Windows Explorer nor Visual Studio can display it correctly, but GIMP can, and if I open it in an Hex viewer, here is what i see:

00000000  89 50 4E 47 0D 0A 1A 0A 00 00 00 0D 49 48 44 52  ‰PNG........IHDR
00000010  00 00 00 10 00 00 00 10 08 06 00 00 00 1F F3 FF  ..............óÿ
00000020  61 00 00 00 01 73 52 47 42 00 AE CE 1C E9 00 00  a....sRGB.®Î.é..
00000030  00 04 67 41 4D 41 00 00 B1 8F 0B FC 61 05 00 00  ..gAMA..±..üa...
00000040  00 09 70 48 59 73 00 00 0E C3 00 00 0E C3 01 C7  ..pHYs...Ã...Ã.Ç
00000050  6F A8 64 00 00 00 15 49 44 41 54 38 4F 63 60 18  o¨d....IDAT8Oc`.
00000060  05 A3 21 30 1A 02 A3 21 00 09 01 00 04 10 00 01  .£!0..£!........
00000070  72 A5 13 76 00 00 00 00 49 45 4E 44 AE 42 60 82  r¥.v....IEND®B`‚

Also if I rename the .ico to .png Windows Explorer can display it properly.

I have this result even if I do NOTHING on the bitmap (I construct it with new and Save it directly, that gives me a black png).

What am I doing wrong?

I also tried this, which gave me awful 16 color icons, but I would prefer to avoid this solution anyway (using handles) :

Icon NewIcon = Icon.FromHandle(IconBitmap.GetHicon());
FileStream FS = new FileStream(Path.Combine(Target, "Icon" + Counter + ".ico"),
        FileMode.Create);
NewIcon.Save(FS);

Answer 1

It’s true that the ImageFormat.Icon does not work for writing as you’d suppose, .NET simply does not support writing .ico files and simply dumps the PNG data.

There are a few projects on CodeProject (and this one) (and another one) and that let you write an .ico file, it’s actually not that hard. The file format is pretty straight-forward, and supports BMP and PNG data.