Windows 1.0 Icon
The Windows 1.x variant of the ICO format is used in Microsoft Windows versions 1 and 2 to define monochrome icons. It has little in common with the ICO format used by Windows 3 and above.
Format
Files begin with a little-endian word, which is one of:
| Value | Meaning |
|---|---|
| 0001 | Device-Independent Format |
| 0101 | Device-Dependent Format |
| 0201 | Both formats |
This is followed by a 12-byte header describing the icon bitmap:
| Offset | Type | Meaning |
|---|---|---|
| 0000 | DWORD | Not used (corresponds to hot spot X/Y in the Windows_1.0_Cursor format). |
| 0004 | WORD | Width of bitmap in pixels |
| 0006 | WORD | Height of bitmap in pixels |
| 0008 | WORD | Width of bitmap in bytes |
| 000A | WORD | Not used (corresponds to cursor color in the Windows_1.0_Cursor format). |
Two bitmaps come after the header, each csHeight * csWidthBytes bytes long. The first bitmap is ANDed with the screen pattern; then the second is XORed on top of it.
A file in 'device independent' format is stored at double its eventual size (so a 32×32 icon would be saved as a 64×64 bitmap). A file in 'Both formats' format contains the header and bitmaps for the 'device-independent' version of the bitmap, followed by the header and bitmaps for the 'device-dependent' version.
See also
Sample files
- Samples can be found in the Windows 2.x DDK, or generated with the Windows 1.x / 2.x icon editor ICONEDIT.
