BITMAPINFOHEADER biHeight is twice as much as I expect

Question

I am writing a C application for parsing Windows icon files (ICO).

When I read an existing icon entry in the BITMAPINFOHEADER structure, all the variables in the structure contain the expected values, except that biHeight , which should contain the height in pixels of the image, is always twice what it should be.

So for example, if I have a 64x64 icon, biWidth is 64, but biHeight is 128.

Is this the expected behavior? This is my first time when it comes to BITMAPINFOHEADER .

I mainly work from an article

Answer 1

Yes, it is normal. This is the added height of the “AND” bitmap mask and the “XOR” bitmap, so for any normal icon it's just 2X the height of the icon. (These masks are no longer used for 32-bit icons, they are a delay.) Just split into two.