Converting ICO to BMP

I want to read ICO file and save every icon into separate BMP. My code does the trick for the first icon in ICO files. But then I don't know where to set the file cursor (where to fseek to).

Here's are the steps I do, in pseudocode:

1. Read ICONDIR = read first 6 bytes:
   
   
   
   • UInt16 as 'reserved' (always 0)
   
   
   • Uint16 as 'type' (1 for ICO, 0 for CUR)
   
   
   • Uint16 as 'count' (number of icons)
   
   
   
   


2. Read ICONDIRENTRY = next 16 bytes
   
   
   
   • Uint8 as 'width'
   
   
   • Uint8 as 'height'
   
   
   • Uint8 as 'colors'
   
   
   • Uint16 as 'color planes'
   
   
   • Uint16 as 'bits per pixel'
   
   
   • Uint32 as 'size of image'
   
   
   • Uint32 as 'offset'
   
   
   
   


3. Set the file position to the 'offset'. Read BITMAPINFOHEADER = next 40 bytes
   
   
   
   • Uint32 as 'header size'
   
   
   • Uint32 as 'width2'
   
   
   • Uint32 as 'height2'
   
   
   • Uint16 as 'color planes2'
   
   
   • Uint16 as 'bits per pixel2'
   
   
   • Uint32 as 'compression'
   
   
   • Uint32 as 'image length'
   
   
   • Uint32 as 'dpi X'
   
   
   • Uint32 as 'dpi Y'
   
   
   • Uint32 as 'colors used'
   
   
   • Uint32 as 'important colors'
   
   
   
   


4. Read the pixels of the image, from offset = 40 + 'offset' I read 'width' * 'height' * 'bits per pixel' / 8 bytes. And I got first icon from ICO files. So far so good.

But where do I fseek to now? I tried reading from the place I finished but with no luck. I know the next icon is 48x48 bytes in size, so I think i should read next ICONDIRENTRY which should give me 'width' and 'height' = 48. But I don't know where to start reading from.

I am writing the program in PHP but PHP guys for questions like this usually say 'use library X' or 'use ImageMagick' and I just need to know the algorithm. Such programs are usually written in C++ so I tagged this C++.

Where is the next ICONDIRENTRY in the ICO file (what offset)?