[Algorithms] OT: How to read a bitmap of arbitrary size?

[Pai-Hung C. <pa...@ac...>]

Hi,

I have been frustratingly bugged for hours and I decide to resort to the
list.  I want to read a 24-bit bitmap heightfield.  I can correctly read it
as long as the dimension of the bitmap file is in 2's power such as 4x4,
8x8, 16x16, etc.  (But 2x2 doesn't work?!)  In these _normal_ cases, the
*biSizeImage* field of the BITMAPINFOHEADER structure gives me the correct
size of image in bytes.  However, if I create a bitmap of non-2's-power
dimension such as 5x5, 6x6, 7x7, etc., the *biSizeImage* field gives me some
bogus number.  For example, 5x5 yields 80 bytes (5x5x3 = 75 bytes); 6x6
yields 120 bytes (6x6x3 = 108 bytes); 7x7 yields 168 bytes (7x7x3 = 147
bytes).  Could somebody tell me what happened?

Thanks in advance,

Pai-Hung Chen