Wich DIB types ? Are you referring to BI_BITFIELDS compression ?
I just looked at windows codecs code and there this code to handle color masks:
/* if this is a BITMAPINFOHEADER with BI_BITFIELDS compression, we need to
read the extra fields */
if (This->bih.bV5Size == sizeof(BITMAPINFOHEADER) &&
This->bih.bV5Compression == BI_BITFIELDS)
{
This->palette_offset += 12;
}
For the rest it's the same thing:
/* In a packed DIB, the image follows the palette. */
ULONG palette_count, palette_size;
if (This->bih.bV5ClrUsed)
palette_count = This->bih.bV5ClrUsed;
else if (This->bih.bV5BitCount <= 8)
palette_count = 1 << This->bih.bV5BitCount;
else
palette_count = 0;
if (This->bih.bV5Size == sizeof(BITMAPCOREHEADER))
palette_size = sizeof(RGBTRIPLE) * palette_count;
else
palette_size = sizeof(RGBQUAD) * palette_count;
This->image_offset = This->palette_offset + palette_size;
Albeit windows codecs support also BITMAPCOREHEADER2, BITMAPV4HEADER, BITMAPV5HEADER the same way as BITMAPINFOHEADER.
Is there still anything wrong ?
Christian