LibTiff Mailing List

TIFF and LibTiff Mailing List Archive
January 1997

Previous Thread
Next Thread

Previous by Thread
Next by Thread

Previous by Date
Next by Date

The TIFF Mailing List Homepage
This list is run by Frank Warmerdam
Archive maintained by AWare Systems

1997.01.15 19:57 "Format for different bits_per_sample", by Ken Land

Hi,

I've been using libtiff for cross platform B&W images since ~1991.

Now (finally) I'm adding support in my apps for all image formats.

I'm a bit confused on how pixel samples are encoded into the
user buffer by TIFFReadScanline() for different bits_per_sample
values.  I know that 1 bps packs 8 pixels into each byte.
I assume that 2 bps packs 4 into each byte, but what about
3 bps?  Does it pack 3.66 pixels into each byte? or does
it waste the extra two bits?

The docs aren't real clear but seem to indicate that all bits
in the buffer are used which isn't a big deal but makes building
the cross platform masks a bit more interesting.

Oh yeah, while I'm at it - are there any funnies (exceptions)
for 4,5,6,or 7 bps? (pallette?, RGB?, Grey?)

What about 12 or 16 bps images?  Others I should know about?

Thanks,

Ken Land
kland@neuralog.com