[hylafax-users] Default Resolution of TIFFs

[cbain <cbain@acordex.com>]

Lee,

From TIFF 6.0 Spec Final Draft, Page 36:

ResolutionUnit
The unit of measurement for XResolution and YResolution.
Tag = 296 (128.H)
Type = SHORT
N = 1
To be used with XResolution and YResolution.
1 = No absolute unit of measurement. Used for images that may have a 
non-square
aspect ratio, but no meaningful absolute dimensions.
The drawback of ResolutionUnit=1 is that different applications will 
import the image
at different sizes. Even if the decision is arbitrary, it might be better 
to use dots per
inch or dots per centimeter, and to pick XResolution and YResolution so 
that the
aspect ratio is correct and the maximum dimension of the image is about 
four inches
(the "four" is arbitrary.)
2 = Inch.
3 = Centimeter.
Default is 2.

Chris

>Hello Chris.
>
>Your mail was greaty appreciated.  I am parsing it slowly.  My first 
>comment, though:
>
>On 2002.10.09 08:13 cbain wrote:
>
>> I discovered what I think may be a bug in "faxd/FaxSend.c++", it does
>> not
>> choose the correct default resolution unit (as per TIFF spec) if none
>> is
>> specified in the tiff file when sending. I made the following change
>> in
>> the method FaxServer::sendSetupParams1():
>> 
>> 	short resunit = RESUNIT_NONE;
>> 
>> to
>> 
>> 	short resunit = RESUNIT_INCH;
>
>http://bugzilla.remotesensing.org/show_bug.cgi?id=131
>
>Indicates that libtiff isn't following the supposed TIFF spec, either 
>then, as it also defaults to RESUNIT_NONE (PostScript units).  If a 
>change in this regard (which would impact similar code in 
>hfaxd/RecvQueue.c++, util/faxinfo.c++, util/tiffcheck.c++, as well as 
>faxd/FaxSend.c++) is warranted, then I would like to see a concerted 
>effort between HylaFAX and libtiff in getting it done.
>
>Could you provide me with the TIFF spec reference (page or section 
>number is sufficient) where this is stated?  Thanks.
>
>Lee.

____________________ HylaFAX(tm) Users Mailing List _______________________
  To subscribe/unsubscribe, click http://lists.hylafax.org/cgi-bin/lsg2.cgi
 On UNIX: mail -s unsubscribe hylafax-users-request@hylafax.org < /dev/null
  *To learn about commercial HylaFAX(tm) support, mail sales@hylafax.org.*