[Openicc] cups-filters

[Robert Krawitz]

On Fri, 16 May 2014 13:51:12 -0700, Michael Sweet wrote:
> Till,
>
> Gutenprint offers a 16-bit mode...

Yep.  It's fully supported, and we do test both 8 and 16 bit input.

> On May 16, 2014, at 1:39 PM, Till Kamppeter <till.kamppeter at gmail.com> wrote:
>
>> On 05/15/2014 08:39 PM, James Cloos wrote:
>>> TK> Also 16 bit color depth with Black and RGB gives broken output.
>>> 
>>> Might there be an endian issue?  PDF is big-endian.  The raster file's
>>> endianness is specified by its 1st 32 bits, 't','S','a','R' for little-
>>> or 'R','a','S','t' for big-endian.  (The pwg raster spec seems to have
>>> lost mention of that; the cups raster spec retains that detail.)
>> 
>> I have done more investigations on 16-bit Raster files and swapping each
>> pair of two bytes in the bitmap (switching endianess) makes the PDF
>> coming out correctly. This means something is Little Endian here, either
>> Ghostscript's PWG Raster output (I have fixed Ghostscript to use the
>> correct cupsRasterOpen so that I get "Ras2" files), or there is an
>> Enidan switching somewhere in QPDF (CCing Jay from QPDF).
>> 
>> As there is no consumer of 16-bit Raster (printer drivers usually take
>> 8-bit or 1-bit per color) there was not much testing whether the
>> renderers (Poppler, Ghostscript) produce correct 16-bit CUPS/PWG Raster
>> output. So it is perhaps possible that the output is Little Endian and
>> not Big Endian as it should.
>> 
>> Note also that I could only test with Ghostscript output, as I did not
>> yet succeed to make the Poppler-based pdftoraster produce PWG Raster output.
-- 
Robert Krawitz                                     <rlk at alum.mit.edu>

MIT VI-3 1987 - Congrats MIT Engineers 6 straight men's hoops tourney
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