Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul Roark" 
<paul.roark@v...> wrote:
> Roy,
> 
>  
> > The .raw files are just saved in Photoshop RAW format.
> 
> My XP system with PS CS can save in Photoshop (*.psd); I'm not familiar with
> the "RAW" version.

It's one of the formats in Save As.

> 
> >  The files files
> > just contain the data of an image file -- no headers or formatting of
> > any kind. 
> 
> Is this something that is doable by Photoshop?

Yes, but it's a write-only format.   You don't get any info about what the
data is.  I use the file size in bytes as the only clue.
   Nchannels = Nbytes / 256pixels / 2          (2=bytes/pixel)

It's a pretty useless format unless you create it for a very specific reason.

> 
> 
> > I created 16-bit PS files that just had 256 pixels, one of
> > each possible gray value.   You can then apply a .acv curve to it and
> > save the result as a .raw.   The .raw will now contain the exact curve
> > transformation which can then be used as a component of a QTR
> > .quad file.
> 
> So, it acts as, in effect, a translation interface between the formats?

Essentially yes.  I'm using it to get the whole curve from a .acv -- including
all the smoothing between points.  Now I have some spline code that
I can do the smoothing -- only issue is that it's not identical to PS's.

> 
> Have you looked at the text file that Picture Window (an *acv-compatible
> application) allows to be edited?

No.  But the .acv's are pretty simple so making a text version wouldn't
be too hard.

> 
> >  So qacvraw takes one channel of a raw file and converts it
> > from binary to text i.e. .quad format.   You can do grayscale with one
> > channel or any number of channels 4,6,7,8 by just making the original
> > PS file and .acv N channels.
> 
> It seems to me that the conversion is one .acv curve to one .quad (?) curve.
> That sounds doable.

Yes, they (both .acv and .quad) can be multiple channels.  The qacv & qacvraw
do one channel at a time.   The .quad's are just concatenations of multiple
channels.

> 
> With the .acv curves, however, the Epson driver crossovers are in a black
> box.  Unless the conversion program contained information about the Epson
> driver cross-overs, I can not see how the program could map a .acv curve to
> the 2 QTR curves that would be needed for the, for example, C - LC
> crossover.

Your usage of RGB .acv's that will go though the Epson driver is a totally
different thing for the reasons you stated.  I'm using them for the individual
inks like K C M Y LC LM LK.  QTR has "crossover" or partitioning capability
builtin -- you just have to specify a single density to have the partitioning
done for you.

> 
> Then there is the lack of black ink crossover information.
> 
> Conversion might not be worth the work.
> 
> >  A minor issue is that PC and Mac store the
> > bytes in opposite order.   
> 
> 
> >The other program qacv extracts (x,y)
> > coordinates out of a .acv file which can be connected and smoothed.
> 
> Unless there is crossover information & algorithms, this faces the same
> problems.
> 
> I think the rips would benefit from having pre-made ink pairs that were
> based on reverse-engineered, printer-specific printer crossovers, at least
> for C-LC and M-LM.  One could put clear in alternating chambers and extract
> this information rather easily.  The Black-LK-CMY cross-over sounds like a
> bear.

Again this is all an RGB Epson driver problem, none of this is an issue if you go to
the individual inks.

Roy

> 
> Paul
> www.PaulRoark.com 
> 
> __________________________________
>  
> > 
> > --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Daniel Staver
> > <daniel@p...> wrote:
> > > The qacvraw program only works with special .RAW files that Roy created
> > > while qacv works with Photoshop .ACV curves.
> > >
> > > The qacv program will output the curve points of the first channel in a
> > > Photoshop curve as a set of x,y coordinates. Then you can use the qcurve
> > > program to transform these coordinates into 256 16bit values. These
> > > values can be used for one ink channel in QTR.
> > >
> > > In the latest, not yet released, version of QuadProfile and QTRgui we
> > > support loading a Photoshop curve for any individual ink channel. If the
> > > Photoshop curve has more than one channel the first will be used and the
> > > others discarded.
> > >
> > > If you wanted to you could create a curve for every ink channel and
> > > effectively bypass the entire profiling process in QTR and have full
> > > manual control of every ink channel. A more reasonable approach would
> > > perhaps to use this for special curves like GLOP curves where the curve
> > > for the GLOP ink might have an unusual shape and you'd want full manual
> > > control.
> > >
> > > You can also load a photoshop curve to modify a partitioned gray or
> > > toner curve. This has always been supported.
> > >
> > > In addition to this you can manually enter curve points directly into
> > > QTRgui instead of using the photoshop file format. Up to 50 curve points
> > >   are supported.
> > >
> > > This works for all printers, the only difference is the amount of ink
> > > channels you have available to work with.
> > >
> > > --
> > > Daniel Staver
> > > http://daniel.staver.no
> > >
> > > > Appendix 2 of Tom Moore's very useful Tutorial on making curves for
> > QTR
> > > > says, "quacvraw is a way to convert a photoshop curve into a
> > QuadToneRIP
> > > > curve.
> > > >
> > > > How do these work?
> > > >
> > > > What kinds of Photoshop curves are covered?
> > > >
> > > > Does it work for all Epson printers?  Hextone included?
> > 
> > 
> > 
> > 
> > 
> > 
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