lgm talk, part 1...

[peter sikking]

guys,

just to let you know that I have blogged the first part of my
lgm talk, read all about it at:

<http://www.mmiworks.net/eng/publications/2009/05/gimp-enter.html>

enjoy,

     --ps

         founder + principal interaction architect
             man + machine interface works

         http://mmiworks.net/blog : on interaction architecture



_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[peter sikking]

guys,

the second part of my lgm talk is blogged now:

<http://www.mmiworks.net/eng/publications/2009/06/gimp-squaring-cmyk-circle.html 
 >

enjoy,

     --ps

         founder + principal interaction architect
             man + machine interface works

         http://mmiworks.net/blog : on interaction architecture



_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[yahvuu]

Hi all,

there's one thing i don't understand, may be a misconception:
why is it necessary to have separate modes for editing the RGB data
and the plates?

For example, if i have an RGB image in the composition and want to apply
'value curves', that has to be done in the RGB area, for after
separation the plates are treated individually.
Now only after manually pulling over the 'press projection' again i
can discover that this operation
drove my plates out of gamut.

Is it correct that there's no 'live preview' of the effects that RGB
manipulations have on the plates?


greetings,
peter
_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[peter sikking]

(peter) yahvuu wrote:

> there's one thing i don't understand, may be a misconception:
> why is it necessary to have separate modes for editing the RGB data
> and the plates?

mainly because creating art on a RGB monitor, to be used on
many media, is not the same _activity_ as bringing this art to
_one_ particular printing press.

also, it is better when the art itself is separated from the  
adaptation of
it for one press run.

> For example, if i have an RGB image in the composition and want to  
> apply
> 'value curves', that has to be done in the RGB area, for after
> separation the plates are treated individually.

the question is what is the curve for? is it artistic? then RGB is your
space. getting the plates right? then chain them together and do a  
curve.

> Now only after manually pulling over the 'press projection' again i
> can discover that this operation drove my plates out of gamut.

there is going to be no substitute for experience with printing presses
and especially the particular press one is working towards.

> Is it correct that there's no 'live preview' of the effects that RGB
> manipulations have on the plates?


if that is really needed by some users (see the two activities above
and also "no substitute for experience") then a second view of the
file (View->New view) can be run with the projection pulled down.
might be hard on the processor.

     --ps

         founder + principal interaction architect
             man + machine interface works

         http://mmiworks.net/blog : on interaction architecture



_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[Alexandre Prokoudine]

On Fri, Jun 19, 2009 at 8:05 PM, yahvuu wrote:

> there's one thing i don't understand, may be a misconception:
> why is it necessary to have separate modes for editing the RGB data
> and the plates?
>
> For example, if i have an RGB image in the composition and want to apply
> 'value curves', that has to be done in the RGB area

In 21st century there are no RGB curves :) There are LAB and L*c*h* ones ;)

Alexandre
_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[Chris Mohler]

On Fri, Jun 19, 2009 at 10:37 AM, peter sikking<peter@...> wrote:
> guys,
>
> the second part of my lgm talk is blogged now:
>
> <http://www.mmiworks.net/eng/publications/2009/06/gimp-squaring-cmyk-circle.html

I like this approach.

I have a few questions:

Will each plate have a density or opacity attribute?  (some inks are
more opaque than others)

Will it be possible to edit an individual plate in grayscale?

And finally, will it be possible to perform operations on the RGB
portion of the image that do not take (immediate) effect on the
projection?  For example, if I want to go back and add a portion of my
RGB artwork to a plate, I might want to clone and existing RGB layer,
perform some modifications, then apply the contents of that new layer
to one of the plates.

Thanks,
Chris
_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[peter sikking]

Chris Mohler wrote:

>> <http://www.mmiworks.net/eng/publications/2009/06/gimp-squaring-cmyk-circle.html
>
> I like this approach.
>
> I have a few questions:
>
> Will each plate have a density or opacity attribute?  (some inks are
> more opaque than others)

I guess that the complexities of ink simulation start showing here.

> Will it be possible to edit an individual plate in grayscale?

well, as pippin said: the individual plates _are_ grayscale/monochrome
drawables. they will be editable just like layer masks or selections.

> And finally, will it be possible to perform operations on the RGB
> portion of the image that do not take (immediate) effect on the
> projection?  For example, if I want to go back and add a portion of my
> RGB artwork to a plate, I might want to clone and existing RGB layer,
> perform some modifications, then apply the contents of that new layer
> to one of the plates.


I am curious why you want to do something like that, because you
are then going against the grain of the whole plan: freedom to develop
the artistic concept further without (much) rework on the plates.

     --ps

         founder + principal interaction architect
             man + machine interface works

         http://mmiworks.net/blog : on interaction architecture



_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[Øyvind Kolås]

On Fri, Jun 19, 2009 at 6:56 PM, Alexandre
Prokoudine<alexandre.prokoudine@...> wrote:

> On Fri, Jun 19, 2009 at 8:05 PM, yahvuu wrote:
>
>> there's one thing i don't understand, may be a misconception:
>> why is it necessary to have separate modes for editing the RGB data
>> and the plates?
>>
>> For example, if i have an RGB image in the composition and want to apply
>> 'value curves', that has to be done in the RGB area
>
> In 21st century there are no RGB curves :) There are LAB and L*c*h* ones ;)

Not that the difference really matter as both linear light RGB and CIE
Lab are fully mutually transformable into each other. For CIE Lab or
Lch it would only make proper sense to control the L, other controls
can be used for tuning white point etc in those color models though.

/Øyvind K.
--
«The future is already here. It's just not very evenly distributed»
                                                 -- William Gibson
http://pippin.gimp.org/                            http://ffii.org/
_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[Chris Mohler]

On Fri, Jun 19, 2009 at 12:41 PM, peter sikking<peter@...> wrote:

> Chris Mohler wrote:
>
>>>
>>> <http://www.mmiworks.net/eng/publications/2009/06/gimp-squaring-cmyk-circle.html
>>
>> I like this approach.
>>
>> I have a few questions:
>>
>> Will each plate have a density or opacity attribute?  (some inks are
>> more opaque than others)
>
> I guess that the complexities of ink simulation start showing here.

Yes - although transparency/opacity would be enough for me to use GIMP
for professional separation work.  I'm reasonably sure that PS uses a
variant of the blending mode Multiply for spot channels, and this
works fairly well.

>> Will it be possible to edit an individual plate in grayscale?
>
> well, as pippin said: the individual plates _are_ grayscale/monochrome
> drawables. they will be editable just like layer masks or selections.

Excellent.

>> And finally, will it be possible to perform operations on the RGB
>> portion of the image that do not take (immediate) effect on the
>> projection?  For example, if I want to go back and add a portion of my
>> RGB artwork to a plate, I might want to clone and existing RGB layer,
>> perform some modifications, then apply the contents of that new layer
>> to one of the plates.
>
>
> I am curious why you want to do something like that, because you
> are then going against the grain of the whole plan: freedom to develop
> the artistic concept further without (much) rework on the plates.

Imagine I'm designing a black t-shirt with say five spot colors,
including white.  After completing the artistic design, I enable the
'projection screen'.  This theoretically would result in my five
"plates".  However, the white plate will need special attention.

Here's my workflow for this in PS: I would use the (badly named)
'Apply Image' command to take the contents of each color plate and
combine them into the white plate using the mode 'multiply'.  I would
also manually "choke" the white plate - this means making the white
areas a point or two smaller than the colored areas, thereby
preventing the white from poking out at the edges of the colored
areas.  This process can get a bit tricky, especially if the original
artwork is very complex.  Often, create temporary layers (or plates),
perform selection/drawing functions, then combine the result back into
a plate in one of two ways - either making a selection on the temp
layer and going to the plate and filling or erasing, or using the
'Apply Image' command to take the RGB channel of the current layer and
combine it with a plate using a mode such as Multiply, Screen, or Add.

Now, I am quite interested in learning new workflows - so I am not
bound to the "how" of the method above, but I hope I have explained
the "why" well enough.  In addition to being able to interact with
each plate as a grayscale drawable, it would be useful to create
temporary areas for doing work - be they layers, channels, plates,
whatever - on which to create paths, selections, etc to in turn use to
modify the plates manually.  Icing on the cake would be a mechanism to
combine/subtract plates using the available blending modes.  During
the process, it is fairly critical to have an ink density/opacity
setting for each plate, to simulate (roughly) how the final print is
going to look.  EG, set the white plate at approx 90%, the colors at
approx 70% - and you can see which portions of the colors are falling
on the white underlay, and which portions are falling on the black
shirt.

I realize that this is just one corner case, but if you visualize each
plate being printed separately, in order, you may be able to recognize
some of the many 'gotchas' inherent in separating the artistic artwork
into something suitable to send to the press.  That's why (in my
opinion) it is important to have as much control as possible over each
plate.

Whew ;)

If I explained any of this poorly, I am sorry and will happily try to do better.

All in all, I am very pleased with the direction that this is taking
and I would certainly like to use GIMP for even more of my production
work. :)

Thanks,
Chris
_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[Andrew A. Gill]

On Fri, 19 Jun 2009, peter sikking wrote:

> guys,
>
> the second part of my lgm talk is blogged now:
>
> <http://www.mmiworks.net/eng/publications/2009/06/gimp-squaring-cmyk-circle.html
> >
>
> enjoy,

I do appreciate your work on this, but I have to say that I still
have some concerns.

I have to go somewhere, so I haven't read evreything
yet, but I'd like to make this point.  Converting from CMYK to
RGB and vice versa are not lossless by a long shot.  This is by
necessity and the fact that GEGL is non-destructive has nothing
to do with it, since large porions of image data will have to be
tossed when converting.

The gamut for RGB is far larger in the bright colors, and CMYK
can produce effects that cannot be produced in RGB.

See, for example:
<http://arstechnica.com/gadgets/news/2009/06/expanding-the-gamut-sharp-to-increase-color-range-of-lcds.ars>

I am very concerned that your overlay concept would simply
degrade the image over successive conversions.

--
| Andrew A. Gill     To ensure continued quality of service,   |
|                    this e-mail is being monitored by the NSA |
| <superluser@...> <http://www.needsfoodbadly.com> |
                                                               --
_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[Martin Nordholts-2]

Andrew A. Gill wrote:

> On Fri, 19 Jun 2009, peter sikking wrote:
>  
>> guys,
>>
>> the second part of my lgm talk is blogged now:
>>
>> <http://www.mmiworks.net/eng/publications/2009/06/gimp-squaring-cmyk-circle.html
>>    
>> enjoy,
>>    
>
> I have to go somewhere, so I haven't read evreything
> yet, but I'd like to make this point.  Converting from CMYK to
> RGB and vice versa are not lossless by a long shot.  This is by
> necessity and the fact that GEGL is non-destructive has nothing
> to do with it

Isn't it a good idea to first read what you are commenting on?

It seems to me you completely misunderstood the whole thing. What makes
you think there is any CMYK -> RGB conversion involved here?

 / Martin
_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[yahvuu]

hi,

peter sikking schrieb:

> (peter) yahvuu wrote:
>
>> there's one thing i don't understand, may be a misconception:
>> why is it necessary to have separate modes for editing the RGB data
>> and the plates?
>
> mainly because creating art on a RGB monitor, to be used on
> many media, is not the same _activity_ as bringing this art to
> _one_ particular printing press.
>
> also, it is better when the art itself is separated from the adaptation of
> it for one press run.

ah, that helps. So it is deprecated to create single-ink 'light blue text'
directly on  the 'light blue' plate, as the text would then not be known to
be part of the artwork.

Can you give an outline how the print color for that text will be specified?
The RGB color isn't useful here and the text layer can't be accessed while
the press projection is pulled over, IIUC. So each artwork layer will have
a custom color separation setting resp. color mapping?

>> For example, if i have an RGB image in the composition and want to apply
>> 'value curves', that has to be done in the RGB area, for after
>> separation the plates are treated individually.
>
> the question is what is the curve for? is it artistic? then RGB is your
> space. getting the plates right? then chain them together and do a curve.
>
>> Now only after manually pulling over the 'press projection' again i
>> can discover that this operation drove my plates out of gamut.
>
> there is going to be no substitute for experience with printing presses
> and especially the particular press one is working towards.

sure. Gamut warnings can only ease the first step, by guiding
the color separation process.



>> Is it correct that there's no 'live preview' of the effects that RGB
>> manipulations have on the plates?
>
>
> if that is really needed by some users (see the two activities above
> and also "no substitute for experience") then a second view of the
> file (View->New view) can be run with the projection pulled down.
> might be hard on the processor.

Regarding the use-case of matching one color from a photo with a
predetermined ink combination, i think this will be useful.


greetings,
peter

_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[yahvuu]

hi,

Chris Mohler schrieb:
> Imagine I'm designing a black t-shirt with say five spot colors,
> including white.
[..]
> Whew ;)

Whew, too ;) Makes me wonder if it has to be that hard or if
it points to some missing software improvements. Trying to understand
the example, i hope you don't mind some uninformed questions (and also
some out-of-sequence quoting).

Besides anticipating printing press idiosyncrasies ('choke'),
it seems to me you're manually creating kind of a color separation.
Quite naively: doesn't photoshop know you're printing on black?


> Here's my workflow for this in PS: I would use the (badly named)
> 'Apply Image' command to take the contents of each color plate and
> combine them into the white plate using the mode 'multiply'.  

this is to create the white underpinning, resp. the beginning thereof.
'Apply Image' is short-hand for 'blend anything with anything',
but doesn't do any tricks that could not be achieved with layer stacks
in combination with proper channel masking. On track?


> I would
> also manually "choke" the white plate - this means making the white
> areas a point or two smaller than the colored areas, thereby
> preventing the white from poking out at the edges of the colored
> areas.  This process can get a bit tricky, especially if the original
> artwork is very complex.

if the artwork was fully vectorized, say a pure inkscape job,
would that make things easier?


> Often, create temporary layers (or plates),
> perform selection/drawing functions, then combine the result back into
> a plate in one of two ways - either making a selection on the temp
> layer and going to the plate and filling or erasing, or using the
> 'Apply Image' command to take the RGB channel of the current layer and
> combine it with a plate using a mode such as Multiply, Screen, or Add.

i assume the temporary layers are mostly grayscale?

the temporary layers serve as 'mixing stage' because it takes
several steps to create a desired mask, or is it more
to keep selections/drawings for reuse?


thanks for your patience,
peter




_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

Hello Martin!

On Saturday 20 June 2009, Martin Nordholts wrote:
> It seems to me you completely misunderstood the whole thing. What makes
> you think there is any CMYK -> RGB conversion involved here?
>
>  / Martin

I think Andrew referred to this part from Peter's article:
> what about CMYK files?
>
> When a received CMYK file is to be used in new creative work, we already
> saw that ‘it needs to be imported and converted to RGB.’

Daniel


_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

Sorry, I just saw that Guillermo cleared up that misunderstanding already.
(Though it was not detected as part of the same thread by my mail client.)

Daniel


_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[yahvuu]

hi,

Tobias Ellinghaus schrieb:

> Am Samstag, 20. Juni 2009 schrieb yahvuu:
>
> [...]
>
>> Can you give an outline how the print color for that text will be
>> specified? The RGB color isn't useful here and the text layer can't be
>> accessed while the press projection is pulled over, IIUC. So each artwork
>> layer will have a custom color separation setting resp. color mapping?
>
> From Peter's blog post:
>
> "However there will be full flexibility to map the content of any layer
> directly to any plate. For instance that light blue text in our example: it
> can be directly mapped from its text layer to the light blue plate, bypassing
> the composite."
>
>
> I understand that you can use layers as plates.

yep, that's the desired effect here. For the single-ink text example, a bit more
than filling the light blue plate to 100% is required, though, as the other
plates have to be set to 0% for that area.

My question is how and where such a layer->plate mapping will be specified,
for example when i want my text to be (0, 0, 50%, 50% ,0) on the five plates.


greetings,
peter

_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[Chris Mohler]

On Sat, Jun 20, 2009 at 11:27 AM, yahvuu<yahvuu@...> wrote:

> hi,
>
> Chris Mohler schrieb:
>> Imagine I'm designing a black t-shirt with say five spot colors,
>> including white.
> [..]
>> Whew ;)
>
> Whew, too ;) Makes me wonder if it has to be that hard or if
> it points to some missing software improvements. Trying to understand
> the example, i hope you don't mind some uninformed questions (and also
> some out-of-sequence quoting).
>
> Besides anticipating printing press idiosyncrasies ('choke'),
> it seems to me you're manually creating kind of a color separation.
> Quite naively: doesn't photoshop know you're printing on black?

Yes - I end up doing a lot of it manually, and no it does not know -
having a 'target' or 'base' would be a step forward.

>> Here's my workflow for this in PS: I would use the (badly named)
>> 'Apply Image' command to take the contents of each color plate and
>> combine them into the white plate using the mode 'multiply'.
>
> this is to create the white underpinning, resp. the beginning thereof.
> 'Apply Image' is short-hand for 'blend anything with anything',
> but doesn't do any tricks that could not be achieved with layer stacks
> in combination with proper channel masking. On track?

Yes.

>
>> I would
>> also manually "choke" the white plate - this means making the white
>> areas a point or two smaller than the colored areas, thereby
>> preventing the white from poking out at the edges of the colored
>> areas.  This process can get a bit tricky, especially if the original
>> artwork is very complex.
>
> if the artwork was fully vectorized, say a pure inkscape job,
> would that make things easier?

Of course, but when photographic-type artwork comes into play, it's
usually easier/faster to do the whole thing in a raster editor.

>
>> Often, create temporary layers (or plates),
>> perform selection/drawing functions, then combine the result back into
>> a plate in one of two ways - either making a selection on the temp
>> layer and going to the plate and filling or erasing, or using the
>> 'Apply Image' command to take the RGB channel of the current layer and
>> combine it with a plate using a mode such as Multiply, Screen, or Add.
>
> i assume the temporary layers are mostly grayscale?

Usually RGB layers, or grayscale channels.

> the temporary layers serve as 'mixing stage' because it takes
> several steps to create a desired mask, or is it more
> to keep selections/drawings for reuse?

A little of both.  Sometimes I just need a very complex selection, but
I need to do some work to create the selection.  Other times I need to
store a selection for later use  (that's generally when I make an
extra channel).


After re-reading the notes on the talk, if we have a Layer->Plate
mapping, I think that will cover most situations.  I would prefer a
way to "mix" the plates, and to be able to add new layers that could
later be applied to new or existing plates, but this could be worked
around.

Chris
_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[yahvuu]

hi,

Chris Mohler schrieb:
> On Sat, Jun 20, 2009 at 11:27 AM, yahvuu<yahvuu@...> wrote:
>> i assume the temporary layers are mostly grayscale?
>
> Usually RGB layers, or grayscale channels.

sorry, imprecise question. I mean, if you use a temporary RGB layer,
it's content will still usually be just grayscale, effectively used
as a mask. Assumed correctly?


greetings,
peter

_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[Chris Mohler]

On Sat, Jun 20, 2009 at 12:07 PM, yahvuu<yahvuu@...> wrote:

> hi,
>
> Chris Mohler schrieb:
>> On Sat, Jun 20, 2009 at 11:27 AM, yahvuu<yahvuu@...> wrote:
>>> i assume the temporary layers are mostly grayscale?
>>
>> Usually RGB layers, or grayscale channels.
>
> sorry, imprecise question. I mean, if you use a temporary RGB layer,
> it's content will still usually be just grayscale, effectively used
> as a mask. Assumed correctly?

Not necessarily - consider another scenario: mixing two spot colors to
create a third color.  More accurately, consider an image (RGB) that
is primarily three colors, and then attempting to print that image in
two colors, getting as close to the original RGB artwork as possible
(the number of spot colors is a major factor in printing cost).

In that scenario, I may end up duplicating the original RGB artwork
several times before getting the selection that I want - then
ultimately filling or erasing that selection on the spot channel(s).
The process can be very non-intuitive at times, and sometimes you just
have to dive in and do some trial and error - esp. if the original RGB
image is something flat that was not originally intended to be printed
in such a way or is "damaged" (eg, not on layers, suffers from JPEG
compression, etc.).

Chris
_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

[Hal V. Engel]

On Saturday 20 June 2009 09:40:22 am Daniel Hornung wrote:

> Hello Martin!
>
> On Saturday 20 June 2009, Martin Nordholts wrote:
> > It seems to me you completely misunderstood the whole thing. What makes
> > you think there is any CMYK -> RGB conversion involved here?
> >
> >  / Martin
>
> I think Andrew referred to this part from Peter's article:
> > what about CMYK files?
> >
> > When a received CMYK file is to be used in new creative work, we already
> > saw that ‘it needs to be imported and converted to RGB.’

And I am not sure that this is the correct approach.  Why would this be
needed?  Is this so that we can deal with GIMPs limited functionality to
handle anything beyond RGB color spaces?  If so then the focus should be on
supporting other color spaces directly.  

I also have not any anything in the thread related to how color management
fits.   After all how do you create the printer specific separations from an
RGB (or other non-device specific) image into the correct device values
without involving the color management engine?

Hal
_______________________________________________
Gimp-developer mailing list
Gimp-developer@...
https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer