[Printing-architecture] Common Printing Dialog and color management

Chris Murphy lists at colorremedies.com
Thu Feb 24 09:23:26 PST 2011


From the wiki URL provided on the CPD, I have a few concerns:

1. "Showing paper color" is fraught with peril and can totally set up the wrong end user expectations. The issue of chromatic adaptation is really not straight forward because user adaptation is unknown. They could be partially adapted, fully adapted, or not at all adapted. State of user adaptation needs to be known to do this in a way that doesn't actually hurt the user and make things worse. I definitely would not have this feature on by default. Professionals in some ways shouldn't need it because their display white should be fairly close to paper white anyway, otherwise they have even more serious adaptation issues. And last, the surrounding white point will be the display native white point, and when you have a small preview that "shows paper color" you have color appearance surround effects that really necessitate the inclusion of a color appearance model to do the simulation correctly. None of this is the case right now. So I'm not sure really why this is being included, who exactly it's going to help - what's the usage scenario.

Yes Photoshop does this in their print dialog, I don't think it's that useful, honestly. Maybe the motivation is coming from users used to Photoshop, I'm not sure.

2. There is this notion that "high end users" will want to be able to quickly turn off color management. This is confusing in the wiki. What the high end user wants is to ensure there isn't a conflict between application pre-matching content for print, and then the downstream doing additional conversions (i.e. in GhostScript/lcms). So yes, if those applications depend on pre-matching, you will need a clear mechanism for this to be disabled in the print dialog. I will warn that this area is also fraught with peril based on experiences with Mac OS and Windows. 

a. First I'd question why we even have applications that prematch data. Historically this has been because certain features weren't available downstream in the printing pipeline, like black point compensation, so we had to convert using RelCol+BPC in the application. If the printing architecture allows for RelCol+BPC, then there's no reason to clutter the workflow with color management options in the application, and color management options in the print dialog.

b. The instant you're going to have two sets of controls for color management, application and print dialog, you end up in the snare we've been in for almost 10 years on Mac OS and Windows that I would like to see not engineered again if possible. I think it's possible everyone who has put in their two cents into this color management in the CPD are simply used to this paradigm and it seems to make sense. I think it's an atrocious user experience, even for high end users. If we can do better, we should do better. Two sets of conflicting color management settings: application and print dialog is just, inane. So what Apple did was come up with a way to get the application to communicate its intent to prematch data, in an (very undocumented way, something open source doesn't tend to need to be as worried about), and thereby get the print dialog's defaults to automatically disable print pipeline color management so that there would not be this effect called "double color management." If the document is color managed twice, especially with assumptions, we end up with a mess.

So that's why I go back to a. If the print architecture is sophisticated enough, seems like if the application is going to use the CPD, that it would know that it doesn't need to prematch because it's using a new CPD that understands proper color management. And in that case does not need to present conflicting settings to the user that the user will then have to sort out; or that engineers of this system will have to compute contingencies for.

3. So I'm going to go out on a ledge and say, with not much effort, you could build a system that meets the requirements of low, mid, and high end users and consolidate the behaviors that are in the three bullet points under the chart in the wiki. I find the implied workflow in those three bullet points to be confusing, misleading, and well - basically untrue although I understand where they're coming from due to our legacy past on Windows and Mac OS. (And I am considering those legacy because those OS's have inherited some nasty baggage for various reasons).

4. "Soft proof" I wish we could remove this term from our lexicon. This is a very high end feature that is really difficult to achieve even for very high end users. It requires an extremely standardized environment, or it requires the use of advanced color appearance models. I have no issue with ensuring that it can be implemented into user's workflows, but the idea that "mid end users" will be using a CPD preview to soft proof is a lunacy asylum. It's not going to help them one little bit and it adds unnecessary engineering that will not work at all. Maybe the original idea behind this is "fake soft proofing" versus "real soft proofing" but when I use the term soft proofing I am thinking of an event where there is a very close similarity between print and preview. This is very difficult to arrive at for most users because they're in non-standard viewing conditions, and simply the quantity of light available can make the different between "spot on" and "ew that's a dark print". It's not subtle.

5. I think the CPD probably needs to interface with colord, to present one of four possibilities for the destination profile (the printer profile), in order of priority:
	a.) A custom profile chosen by the user, directly in the CPD.
	b.) An indication that the application is going to prematch data. I realize I'm arguing against this is in 2a above, but if it's going to be an enabled workflow anyway, then the CPD should inform the user that the application is set to prematch data, not require them to choose such a "set by application" option. I'm not sure if there is a role here for colord to get this info from the app, or if the app talks to the CPD directly. Probably the later.
	c.) The profile for the printing condition based on *cupsICCProfile which I think colord is going to be aware of, so in this case colord forwards this setting to the CPD.
	d.) The profile for the printing condition based on *cupsICCProfile not being present in (legacy) PPDs. We need to assume something, what's it going to be? This is probably sRGB for any desktop inkjet printer, and might even work for quite a few color laser printers, which can receive both RGB and CMYK data. If the printer is CMYK only and you don't have *cupsICCProfile in the PPD and you don't have a user selection - well you're basically screwed but you have to pick something, or fail the job. And almost no matter what you pick for CMYK it will be wrong. So we probably need some really conservative CMYK space to use that is probably a separate discussion.

So at the very least, in c. colord needs to integrate with the CPD and let it know what that *cupsICCProfile is. And in the case of d.) we might want colord forward a user chosen default to the CPD, so the user doesn't have to keep choosing something sensible, if the default colord has in mind is not ideal.

6. "Using the preview" section of the wiki. 

a.  On the one hand the wiki says "This is an essential part of describing and showing exactly what a user is getting" and then proceeds to show a mockup of the print dialog where "auto assign" and "automatic" are used for ICC color profile and Rendering intent. This is confusing because automatic is just another word for random. It's definitely not describing anything exact. There is a cascading set of fallback for an automatic population of this dialog, but it should show exactly what is going to be used. Auto is not exact.

b.  Also, the term "ICC color profile" is vague. What's this profile referring to? Is it a source profile? Is it an intermediate profile? Is it a destination profile? It should be specific. Maybe it should say "Printer profile".


7. I think having "ICC color profile" and "rendering intent" in two different parts of the print dialog is confusing. Pick one area, stick with it.


I think that's all I have at the moment.

Chris



On Feb 24, 2011, at 8:36 AM, peter sikking wrote:

> Richard Hughes wrote:
> 
>> I've been doing quite a lot of research in to the Common Printing
>> Dialog in the last two days for my colord integration. I'm really not
>> sure where it fits in my color managed architecture plans.
>> 
>> From my perhaps-naïve point of view, CPD seems to have 3 main problems:
>> 
>> * There hasn't been any code merged in 5 *years*, even though quite a
>> lot of code has already been written.
>> * Neither GTK or KDE seem to want to include a new UI that doesn't
>> match either of their HIG guidelines.
> 
> both KDE and GNOME will happily take the patches. there is a lot of
> enthusiasm for it at both platforms. just not to do the work. so we
> have to get it to work as a large infrastructure project, then it
> can go in.
> 
> about the HIG: in the spec you are looking at is a KDE/GNOME agnostic
> meta spec, the implementation is done for KDE and GNOME separately,
> fully HIG-compliant.
> 
>> * Every single PPD file on the planet would need to be modified to
>> support the CPD.
> 
> Till has ensured that the cpd is backward compatible with any
> (decent) PPD file on the planet. apart from that all major
> printer manufacturers have been planning and gearing up for
> PPD amending that will unlock the full cpd potential.
> 
>> So basically, I'm not sure what the CPD buys us. Looking at
>> http://wiki.openusability.org/wiki/printing/index.php/Photo_printers_parameter_specifications#Color_Management_and_the_CPD
>> I'm not convinced mixing the color management settings in with the
>> printing options makes a lot of sense either.
> 
> 
> now it is getting interesting.
> 
> I am not sure what you mean exactly. please be a bit more
> precise about what you do not see working, from which perspective
> (technical, color workflows, or something else).
> 
>    --ps
> 
>        founder + principal interaction architect
>            man + machine interface works
> 
>        http://blog.mmiworks.net: on interaction architecture
> 
> 
> 
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