Re: Turn off color management!
Re: Turn off color management!
- Subject: Re: Turn off color management!
- From: edward taffel <email@hidden>
- Date: Wed, 09 Mar 2016 11:47:56 -0500
- Sun-java-system-smtp-warning: Lines longer than SMTP allows found and wrapped.
i believe the concept of colorsync on/off is causing some confusion: colorsync is always on in quartz; as mentioned previously, if the CGImage api is used to read an untagged raster a default profile is assigned, e.g. ‘srgb’ for an rgb model, ‘generic cmyk’ for cmyk. a programmer must set a flag to remember that a raster is untagged & be prepared to handle a do-not-manage workflow, if desired.
an emitter, whether streaming to a rip or a file, formats an operation that determines what occurs in the rip. [have a look at the image operator entry in a pdf or postscript reference for some clarity.]
so, a possible operational-semantics for these settings might be [we need the source to be sure]:
prematch: use the colorsync api to perform a conversion to the destination, & format the image with the destination or none. [tagged with destination should evoke, to my way of thinking, what constitutes a null transform, e.g. if(source = dest) no_op.]
hand off: let the printer’s rip handle the conversion
print as color target: i assume we just want coordinates here [yes?]. the emitter ignores the profile (does not use the colorsync api to setup a conversion) & formats the image untagged—no in-rip conversion ensues. [i’m not 100% sure of my take on this: the emitter may apply ’some’ mapping, but this is the general idea—perhaps someone can add clarity.]
> On Mar 9, 2016, at 4:39 AM, Uli Zappe <email@hidden> wrote:
>
> Am 08.03.2016 um 23:48 schrieb Graeme Gill <email@hidden>:
>
>> The point of the null transform is to use the normal printing path, not one that attempts to turn off color management like the ColorSync or Adobe utility (if that's actually what they are doing.)
>
> No, ColorSync Utility at least does not do it this way. It makes sure that no color management takes place by turning *on* ColorSync. Because this means ColorSync has full control (*if* the printer driver is written according to Apple’s guidelines) and thus can prevent any color transformation from happening.
>
> You can easily verify this in the Print dialog in ColorSync Utility: If you set the Color: popup in the ColorSync Utility pane to one of its three values and then go to the Color Matching pane, you will find the ColorSync – <No ColorSync> radio buttons updated accordingly, so you’ll see what each of the ColorSync Utility > Colors: values does.
>
> Which is:
>
> Prematch to printer profile: ColorSync is ON
> Hand off to printer: ColorSync is OFF
> Print as color target: ColorSync is ON
>
> BTW, "Hand off to printer" means exactly that. It does *not* mean "No Color Management at all" – as is it is often paraphrased outside the context of ColorSync Utility –, but "Let the printer driver do with colors whatever it wants to do (which might be nothing, or might be some fancy color processing, depending on the specific driver and the user settings it offers in the vendor specific panes of the Print dialog).
>
> *But* according to Apple’s guidelines, the printer driver *must not* perform *any* color processing on its own as soon as ColorSync is turned *on* in the Print dialog > Color Matching pane. It seems that the old Canon printer drivers ignored this.
>
>
> Bye
> Uli
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>
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