[argyllcms] Re: xsane color management


On Sunday 01 June 2008 05:10:14 Geert Janssens wrote:
> Hi,
>
> The purpose of this message is twofold:
>
> 1. Firstly, it is meant as a heads up for other people on this list: as of
> version 0.993 xsane has integrated colormanagement. I'd use the latest
> version 0.995 though as there were some issues in the releases inbetween.
> xsane uses little cms for the necessary transforms.
> To use color management with xsane, these configuration parameters are
> available:
> * use black level compensation or not, together with rendering intent
> * an RGB input profile for the scanner
> * a grayscale input profile for the scanner
> * an RGB display profile
> * a proofing profile (beyond my scope currently as I haven't learned about
> proofing yet :-) )
> * a workingspace profile. If omitted, sRGB is used by default
>
> I have set the RGB input profile and the display profile. After enabling
> colormanagement, the colors in the preview window shifted, so it seems the
> transforms are working.
>
> For each scan you make, you can choose whether to:
> * store the original scanned values together with the scanner profile
> * convert the input to sRGB and save without profile
> * convert to your preferred working space and save it as such with the
> working space profile.
>
> It all looks very simple and functional to my inexperienced eye.
>
> 2. Secondly, I have come across a small annoyance in xsane with respect to
> color management.
> I don't have a grayscale ICC profile, so I didn't bother entering it. As
> long as I only make color scans I don't really need it anyway.
>
> But after my experiments, I restarted xsane and I got this error:
>
> Error during CMS conversion:
> Could not create transform
>
> When started from the commandline, the above error is accompanied by this
> line in the terminal:
> lcms: Error #12288; Input profile is operating on wrong colorspace.
>
> Apart from this, everything seems to work fine. It took me a while before I
> discovered this is the exact same error message I get if I switch
> from "Color" to "Grayscale" as intended scan. This would make sense,
> because I don't have a grayscale ICC profile. Switching back from
> "Grayscale" to "Color" doesn't give me this error.
>
> It appears that when it starts, xsane tries to do something with all the
> input profiles. I think this is a bug in xsane and I'll also let the
> developper know.

The code tries to create all of the tranforms at startup so that it performs 
better.  So if a profile is missing it will issue this error message.  I 
reported this to the author perhaps 6 months ago.

>
> But in the meantime, I would like to get rid of the startup error message,
> as I am not the only one working with this scanner.
>
> So basically my question would be: where do I find a grayscale ICC profile
> ? As I have understood, Argyll doesn't support it.
> Is there a way to convert a color ICC profile (RGB or CMYK) into grayscale
> ? Or can somebody maybe send me one (possibly off-list) ?
>
> Note that for me, this profile doesn't have to be accurate at all as I
> don't scan in grayscale for now.
>
> In the long run, I may be interested in grayscale scanning as well, so
> hints on how to create a more accurate grayscale profile are welcome as
> well.
>
> Thank you,
>
> Geert

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