Legacy ImageMagick Discussions Archive

Fred, Did you try a Google search? you may not believe it, but yes, I spent days googling on this issue. And yes, I found tons of sites presenting the equations for converting coordinates between various color spaces, but I found very little (and nothing explicit) about the topic I described in my o...

Hi there,

it might be a bit off-topic, but I'm not sure where else to ask... I wonder if anyone knows how obtain (calculate? look up?) the (L*a*b* or XYZ) coordinates of the surface of the solid representing the whole range of colors visible to the human eye.

Thanx for any advice --

-- Torsten

Hey,

snibgo wrote:I note that GenericLabProfile has DeviceClass="Color Space" where lab2lab has "Input". Maybe that is significant.

missed that one! Sounds like a reasonable explanation, thanks!

Best regards --

Torsten

Snibgo, What's the connection space? From your description, it seems that icm can only convert from lab to lab, and there's no connection space, so it couldn't be used for anything at all. in both cases the PCS is set to Lab -- at least that's how I interpret the header output by iccdump. Here's you...

Hi there, just found a file called "lab2lab.icm" on my hard disk (somewhere in argyll's folder structure). At a first glance (using iccdump) it seems to be similar to the GenericLabProfile.icc file courtesy by snibgo. One major difference is that it only contains an A2B0 tag, no B2A0 for t...

Hi there, I happen to have v6.8.8-9 installed, and confirm that it drops profiles, as you say. Most versions don't have that bug. For example, v6.8.8-7 worked fine. just compiled 6.8.9 from source, and it seems to work fine w.r.t profiles in TIFF files. Seems the 6.8.8 bug might have contributed qui...

Hi, Instead of reading both images and deleting one, it is more efficient to just read one. cool, thanks for the hint! (I really don't understand why there are so many people out there who just don't appreciate the power of the command line...) Both these commands create a tiff with embedded profile...

Hi there, back to color space -- the final frontier... ;) I would need to see your input.tiff to comment. I don't know what happens if you try to store Lab pixels in jpeg. As mentioned before, the input.tiff is available at http://www.tcrass.de/files/input.tiff . I tried to create a down-scaled vers...

Hi there, many thanks for this plethora of replies! Currently I'm on a short Easter holiday trip, and I'm not sure when I'll find the time to do some experiments based on your replies. But be assured (to say it in Arnold Schwarzenegger's words): I'll be back! ;) Hoping you'll find plenty of colorful...

Snibgo, thanks a lot for your exhaustive reply. I see somewhat clearer now, in particular with regard to the interrelationship between -profile and -colorspace. When identify shows "sRGB", it means the image will be treated as sRGB unless you do any "-profile" processing. An embe...

Hi, and thanks for all your comments. convert input.tiff -colorspace LAB <do something> -colorspace sRGB output.jpg convert input.tiff -colorspace sRGB output.jpg The former should work fine. Unfortunately, it doesn't -- when calling something like convert input.tiff -colorspace LAB -level 1%,99% -c...

D'oh! Yersterday I posted a long replay -- or, as I should rather say: I *thought* I posted a reply... However, it seems to have gone lost -- maybe I finally by accident hit "Preview" again instead of "Send". Anyway, since my brother-in-law and his family are currently visiting u...

Fred, LAB colorspace was not properly fixed until 6.7.8-2 according to the changelog at http://www.imagemagick.org/script/changelog.php. Perhaps you should upgrade as that version is over 100 versions old did the upgrade, now I'm on 6.8.8, and can do stuff like convert input.tiff -colorspace LAB <do...

Hi everyone, for about two years I've tried to understand color management in general and ImageMagick's way of handling color systems, color spaces and icc profiles in particular. It's a bit like fighting the Lernaean Hydra monster of ancient Greek mythology -- once you've successfuly solved one pro...

I never liked the way grey images were treated radically diffferent to nearly-gray images. The problem seems to be resolved in v6.8.5. I sure hope it is! (Or, at least, the treat-grayscale-as-linear smartness should be only optional.) For v6.7.9 onwards, but before 6.8.5, the general technique was:...