Legacy ImageMagick Discussions Archive

It does not seem correct that you start with unbiased values and end up with biased ones.

What happens if you start with biased values?

Okay, here are the results. I have updated to the last beta version. Seems the white issue is solved. Even the 8bit CIELab images now have correct white values ...

see the bug report at http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=25830
This is fixed now. But it doesn't help to solve the issue. I think the explanation from GreenKoopa is right

http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=23289&start=15#p97927

The issue ...

Ah, you are right, that fixed the problem. Thanks.

I wouldn't expect such an hard fail, if I didn't have the latest libpng installed. The earlier behavior: issuing a warning but returning cli code 0 is somewhat more friendly. I didn't know enough about installing, configure and make files - Would ...

IM fails sometimes when working with png images with wrong profiles.
This isn't a new issue. In earlier versions, identify issues a warning and send and cli return code 0. Thats okay and one can work around the warnings. In the current version (stable and beta) this isn't the case anymore. IM ...

snibgo wrote:What type of printer is it?

Its an Stork inkjet textile printer Ruby V - based on Mimaki JV5. I have contacted the support people to help me with some question regarding the RIPSoftware. Waiting for more infos.

IM uses 50% biased values. So I am not sure it txt: is fixed or not. I don't think the zero biased values are not going to work correctly when used to define colors via xc: or canvas:.

I think I didn't get the hold biased thing right :?

I tried the 50% biased values (i hope)

$ convert xc ...

I see, this is fixed now in beta from today. [edit: not fixed]

$ convert -size 1x1 xc:white -colorspace Lab txt:
# ImageMagick pixel enumeration: 1,1,65535,cielab
0,0: (99.9985%,0.0030518%,-0.00762951%) #FFFE00020000 cielab(99.9985%,0.0030518%,-0.00762951%)

$ convert -size 1x1 xc:white -colorspace ...

Okay. Thanks again - very much. That issue drives me crazy these days.

It's a storck textile printer. (I'm not sure if its based on a mimaki model) I don't know the exact Model yet. I will try to get more information. But I'm afraid that needs until tomorrow.

We stripped the data and get some ...

http://we.tl/8DbhSXIEVU

rgb.png is the white pixel

ps-lab.tif - the file generated with PS, prints fine

im-lab-16bit.tif - file generated with IM 16 Bit, prints very light shadow of something
im-lab-8bit.tif - file generated with IM 8 Bit, prints very light shadow of something

convert rgb.png ...

The rounding error from IM is 4 parts in 65536, or 1 part in 16,000. This would not be visible, and is far less than 1 part in 127.

Hmm, in every direction an dead end. :(

For testing reason we converted one file - 1px rgb white - with photoshop to lab, tif - and one file whith IM. The file ...

What gives you "100,0,-1"?

What version of IM are you running?

Whit cielab notation I mean the one that takes the central value of the a* and b* channels as 0 and the max/min values as -127,127. That what IM generates as white is 100,0,-1 - a light shade of blue, when in get printed. The printer ...

The calculator at http://www.brucelindbloom.com/index.html?ColorCalculator.html takes the central value of the a* and b* channels as 0, with values being positive or negative. In current IM, the central values are 50%, not zero.

In Lab space, the triplet (x,50%,50%), using the IM convention, is a ...

Okay, thanks. I will try to get someone who knows something about the printers. I 'll come back, if I have a solution or another questions. Thanks so far.

1: (255,127,127) #FFFFFF cielab(255,127,127)
No. #FFFFFF isn't 255,127,127.

Whatever the correct numbers are. It should be pure white, but it is not.

These printers use LAB colorspace and they know exactly what white is.
So ask your printers, and use that value.

Sounds somewhat angry ...

Sorry, but I have to come back.

Background: We creates the .tif files for use in textile printers. These printers use LAB colorspace and they know exactly what white is.

Problem: all the above solutions gives us a background that is visually (on screen) white, but not for a LAB aware printer.

I ...