[Lcms-user] Questions generating postscript files (CSA/CRD)

[Oliver R. <Oli...@ra...>]

Hello.

At frist I want to say thanks for lcms. I planned to add color correction to 
xsane since a long time but never started it until some weeks ago I took a 
look at lcms again and thought that now is the right time to try it.

Adding preview and viewer support for RGB images to xsane was much more easy 
than I expected. The most work was to think about the changes in the user 
interface of xsane.

Doing the color correction while saving the image (instead of embedding a 
profile) also does work for RGB images. (I still have problems with grayscale 
images but this has to wait in the moment).

Now I am trying to find out how to create color corrected RGB postscript 
files. I looked through the lcms mailing list and found some information in 
the message
http://sourceforge.net/mailarchive/message.php?msg_id=5763412

In the moment I try to create color corrected postscript files by hand at 
first:

1)  I create a CSA with
icc2ps -i scanner.ICM > scanner.CSA

2) I create the CRD with
icc2ps -o printer.ICM > printer.CRD

3) I have a scanned image that is saved as (non color corrected) RGB 
postscript: image.ps

now I try to create a color corrected postscript by concatening:

file "printer.CRD"
line "<< /UseCIEColor true >> setpagedevice"
file "scanner.CSA"
file "image.ps"
line "/DefaultRGB exch /ColorSpace defineresource setcolorspace"
(this is IMAGE A)

but the message above explains it a bit different (but may be there has
changed something in lcms since then):

file "printer.CRD"
remove "/Current exch /ColorRendering defineresource pop" 
(or create CRD with icc2ps -u)
add "setcolorrendering"
line "<< /UseCIEColor true >> setpagedevice"
file "scanner.CSA"
file "image.ps"
line "/DefaultRGB exch /ColorSpace defineresource setcolorspace"
(this is IMAGE B)

I do not have a color printer to test the result, so I tried to display the 
results on my screen:

- display (imagemagick) does not show any color corrections at all

- kghostview shows the original (untouched) image but does not produce any   
output for the files with CSA+CRD included

- gimp and "gs -sDEVICE=x11" show changes in the colors with CSA+CRD included,
but the images A and B look different and I can not decide on the screen which 
one is the correct one.

Question 1: What is the correct way to create a postscript file with CSA+CRD?


Question 2: How Do I produce a device independent postscipt file with an 
included CSA but without a CRD? Is it done this way:?

line "<< /UseCIEColor true >> setpagedevice"
file "scanner.CSA"
file "image.ps"
line "/DefaultRGB exch /ColorSpace defineresource setcolorspace"

The postscript headers have to be moved to the top of the file I think.


Question 3: (a bit OT, but may be you know): When I want xsane to transfer the 
postscript directly to the printer should I always prepend the CRD to the 
postscript file or does a real postscript printer know his CRD and the CRD 
should only be prepended for ghostscript? (or should the  ghostscript/printer 
deamon prepend the CRD?)


Question 4: Is it good to store the image in RGB or should I convert it to
CMYK before saving it as postscript?


Question 5: When I want to put images that are scanned with different scanners 
into one postscript file how do I apply different CSA to the different 
images? 
This way?:

"<< /UseCIEColor true >> setpagedevice"
CSA1
line "/DefaultRGB exch /ColorSpace defineresource setcolorspace"
image1
CSA2
line "/DefaultRGB exch /ColorSpace defineresource setcolorspace"
image2

Thanks for your help.

Best regards
Oliver