Legacy ImageMagick Discussions Archive

Hello,

my objective is to convert a rather large separated CMYK TIFF to a PDF/X. But I have trouble preserving the original color.
The TIFF (tiny example hosted here: http://s000.tinyupload.com/index.php?fi ... 8378913311

This image was created with LibTiff using the euqations from this adress: http://www.rapidtables.com/convert/colo ... o-cmyk.htm

When using the command however, the resulting PDF displays the image washed out: http://s000.tinyupload.com/index.php?fi ... 1380781569

It is actually supposed to look like this reference RGB PNG: http://s000.tinyupload.com/index.php?fi ... 3172762386

Is it a poorly created TIFF? Why is it displayed differently by different SW? Is the TIFF pixel data alright but missing metadata to instruct how to read the CMYK? Should I use different equations to derive values for CMYK from RGB?

Also, I intend to use the following command (ghostscript of an texlive 2014 install) to convert the PDF to PDF/X. If you can spot a mistake there too, please let me know.

Thanks in advance

Unfortunately, your Tiff file has no CMYK profile. So tryy these two commands.

and
Those seem to be the best I can suggest (converting the result to sRGB) before saving to PDF.

Alright, I believe to have fixed one mistake. But I am unfamiliar with printing processes and cannot confirm to have done it properly.

Now I start with a regular RGB TIFF picture: http://s000.tinyupload.com/index.php?fi ... 1465453427

Then I downloaded an RGB working space profile called "eciRGB_V2" and an offset profile called "PSO Coated v3" from this site: http://www.eci.org/doku.php?id=en:downloads

Both were used in this command line to create an output file File here: http://s000.tinyupload.com/index.php?fi ... 2634523756
Color now seems to be a little off, but at least black stayed black.

With the ps2pdf command from my previous post I could create following file: http://s000.tinyupload.com/index.php?fi ... 2354472944

Unfortunately, I do not know how to verify that this file is now a valid PDF/X with CMYK content.

Was my approach correct this time? How do I know which profile is correct for printing on a PVC banner? Is offset coated correct or is it uncoated or is it gravure?

Thanks in advance

fmw42 wrote:Unfortunately, your Tiff file has no CMYK profile. So tryy these two commands.

Sorry, I did not make my intentions very clear.
The source file is written via a little program I wrote via libtiff. So I am somewhat in control of the properties of this file. If RGB is better suited for this task, I could simply write an RGB file. If it's recommended to use a custom tone mapper, transfer function or gamma curve, I could easily implement one.
It's the target that has to meet certain standards. It has to be PDF/X (X-1a, X-3 or X-4) and CMYK. And I believe I need an offset printing profile because it will be printed on a PVC banner (not quite sure about the choice of profile, though).

Due to my lack of expierence, I need some pointers on how to inspect the result to verify whether or not the resulting PDF actually is what I am going for.

matthiasb wrote:And I believe I need an offset printing profile because it will be printed on a PVC banner (not quite sure about the choice of profile, though).

Can't you ask whoever will do the printing?