conversion to CMYK background problem

[evgeni]

Hi,
I am trying to do a simple conversion from RGB TIFF (or png) image to CMYK JPEG, for example:

>convert sample-rgb.tiff -profile sRGB.icm -profile USWebCoatedSWOP.icc sample-cmyk.jpg

The resulting image looks correct to me, "identify" command shows that image is in cmyk indeed, and I can open this image with Photoshop without problem.
But a publishing company tells, that they cannot accept this CMYK image due to "reverse background colors". Not sure what it means, since I do not see any problem on my machine (Windows). If I convert the same tiff image with Photoshop (rgb tiff ==> cmyk jpeg), the publisher sees the right colors.

Running "identify" command on both images converted with Photoshop and ImageMagick show almost identical data. The only visible difference is, that Photoshop image contains some EXIF properties, and it is ~20% smaller than IM image (same jpeg quality).

Does this sound like a familiar problem? I also used different cmyk profiles and parameters like -background white -flatten, but with the same results.
Appreciate any help.
Thanks, Evgeni.

[fmw42]

Post links to your input and output images.

Tiff files can have different polarity: see http://www.imagemagick.org/Usage/formats/#tiff

-define quantum:polarity=min-is-black
-define quantum:polarity=min-is-white


But I don't know if these carry over to the jpg? or if this is the issue?

[evgeni]

No, polarity does not help.
Moreover, I can convert from any RGB image type (tiff, png, or jpeg) into CMYK JPEG, the resulting image still has "reverse" or "negative" colors.
I think, Mac Preview opens it with negative colors (and so does the publisher's printing software).

Photoshop opens image correctly, and also, after saving this image in Photoshop it becomes suitable for Mac Preview (and publisher) as well.

The source image: http://dev.dailyvest.com/dvpademodv/ima ... p-rgb.tiff
The result image: http://dev.dailyvest.com/dvpademodv/ima ... 2-prop.jpg


Apparently, there are some properties in the CMYK image produced by IM, that force certain software to "reverse" colors.

Thanks,
Evgeni.

[evgeni]

Hi,
Looks like there is no solution to this problem.
I've tried several other tools to create CMYK JPEG, but the image still has wrong "negative" colors on Mac.
Then, I found several articles describing similar problem, for example, http://www.zdnet.com/blog/apple/preview ... n-bug/1567

It seems like incompatibily in Mac software, which can recognize CMYK JPEG produced only by Photoshop, but not from any other tools.

I appreciate, if somebody knows a workaround such problem.

Thanks, Evgeni.

[fmw42]

The source image: http://dev.dailyvest.com/dvpademodv/ima ... p-rgb.tiff
The result image: http://dev.dailyvest.com/dvpademodv/ima ... 2-prop.jpg

I tried to convert your first image to JPG using USWebSwop.icc and sRGB profiles, but got the same results as you.

You need advice from someone smarter than I about profiles and tiff vs jpg.

[fmw42]

Turns out that Mac Preview and IM display (unix X11) don't handle this well according to my testing. But if I open it in Mac GraphicConverter it opens fine with a white background. So I think some Mac image viewers do not understand profiles or ignore them.

I tried both

convert samp-rgb.tiff -profile Profiles/sRGB.icc -profile Profiles/USWebCoatedSWOP.icc samp_rgb_sRGB2USWebCoatedSWOP.jpg

convert samp-rgb.tiff -strip -profile Profiles/sRGB.icc -profile Profiles/USWebCoatedSWOP.icc samp_rgb_strip_sRGB2USWebCoatedSWOP.jpg

and still get dark background on Mac Preview and IM display, but correct looking on PS and Mac GraphicConverter.

So I think the files are fine -- it is the viewer that is messing up.

[fmw42]

I found this text about Mac Preview.

Code: Select all

Apple Support Homeapple.com/support
Mac OS X 10.4, 10.5: Preview - TIFF images exported to JPEG may appear inverted

Symptoms

If you export CMYK images as JPEG from the Mac OS X Preview application, colors in the JPEG image may appear inverted when displayed in third-party applications.

Resolution

The color rendering of CMYK JPEGS can vary depending on the application displaying the file. If you are experiencing color inversions with your CMYK JPEG files, then it is suggested you use CMYK TIFF files instead. If you must use the JPEG format, then use Preview to convert your CMYK colors into RGB colors using the following steps: 

Open the image in Preview
Choose Tools > Match to profile...
From the Color Model pop-up menu, choose RGB
From the ColorSync Profile menu, choose Generic RGB Profile
Click OK
Save the file as a JPEG.
Note: Converting files from CMYK to JPEG may lead to changes in color appearance.

Article ID: TS1252  	Date Modified: 2009-09-25

But I tried it in my OSX Tiger 10.4 Preview but it still did not allow the image to viewed correctly.

[Drarakel]

Yeah, that's in the linked article from evgeni.

It's a problem that is probably related to the CMYK JPG displaying problem in Mac Preview. But it's not the exact same problem.
The steps in the article are not meant as solution to display correctly the CMYK JPGs that were created with e.g. ImageMagick. It's meant as workaround so that the JPGs that are created with Mac Preview (from e.g. CMYK TIFFs) don't show up as inverted in OTHER apps (not Mac Preview). If a CMYK JPG gets created by Mac Preview (so, without the workaround), this JPG shows up correctly in Mac Preview, but probably only in Mac Preview - according to the article.