Legacy ImageMagick Discussions Archive

I spoke to the printing company. It's definitely ok with an image, though in that case they'd prefer tif format, 300dpi and a CYMK profile. So in addition to the resizing, units, density and profile we need to convert the image from PNG to TIF right?

try this

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pdfimages -png poster-308.pdf poster_300
convert poster_300-000.png -resize 1984x2835 -compress lzw \
-profile /Users/fred/images/profiles/sRGB.icc \
-profile /Users/fred/images/profiles/USWebCoatedSWOP.icc \
-units pixelsperinch -density 300 new_poster_300_000.tif

DarrenPotter wrote:Fortunately the original PNGs are created on the server so we don't need to extract them from the PDF.

Good. So use that PNG. Ignore the PDF.

DarrenPotter wrote:...they'd prefer tif format, 300dpi and a CYMK profile.

Something like this:

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magick in.png -density 300 -profile sRGB.icc -profile USWebUncoated.icc out.tif

Thanks guys. We'll give this a go and let you know the outcome!

Hi guys,

I've been swamped with other projects so haven't had chance to test things out fully until now. We're now able to convert the source PNG file to TIF using CMYK colorspace and the PSOcoated_v3.icc colour profile, which is great! I've noticed, however, that the colour between source PNG and output TIF is quite different - it's much darker.

The developers are running two commands to complete the conversion:

magick ‘poster.png’ -resize ‘img_width’x’img_height’ -units “PixelsPerInch” -density 300 -colorspace CMYK ‘poster.tif’
magick ‘poster.tif’ -profile /home/visio/public_html/PSOcoated_v3.icc ‘poster.tif’

Not sure if this is necessary or if anything is missing/incorrect. Does anything stand out or do you have any suggestion how we can prevent the colour distortion?

Darren

I would avoid using -colorspace CMYK. It is not as good as using profiles only. Can you post a link to your original poster.png, so we can test with it.

Also what version of IM 7 are you using?

As Fred says. You use "-colorspace" to do an simple conversion from sRGB (I assume) to CMYK, then assign a CMYK profile. A better method is to assign an sRGB profile, then use a second "-profile" to convert from that to a CMYK profile.

I will add one more thing to what snibgo said. You should add the sRGB profile only if your PNG does not already have an icc or icm profile. Note, you should resize in RGB colorspace rather than CMYK.

So if no profile, then

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magick ‘poster.png’ -profile /home/visio/public_html/sRGB.icc -resize ‘img_width’x’img_height’ -profile /home/visio/public_html/PSOcoated_v3.icc -units “PixelsPerInch” -density 300 ‘poster.tif’

If it already has a profile, then

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magick ‘poster.png’ -resize ‘img_width’x’img_height’ -profile /home/visio/public_html/PSOcoated_v3.icc -units “PixelsPerInch” -density 300 ‘poster.tif’

You can check beforehand by using

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magick poster.png -format "%[profiles]\n" info:

Hey guys,

Fantastic feedback. Thank you!

I'll get on to checking those various points. In the meantime here's a link to the original poster: https://www.dropbox.com/s/y1t20vtag8pqh ... 4.png?dl=0.

This works fine for me on IM 7.0.7.28 Q16 HDRI with no messages

magick poster.png -alpha off -profile /Users/fred/images/profiles/sRGB.icc -resize 100% -profile /Users/fred/images/profiles/USWebCoatedSwop.icc -units PixelsPerInch -density 300 poster.tif

The result looks fine to me. I turned your alpha off, since it was fully opaque. I resized 100% since I did not know your values. I used USWebCoatedSwop.icc, since I did not have your profile.

Perhaps you need to upgrade your version of IM 7.

Hey Fred,

We are using ImageMagick 7.0.7-22 Q16. The command we're now using is:

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magick ‘poster.png’ -alpha off -profile /home/visio/public_html/sRGB.icc -resize ‘img_width’x’img_height’ -profile /home/visio/public_html/PSOcoated_v3.icc -units “PixelsPerInch” -density 300 ‘poster.tif’

I'm still getting the colour distortion though, so I wonder if it has something to do with the icc profile. You can see the image here:

https://www.dropbox.com/s/c7n9jm8ao88tf ... s.png?dl=0

The larger image in the background is the source PNG, the slightly smaller image offset to the right is the processed tif and the block of blue is to illustrate the intended result for the background colour (look along the bottom edge) and you should see the difference pretty clearly.

Here's the icc profile we're using: https://www.dropbox.com/s/4ngdmvawe3ltf ... 3.icc?dl=0

Would you mind seeing if you get the same result? If so, then I guess that means we've nailed the command, but I'll need to follow up with the printing company.

Thanks once again for your help!!

Darren

Both these commands work fine for me. I am using IM 7.0.7-28 on Mac OSX.

magick poster.png -alpha off -profile /Users/fred/images/profiles/sRGB.icc -resize 100% -profile /Users/fred/images/profiles/USWebCoatedSwop.icc -units PixelsPerInch -density 300 poster1.tif

magick poster.png -alpha off -profile /Users/fred/images/profiles/sRGB.icc -resize 100% -profile /Users/fred/desktop/PSOcoated_v3.icc -units PixelsPerInch -density 300 poster2.tif

What is your version of LCMS? I am using lcms2 @2.8_0

Try upgrading that or upgrade IM 7.

See http://www.littlecms.com

Hey Fred,

We had very recent versions of both, though have updated to be on the safe side. Which sRGB.icc file are you using? There are a few to choose from it seems (e.g. http://www.color.org/srgbprofiles.xalter). Could be we aren't using the same ones.

Darren

To be honest I am not sure. I think it is v2 from http://color.org/srgbprofiles.xalter. Here is the one I used, but since it is not labeled fully, I don't know if I had it on my system or got it elsewhere.

http://www.fmwconcepts.com/misc_tests/sRGB.icc.zip

wrote:I'll get on to checking those various points. In the meantime here's a link to the original poster: https://www.dropbox.com/s/y1t20vtag8pqh ... 4.png?dl=0

I downloaded that file, poster-424.png. It is grayscale. So where does the blue come from?

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