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Convert RBG to CMYK with use of ICC profile in PHP – Photoshop

I am currently building an online APP which allows users to pick a color for text from a usual javascript color picker. I want to convert the returned value to CMYK and I know there is not one simple run-of-the-mill method to achieve this, given there are ICC profiles and all that.

I still want to achieve a relatively useful conversion the way “most” users know from Photoshop. The profiles I want to use are “AdobeRGB” for the RGB colorspace, and “Coated Fogra39” for the CMYK colorspace.

What I want to know is, if there is any method to convert single color values from one colorspace to the other, by utilizing these two ICC profiles (which I have downloaded). There are methods to convert entire images with ImageMagick, but I am dying trying to find a way to just calculate from one color value to the other.
I am also inclined to use other means of achieving this goal if there are any ideas out there.

Thanks.

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3

Answers


  1. 0

    You could use Imagick::setImageColorSpace

    Here’s a tutorial

    Also i must warn you cmyk profile is for printing not for screening they will be differences and you can’t calculate the same as rgb ( rgb misses the black thing ) an example for black ( everyone know’s this color )
    RGB Black : 0, 0, 0,
    CMYK Black: 100%;
    But they 100% key doesn’t work the same on some printers you only need 100% on others like the one that i use a roland sp 540i i make a combination of colors to produce different types of black based on what i need because 100%key will not produce the black that everyone knows and you can test it even in photoshop / corel draw to see a difference if your screen helps u.

    Other examples:

    • Registration Black | C100 M100 Y100 K100
    • Neutral Rich Black (also known as Rich Black) | C40 M30 Y30 K100
    • Flat Black | C0 M0 Y0 K100 – This black is just made up of 100% of the black channel, with no other ink in the mix. Also known as Standard black.
    • Designer Black | C70 M50 Y30 K100 Pantone® Process Black | Spot-Color/’K100′ : This
      black is available as Pantone® Process Black C (coated), U,
      (Uncoated) and M (Matt).
    • Cool Black (also known as Black Bump) | C50 M0 Y0 K100 : This is the general-mix, but this black can also be comprised [typically] of between 20%-80% cyan.
    • Golden Black | C0 M0 Y60 K100 : This is the general-mix, but this black can also be
      comprised [typically] of between 20%-80% yellow.
    • Warm Black | C0 M60 Y0 K100 : This is the general-mix, but this black can also be
      comprised [typically] of between 20%-80% magenta.

    So you see CMYK is very different from rgb space because is used for printing and that means you will have trouble if you don’t know how it works.

    Update: ICC Profiles are for monitors not for printing ..

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  2. 0

    You can try to create a Photoshop image that consists of a series of gradients that emulate a subset of all RGB colors and then save this as a CMYK (say uncompressed TIFF so you can use the image like a lookup table). Read the color values and based on those create a set of equations that can extrapolate the destination CMYK from a lookup in this image, although that is a lot of effort, tried once and abandoned, somewhat complex… Or, give the user a reduced set of combinations and store those in a table, like all the #000 — #fff combinations, if that is acceptable for you.

    RGB — CMYK conversion is far from simple, that’s why Adobe progs cost money…

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  3. 0

    To just answer the question in your Title:

    Convert RBG to CMYK with use of ICC profile in PHP

    You can use the commandline via a system() call:

    <?php
system('convert inputfile.png -profile sRGB.icc -profile CoatedFOGRA39.icc -units PixelsPerInch -density 600 outputfile.pdf');

    This will work on Linux with imagemagick installed

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