Recently I’ve been working on a client project that creates branding guides via scripting. Questions about Pantone CMYK and RGB color simulations of the solid inks come up occasionally from users wanting there to be an "official" set of conversion values. There are various conversion charts available on the web—including Pantone’s own Bridge libraries—all of which have color management problems because they usually assume the appearance of RGB and CMYK values is the same for all devices. For the Pantone + Bridge process CMYK simulation libraries Pantone doesn’t provide any information on what the expected press conditions are, and the Bridge CMYK values display inconsistently relative to the more accurate solid ink Lab color display.
For the scripted guide I have defined the expected CMYK and RGB destinations for the converted values—only Lab defined swatches are addded to the guide. Each swatch label includes two CMYK values—the default conversions are to Coated GRACol 2013 and Uncoated GRACol 2013. There is also a conversion from Lab to sRGB, the sRGB’s HEX value, and a note on whether the solid ink color is outside of the coated CMYK color space’s gamut.
The format is this:
You can download a zip archive of the InDesign Pantone swatch book (2443 colors) along with more detailed notes, the default GRACol 2013 profiles, and the JavaScript here. The guide’s fonts are the Vista Sans family available from Adobe Type—there are also a PDF/X-4 versions for different press conditions:
The script dialog
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Yes the conversions are from Pantone’s Solid Color Lab values, which would be instrument read from the printed solid inks. I used Relative Colorimetric and Black Point Compensation for the conversions—the Intent and BPC would have an affect on the final CMYK values when the color is out-of-gamut to the destination CMYK space.
How do you identify if a color is within range?
If you mean is the color in the CMYK gamut, you can use the Color panel to check gamut.
If you set the Pantone color to Lab in the Color panel out-of-gamut colors get a yellow triangle. The gamut would be defined by the document’s assigned CMYK profile—uncoated would be smaller than coated.
My AppleScript does a Lab>CMYK>Lab conversion and checks if the returned Lab values have changed significantly—changed Lab values would indicate the color is out-of-gamut and I note it in the chart.
Sorry to hear the script isn’t running for you. What OS are you using? I haven’t tested on Catalina.
Make sure you have a document open and the Swatch panel contains the Pantone swatches you want to get.
Hi @Jens Trost I’ve converted the Branding Guide script to JavaScript and it is running much faster—20 min for the 2,350 swatch Pantone library—and I’ve included charts for Fogra, GRACol, PSO V3, US Sheetfed, and US Web SWOP in the linked directory.
I’ve also added dropdowns for choosing any coated and uncoated CMYK profile combinations.
If you get a chance test it and let me know if there are any problems
You are right the rendering intent I’m setting with the document creation isn’t doing anything. But if you want to change the rendering intent and black point compensation to affect the color conversions, look at my setPrefs() function where I am setting up the Color Settings before the documents are created—the Color Settings is handling the Rendering Intent on the conversions.
So this is Relative Colorimetric with BPC on vs. Absolute Colorimetric with BPC off:
There can be a "stickiness" with InDesign color conversions—round trips are not always accurate—that’s why I created a separate document to get the uncoated values
Okay, as I discovered this a while back I also tried changing the app settings instead of the document settings, but it didn't have an affect
There is a problem/bug with making conversions via the UI, which might be related. Try making a built CMYK swatch that is black only—something like 0|0|0|40—convert it to Lab and then back to CMYK. I get the original 0|0|0|40 CMYK values on the round trip via the UI:
If I make the round trip via JS I get the correct color managed conversions:
var s = app.documents.item(0).selection[0];
s.fillColor.space = ColorSpace.LAB
s.fillColor.space = ColorSpace.CMYK
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