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Roger Breton
Roger Breton
Legend
March 18, 2024
Answered

Script to convert CIE Lab to CIE Lch?

  • March 18, 2024
  • 2 replies
  • 725 views

Looking for a way to work around InDesign limited color management capability.

Suppose I have some object selected on the page, the script would have to be able to extract the CIE Lab values out of the selected object, convert to Chroma and Hue angle, and paste the values in a new text frame. Doable? Easily?

 

    This topic has been closed for replies.
    Correct answer Roger Breton

    Well, here's a simple script that displays an alert with the CIE Chroma and CIE Hue angle information.
    InDesign HSB is useless because it is based on RGB. 
    I am not by any means a JavaScript specialist.


    The code is quite simple:

    // Roger Breton / March 18 2024

    // Get the active document
    var doc = app.activeDocument;

    // Check if there's a selection
    if (doc.selection.length > 0) {
        // Get the first selected item
        var selectedItem = doc.selection[0];

        // Check if the selected item has a fill color
        if (selectedItem.fillColor !== undefined) {
            // Retrieve the fill color
            var fillColor = selectedItem.fillColor;
            var fillModel = selectedItem.fillColor.model.toString(); // SPOT
            var fillColorSpace = selectedItem.fillColor.space.toString(); // LAB
       

            var l_value = selectedItem.fillColor.colorValue[0];
            var a_value = selectedItem.fillColor.colorValue[1];
            var b_value = selectedItem.fillColor.colorValue[2];

            var l_float = parseFloat(l_value);
            var a_float = parseFloat(a_value);
            var b_float = parseFloat(b_value);

           
            // Calculate CIE Chroma (C)
            var chroma = Math.sqrt(Math.pow(a_value, 2) + Math.pow(b_value, 2));

            // Calculate Hue Angle (H) in radians
            var hue_radians = Math.atan2(b_value, a_value);

            // Convert Hue Angle to degrees
            var hue_degrees = (hue_radians * 180) / Math.PI;
            if (hue_degrees < 0) {
                hue_degrees += 360; // Make it positive
            }

            // Print the fill color details
            alert("Fill Color:\n\n" +
                  "Color Model: " + fillModel + "\n" +
                  "Color Space: " + fillColorSpace + "\n" +
                  "L : " + l_value.toFixed(2) + "\n" +
                  "A : " + a_value.toFixed(2) + "\n" +
                  "B : " + b_value.toFixed(2) + "\n" +
                  "Chroma : " + chroma.toFixed(2) + "\n" +
                  "Hue Angle : " + hue_degrees.toFixed(2) + " degrees");
        } else {
            alert("The selected item does not have a fill color.");
        }
    } else {
        alert("No item is currently selected.");
    }

    2 replies

    rob day
    Community Expert
    rob dayCommunity Expert
    Community Expert
    March 18, 2024

    Hi @Roger Breton A conversion to HSB would be the only option. InDesign’s HSB is not device independent, it’s color managed via the assigned RGB profile, so its apperance would change depending on the RGB profile assignment.

    James Gifford—NitroPress
    James Gifford—NitroPress
    Legend
    March 18, 2024

    I have no solution here but if there is one, there are a couple of color folks who will provide it.

     

    I'm just curious how extracting/calculating this fairly esoteric color value... and then just pasting in text values, is of use. For some manual entry at a later point? Seems as if any color value calculator could do that...

    Roger Breton
    Roger BretonAuthorCorrect answer
    Legend
    March 19, 2024

    Well, here's a simple script that displays an alert with the CIE Chroma and CIE Hue angle information.
    InDesign HSB is useless because it is based on RGB. 
    I am not by any means a JavaScript specialist.


    The code is quite simple:

    // Roger Breton / March 18 2024

    // Get the active document
    var doc = app.activeDocument;

    // Check if there's a selection
    if (doc.selection.length > 0) {
        // Get the first selected item
        var selectedItem = doc.selection[0];

        // Check if the selected item has a fill color
        if (selectedItem.fillColor !== undefined) {
            // Retrieve the fill color
            var fillColor = selectedItem.fillColor;
            var fillModel = selectedItem.fillColor.model.toString(); // SPOT
            var fillColorSpace = selectedItem.fillColor.space.toString(); // LAB
       

            var l_value = selectedItem.fillColor.colorValue[0];
            var a_value = selectedItem.fillColor.colorValue[1];
            var b_value = selectedItem.fillColor.colorValue[2];

            var l_float = parseFloat(l_value);
            var a_float = parseFloat(a_value);
            var b_float = parseFloat(b_value);

           
            // Calculate CIE Chroma (C)
            var chroma = Math.sqrt(Math.pow(a_value, 2) + Math.pow(b_value, 2));

            // Calculate Hue Angle (H) in radians
            var hue_radians = Math.atan2(b_value, a_value);

            // Convert Hue Angle to degrees
            var hue_degrees = (hue_radians * 180) / Math.PI;
            if (hue_degrees < 0) {
                hue_degrees += 360; // Make it positive
            }

            // Print the fill color details
            alert("Fill Color:\n\n" +
                  "Color Model: " + fillModel + "\n" +
                  "Color Space: " + fillColorSpace + "\n" +
                  "L : " + l_value.toFixed(2) + "\n" +
                  "A : " + a_value.toFixed(2) + "\n" +
                  "B : " + b_value.toFixed(2) + "\n" +
                  "Chroma : " + chroma.toFixed(2) + "\n" +
                  "Hue Angle : " + hue_degrees.toFixed(2) + " degrees");
        } else {
            alert("The selected item does not have a fill color.");
        }
    } else {
        alert("No item is currently selected.");
    }
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