Interacting with overprint using scripts

Studying this script might help:

https://www.marspremedia.com/software/illustrator/change-overprint

Hi @Dylan33363180v1v2, it is a little more fiddly than you might expect, just because you have to get at the overprint setting differently for different page items. You will see in the following script that I wrote to do what you are asking. Let me know if this works for you.

- Mark

/**
 * Set overprint for page items.
 * @author m1b
 * @discussion https://community.adobe.com/t5/illustrator-discussions/interacting-with-overprint-using-scripts/m-p/14206629
 */
(function () {

    var OVERPRINT_SETTING = false;

    var doc = app.activeDocument;

    // example usage 1: selection
    var items = itemsInsideGroupItems(doc.selection);

    // example usage 2: all page items in document
    // var items = itemsInsideGroupItems(doc.pageItems);

    for (var i = 0; i < items.length; i++)
        setOverprintOfItem(items[i], OVERPRINT_SETTING);

})();


/**
 * Sets item's overprinting to `value`.
 * @author m1b
 * @version 2023-11-04
 * @param {PageItem} item - an Illustrator page item.
 * @param {Boolean} value - the value to set to.
 * @returns {Object} -  {fillColors: Array<Color>, strokeColors: Array<Color>}
 */
function setOverprintOfItem(item, value) {

    if (item == undefined)
        throw Error('getBasicColorablesFromItem: No `item` supplied.');

    // collect all the overprintables
    if (item.constructor.name == 'PathItem') {
        setOverprint(item, value);
    }

    else if (
        item.constructor.name == 'CompoundPathItem'
        && item.pathItems
    ) {
        setOverprint(item.pathItems[0], value);
    }

    else if (
        item.constructor.name == 'TextFrame'
        && item.textRanges
    ) {
        var ranges = getTextStyleRanges(item.textRange, ['overprintFill', 'overprintStroke']);
        for (var i = ranges.length - 1; i >= 0; i--)
            setOverprint(ranges[i], value);
    }

    else if (item.constructor.name == 'GroupItem') {
        for (var i = 0; i < item.pageItems.length; i++)
            setOverprint(item.pageItems[i], value);

    }

    // helper function
    function setOverprint(item, value) {

        // most basic page items
        if (item.hasOwnProperty('fillOverprint')) {
            item.fillOverprint = value;
            item.strokeOverprint = value;
        }

        // text style ranges
        else if (item.hasOwnProperty('overprintFill')) {
            item.overprintFill = value;
            item.overprintStroke = value;
        }

    };

};


/**
 * Returns an array containing items,
 * including items found inside GroupItems.
 * Optionally can supply a filter function.
 * @author m1b
 * @param {Array<PageItem>} items - the starting items, may include group items.
 * @param {Function} [filter] - whether to collect item (default: collect all).
 * @returns {Array<PageItem>}
 */
function itemsInsideGroupItems(items, filter) {

    var found = [];

    for (var i = 0; i < items.length; i++) {

        var item = items[i];

        if (item.typename == 'GroupItem')
            found = found.concat(itemsInsideGroupItems(item.pageItems, filter));

        else if (
            filter == undefined
            || filter(item)
        )
            found.push(item);

    }

    return found;

};

/**
 * Returns an array of TextRanges,
 * determined by mapping changes
 * in supplied keys. For example,
 * supplying the 'fillColor' key
 * will return ranges divided when
 * the text's fillColor changes.
 * @author m1b
 * @version 2023-04-26
 * @param {TextRange} textRange - an Illustrator TextRange.
 * @param {Array<String>} keys - an array of keys to match, eg ['fillColor'].
 */
function getTextStyleRanges(textRange, keys) {

    if (
        textRange == undefined
        || textRange.constructor.name != 'TextRange'
    )
        throw Error('getTextStyleRanges: bad `textRange` supplied.');

    if (
        keys == undefined
        || keys.constructor.name != 'Array'
    )
        throw Error('getTextStyleRanges: bad `textRange` supplied.');

    // check keys are valid
    for (var j = 0; j < keys.length; j++)
        if (!textRange.characterAttributes.hasOwnProperty(keys[j]))
            throw Error('getTextStyleRanges: bad key supplied ("' + keys[j] + '")');

    var ranges = [],
        start = 0,
        currentValues = {};

    charactersLoop:
    for (var i = 0; i < textRange.length; i++) {

        var tr = textRange.textRanges[i],
            matches = true;

        // check each key
        keysLoop:
        for (var j = 0; j < keys.length; j++) {

            if (i == 0)
                currentValues[keys[j]] = tr.characterAttributes[keys[j]];

            else if (stringify(tr.characterAttributes[keys[j]]) !== stringify(currentValues[keys[j]])) {
                matches = false;
                break keysLoop;
            }
        }

        currentValues[keys[j]] = tr.characterAttributes[keys[j]];

        if (
            i == textRange.length - 1
            || !matches
        ) {
            // start a new range
            var newTextRange = textRange.textRanges[start];
            newTextRange.end = i == textRange.length - 1 ? i + 1 : i;
            ranges.push(newTextRange);
            start = i;
        }

    }

    return ranges;

};


/**
 * Stringify tailored for the purpose of
 * identifying overprintable text ranges.
 * @author m1b
 * @version 2023-04-26
 * @param {Object} obj - the object to stringify.
 * @returns {String}
 */
function stringify(obj) {

    var str = obj.toString();

    for (var key in obj) {

        if (!obj.hasOwnProperty(key))
            continue;

        if (
            key == 'overprintFill'
            || key == 'overprintStroke'
        )
            str += stringify(obj[key]);

        else
            str += obj[key];

    }

    return str;

};