#target photoshop

function applyImageFromComponent(channelCharID, blendCharID) {
    // Apply Image: active_channel blend= source_channel (из merged visible)
    var d = new ActionDescriptor();
    var src = new ActionDescriptor();
    var srcRef = new ActionReference();
    srcRef.putEnumerated(charIDToTypeID('Chnl'), charIDToTypeID('Chnl'), charIDToTypeID(channelCharID));
    srcRef.putEnumerated(charIDToTypeID('Lyr '), charIDToTypeID('Ordn'), charIDToTypeID('Mrgd'));
    srcRef.putIdentifier(charIDToTypeID('Dcmn'), app.activeDocument.id);
    src.putReference(charIDToTypeID('T   '), srcRef);
    src.putEnumerated(charIDToTypeID('Clcl'), charIDToTypeID('Clcn'), charIDToTypeID(blendCharID));
    src.putDouble(charIDToTypeID('Scl '), 1);
    src.putInteger(charIDToTypeID('Ofst'), 0);
    d.putObject(charIDToTypeID('With'), charIDToTypeID('Clcl'), src);
    executeAction(charIDToTypeID('AppI'), d, DialogModes.NO);
}

function applyImageFromAlpha(alphaName, blendCharID) {
    var d = new ActionDescriptor();
    var src = new ActionDescriptor();
    var srcRef = new ActionReference();
    srcRef.putName(charIDToTypeID('Chnl'), alphaName);
    srcRef.putIdentifier(charIDToTypeID('Dcmn'), app.activeDocument.id);
    src.putReference(charIDToTypeID('T   '), srcRef);
    src.putEnumerated(charIDToTypeID('Clcl'), charIDToTypeID('Clcn'), charIDToTypeID(blendCharID));
    src.putDouble(charIDToTypeID('Scl '), 1);
    src.putInteger(charIDToTypeID('Ofst'), 0);
    d.putObject(charIDToTypeID('With'), charIDToTypeID('Clcl'), src);
    executeAction(charIDToTypeID('AppI'), d, DialogModes.NO);
}

function threshold(level) {
    var d = new ActionDescriptor();
    d.putInteger(charIDToTypeID('Lvl '), level);
    executeAction(charIDToTypeID('Thrs'), d, DialogModes.NO);
}

function selectCompositeRGB() {
    var d = new ActionDescriptor();
    var r = new ActionReference();
    r.putEnumerated(charIDToTypeID('Chnl'), charIDToTypeID('Chnl'), charIDToTypeID('RGB '));
    d.putReference(charIDToTypeID('null'), r);
    executeAction(charIDToTypeID('slct'), d, DialogModes.NO);
}

(function () {
    var doc = app.activeDocument;
    if (doc.mode !== DocumentMode.RGB) { alert("Нужен RGB"); return; }
    if (doc.bitsPerChannel !== BitsPerChannelType.EIGHT) { alert("Нужен 8 бит на канал"); return; }

    // === НАСТРОЙКА ===
    var DOM_INDEX  = 2;       // 0=R, 1=G, 2=B
    var DOM_CHAR   = 'Bl  ';  // charID доминирующего
    var OTHER1_CHAR = 'Rd  '; // charID первого подчинённого
    var OTHER2_CHAR = 'Grn '; // charID второго подчинённого

    // 1. alpha1 = clamp(B − R)
    var alpha1 = doc.channels[DOM_INDEX].duplicate();
    alpha1.name = "_DOM_minus_A";
    doc.activeChannels = [alpha1];
    applyImageFromComponent(OTHER1_CHAR, 'Sbtr');

    // 2. alpha2 = clamp(B − G)
    var alpha2 = doc.channels[DOM_INDEX].duplicate();
    alpha2.name = "_DOM_minus_B";
    doc.activeChannels = [alpha2];
    applyImageFromComponent(OTHER2_CHAR, 'Sbtr');

    // 3. alpha1 = min(alpha1, alpha2) через Darken
    doc.activeChannels = [alpha1];
    applyImageFromAlpha(alpha2.name, 'Drkn');

    // 4. Threshold 1: любой ненулевой → белый (строгая булевая маска)
    threshold(1);

    // 5. Загружаем как выделение
    doc.selection.load(alpha1, SelectionType.REPLACE);

    // 6. Cleanup
    alpha2.remove();
    alpha1.remove();
    selectCompositeRGB();
})();