Auto Populate Curve Adjustment

Try this script. The active layer must be a normal layer.

app.preferences.rulerUnits = Units.PIXELS;
var len = activeDocument.width.value;
activeDocument.colorSamplers.removeAll();
activeDocument.colorSamplers.add([1,1]);
var lum = 0;
var p = new Array();
p.push([0,0]);
var n = 0;
for (var i = 0; i < len; i+=10)
    {
    activeDocument.colorSamplers[0].move([i,0]);
    var color = activeDocument.colorSamplers[0].color;
    var lm = Math.round(0.299*color.rgb.red + 0.587*color.rgb.green + 0.114*color.rgb.blue);
    if (lm != lum)
        {
        lum = lm;
        if (lum >= 255) break;
        p.push([lum,lum]);
        ++n;
        if (n >= 14) break;
        }                        
    }
p.push([255,255]);
activeDocument.colorSamplers.removeAll();
add_curves(p);
function add_curves(c)
    {
    try {
        var d = new ActionDescriptor();
        var list = new ActionList();
        function set_chnl(name, m)
            {
            if (m == undefined || m == null) return;
            var d = new ActionDescriptor();
            var r = new ActionReference();
            r.putEnumerated(stringIDToTypeID("channel"), stringIDToTypeID("channel"), stringIDToTypeID(name));
            d.putReference(stringIDToTypeID("channel"), r);
            var lst = new ActionList();
            for (var i = 0; i < m.length; i++)
                {
                if (m == undefined) continue;    
                var d1 = new ActionDescriptor();
                d1.putDouble(stringIDToTypeID("horizontal"), m[0]);
                d1.putDouble(stringIDToTypeID("vertical"),   m[1]);
                lst.putObject(stringIDToTypeID("point"), d1);
                }
            d.putList(stringIDToTypeID("curve"), lst);
            list.putObject(stringIDToTypeID("curvesAdjustment"), d);
            }
        set_chnl("composite", c);
        d.putList(stringIDToTypeID("adjustment"), list);
         
        add_adjustmen_layer("curves", d);
        } 
    catch (e) { throw(e); }
    }
function add_adjustmen_layer(type, data)
    {
    try { 
        var d = new ActionDescriptor();
        var r = new ActionReference();
        r.putClass(stringIDToTypeID("adjustmentLayer"));
        d.putReference(stringIDToTypeID("null"), r);
        var d1 = new ActionDescriptor();
        d1.putObject(stringIDToTypeID("type"), stringIDToTypeID(type), data);
        d.putObject(stringIDToTypeID("using"), stringIDToTypeID("adjustmentLayer"), d1);
        executeAction(stringIDToTypeID("make"), d, DialogModes.NO);
        } 
    catch (e) { throw(e); }
    }