Query Curves Layer for current settings

Question

Hi All,
I am trying to work out how to query a curves layer for it's current settings. I have used the script listner to capture the code on how to apply settings but can't work out how to query the settings. The output from the script listner when applying new settings is as follows:
// =======================================================
var idsetd = charIDToTypeID( "setd" );
    var desc19 = new ActionDescriptor();
    var idnull = charIDToTypeID( "null" );
        var ref13 = new ActionReference();
        var idAdjL = charIDToTypeID( "AdjL" );
        var idOrdn = charIDToTypeID( "Ordn" );
        var idTrgt = charIDToTypeID( "Trgt" );
        ref13.putEnumerated( idAdjL, idOrdn, idTrgt );
    desc19.putReference( idnull, ref13 );
    var idT = charIDToTypeID( "T   " );
        var desc20 = new ActionDescriptor();
        var idAdjs = charIDToTypeID( "Adjs" );
            var list3 = new ActionList();
                var desc21 = new ActionDescriptor();
                var idChnl = charIDToTypeID( "Chnl" );
                    var ref14 = new ActionReference();
                    var idChnl = charIDToTypeID( "Chnl" );
                    var idChnl = charIDToTypeID( "Chnl" );
                    var idCmps = charIDToTypeID( "Cmps" );
                    ref14.putEnumerated( idChnl, idChnl, idCmps );
                desc21.putReference( idChnl, ref14 );
                var idCrv = charIDToTypeID( "Crv " );
                    var list4 = new ActionList();
                        var desc22 = new ActionDescriptor();
                        var idHrzn = charIDToTypeID( "Hrzn" );
                        desc22.putDouble( idHrzn, 0.000000 );
                        var idVrtc = charIDToTypeID( "Vrtc" );
                        desc22.putDouble( idVrtc, 0.000000 );
                    var idPnt = charIDToTypeID( "Pnt " );
                    list4.putObject( idPnt, desc22 );
                        var desc23 = new ActionDescriptor();
                        var idHrzn = charIDToTypeID( "Hrzn" );
                        desc23.putDouble( idHrzn, 127.000000 );
                        var idVrtc = charIDToTypeID( "Vrtc" );
                        desc23.putDouble( idVrtc, 127.000000 );
                    var idPnt = charIDToTypeID( "Pnt " );
                    list4.putObject( idPnt, desc23 );
                        var desc24 = new ActionDescriptor();
                        var idHrzn = charIDToTypeID( "Hrzn" );
                        desc24.putDouble( idHrzn, 255.000000 );
                        var idVrtc = charIDToTypeID( "Vrtc" );
                        desc24.putDouble( idVrtc, 255.000000 );
                    var idPnt = charIDToTypeID( "Pnt " );
                    list4.putObject( idPnt, desc24 );
                desc21.putList( idCrv, list4 );
            var idCrvA = charIDToTypeID( "CrvA" );
            list3.putObject( idCrvA, desc21 );
        desc20.putList( idAdjs, list3 );
    var idCrvs = charIDToTypeID( "Crvs" );
    desc19.putObject( idT, idCrvs, desc20 );
executeAction( idsetd, desc19, DialogModes.NO );
I want to query the Hrzn and Vrtc parameters for 0, 127 and 255 on an existing curves layer.
Any help in working out how to do this would be greatly appreciated.
Thx in advance.

Answer 1

This is a bit of a hack but it should give you a place to start.
// Works with RGB or CMYK images.
// Does not work at all with greyscale, or indexColor
// Does not work correctly with Lab
function convertBCD( num ){
    var res = new Array;
    if(num > 16 ){
        res.unshift(1);
        num = num - 16;
    }else{
        res.unshift(0);
    if(num > 8 ){
        res.unshift(1);
        num = num - 8;
    }else{
        res.unshift(0);
    if(num > 4 ){
        res.unshift(1);
        num = num - 4;
    }else{
        res.unshift(0);
    if(num > 2 ){
        res.unshift(1);
        num = num - 2;
    }else{
        res.unshift(0);
    if(num == 1 ){
        res.unshift(1);
    }else{
        res.unshift(0);
    return res;
function getCurve( numberOfPoints ){
    this.getPoints = function(){
        this.tempArray = new Array;
        this.tempArray.push( rawDesc.charCodeAt( pointer ) );
        pointer = pointer + 2;// set pointer to next point
        this.tempArray.push( rawDesc.charCodeAt( pointer ) );
        return this.tempArray;
    this.pointsArray = new Array;
    for( var i = 0; i < numberOfPoints; i++ ){
        pointer = pointer + 2;// next point
        this.pointsArray.push( this.getPoints() );
    pointer = pointer + 2;// next curve
    return this.pointsArray;
var ref = new ActionReference();
ref.putEnumerated( charIDToTypeID( 'Lyr ' ), charIDToTypeID( 'Ordn' ), charIDToTypeID( 'Trgt' ) );
var rawDesc = executeActionGet( ref ).getList( stringIDToTypeID( 'adjustment' ) ).getObjectValue( 0 ).getData( stringIDToTypeID( 'legacyContentData' ) );
var pointer = 2;// used to read rawData similar to reading a file
var flag = rawDesc.charCodeAt( pointer );// char at offset 2 always == 1 so use to validate data
if( flag != 1 ) forceError;// unknown problem with rawData
    pointer = 6;// update pointer to BCD byte
    var bcd = rawDesc.charCodeAt( pointer );
    if( bcd < 0 || bcd > 31 ) forceError;// check for valid value
    if( bcd == 0 ) forceError;// an empty adjustment - no curves to process
    var bcdArray = convertBCD( bcd );
    var numberOfCurves = bcdArray.toString().match(/(1)/g).length;
    var curvesArray = new Array;
    pointer = 8;// set pointer to start of curve data
    for(var i = 0; i < numberOfCurves; i++ ){
        var numberOfPoints = rawDesc.charCodeAt( pointer );
        curvesArray.push( getCurve( numberOfPoints ) );
// now need to map rawData curves in curvesArray to known channel curves
var acvArray = new Array;
if( bcdArray[0] == 1 ) {
    acvArray.push( curvesArray.shift() );
} else {
    acvArray.push( [ [0,0],[255,255] ] );
if( bcdArray[1] == 1 ) {
    acvArray.push( curvesArray.shift() );
} else {
    acvArray.push( [ [0,0],[255,255] ] );
if( bcdArray[2] == 1 ) {
    acvArray.push( curvesArray.shift() );
} else {
    acvArray.push( [ [0,0],[255,255] ] );
if( bcdArray[3] == 1 ) {
    acvArray.push( curvesArray.shift() );
} else {
    acvArray.push( [ [0,0],[255,255] ] );
if( bcdArray[4] == 1 ) {
    acvArray.push( curvesArray.shift() );
} else {
    acvArray.push( [ [0,0],[255,255] ] );
if(app.activeDocument.mode == DocumentMode.RGB){
    var cNames = ['RGB','Red','Green','Blue'];
    for(c=0;c<acvArray.length-1;c++){
        alert(cNames[c]+': '+acvArray[c]);
if(app.activeDocument.mode ==  DocumentMode.CMYK){
    var cNames = ['CMYK','Cyan','Magenta','Yellow','Black'];
    for(c=0;c<acvArray.length;c++){
        alert(cNames[c]+': '+acvArray[c]);