Color samplers - dark, light & grey point - how to adjust curves

Question

Hi all
I've set dark, light & grey point in an image. Wondering how to adjust the curves based on the color samplers. Manually i invoke the curve dialog box and select the dark pen and choose sampler no1, select light pen and choose sampler no2, select grey pen and choose sampler no3. Any idea how this can be done in script?

Answer 1

I’m stymied by the gray point at current, it does not seem to use the measured values directly.
The white and black points seem to be straightforward and can be set easily with a Script when one knows the values.
#target photoshop
var theArray = [[17, 224], [0, 255], [27, 215], [0, 255], [28, 206], [0, 255]];
rgbCurvesLayer (theArray);
////// make rgb curves layer //////
function rgbCurvesLayer (theArray) {
// =======================================================
var idMk = charIDToTypeID( "Mk  " );
    var desc5 = new ActionDescriptor();
    var idnull = charIDToTypeID( "null" );
        var ref2 = new ActionReference();
        var idAdjL = charIDToTypeID( "AdjL" );
        ref2.putClass( idAdjL );
    desc5.putReference( idnull, ref2 );
    var idUsng = charIDToTypeID( "Usng" );
        var desc6 = new ActionDescriptor();
        var idType = charIDToTypeID( "Type" );
            var desc7 = new ActionDescriptor();
            var idpresetKind = stringIDToTypeID( "presetKind" );
            var idpresetKindType = stringIDToTypeID( "presetKindType" );
            var idpresetKindDefault = stringIDToTypeID( "presetKindDefault" );
            desc7.putEnumerated( idpresetKind, idpresetKindType, idpresetKindDefault );
        var idCrvs = charIDToTypeID( "Crvs" );
        desc6.putObject( idType, idCrvs, desc7 );
    var idAdjL = charIDToTypeID( "AdjL" );
    desc5.putObject( idUsng, idAdjL, desc6 );
executeAction( idMk, desc5, DialogModes.NO );
// =======================================================
var idsetd = charIDToTypeID( "setd" );
    var desc8 = new ActionDescriptor();
    var idnull = charIDToTypeID( "null" );
        var ref3 = new ActionReference();
        var idAdjL = charIDToTypeID( "AdjL" );
        var idOrdn = charIDToTypeID( "Ordn" );
        var idTrgt = charIDToTypeID( "Trgt" );
        ref3.putEnumerated( idAdjL, idOrdn, idTrgt );
    desc8.putReference( idnull, ref3 );
    var idT = charIDToTypeID( "T   " );
        var desc9 = new ActionDescriptor();
        var idpresetKind = stringIDToTypeID( "presetKind" );
        var idpresetKindType = stringIDToTypeID( "presetKindType" );
        var idpresetKindCustom = stringIDToTypeID( "presetKindCustom" );
        desc9.putEnumerated( idpresetKind, idpresetKindType, idpresetKindCustom );
        var idAdjs = charIDToTypeID( "Adjs" );
            var list1 = new ActionList();
                var desc10 = new ActionDescriptor();
                var idChnl = charIDToTypeID( "Chnl" );
                    var ref4 = new ActionReference();
                    var idChnl = charIDToTypeID( "Chnl" );
                    var idChnl = charIDToTypeID( "Chnl" );
                    var idRd = charIDToTypeID( "Rd  " );
                    ref4.putEnumerated( idChnl, idChnl, idRd );
                desc10.putReference( idChnl, ref4 );
                var idCrv = charIDToTypeID( "Crv " );
                    var list2 = new ActionList();
// add r points;
for (var m = 0; m < theArray[0].length; m++) {
          addCurvePoint (list2, theArray[0][m], theArray[1][m])
                desc10.putList( idCrv, list2 );
            var idCrvA = charIDToTypeID( "CrvA" );
            list1.putObject( idCrvA, desc10 );
                var desc15 = new ActionDescriptor();
                var idChnl = charIDToTypeID( "Chnl" );
                    var ref5 = new ActionReference();
                    var idChnl = charIDToTypeID( "Chnl" );
                    var idChnl = charIDToTypeID( "Chnl" );
                    var idGrn = charIDToTypeID( "Grn " );
                    ref5.putEnumerated( idChnl, idChnl, idGrn );
                desc15.putReference( idChnl, ref5 );
                var idCrv = charIDToTypeID( "Crv " );
                    var list3 = new ActionList();
// add g points;
for (var m = 0; m < theArray[2].length; m++) {
          addCurvePoint (list3, theArray[2][m], theArray[3][m])
                desc15.putList( idCrv, list3 );
            var idCrvA = charIDToTypeID( "CrvA" );
            list1.putObject( idCrvA, desc15 );
                var desc20 = new ActionDescriptor();
                var idChnl = charIDToTypeID( "Chnl" );
                    var ref6 = new ActionReference();
                    var idChnl = charIDToTypeID( "Chnl" );
                    var idChnl = charIDToTypeID( "Chnl" );
                    var idBl = charIDToTypeID( "Bl  " );
                    ref6.putEnumerated( idChnl, idChnl, idBl );
                desc20.putReference( idChnl, ref6 );
                var idCrv = charIDToTypeID( "Crv " );
                    var list4 = new ActionList();
// add b points;
for (var m = 0; m < theArray[4].length; m++) {
          addCurvePoint (list4, theArray[4][m], theArray[5][m])
                desc20.putList( idCrv, list4 );
            var idCrvA = charIDToTypeID( "CrvA" );
            list1.putObject( idCrvA, desc20 );
        desc9.putList( idAdjs, list1 );
    var idCrvs = charIDToTypeID( "Crvs" );
    desc8.putObject( idT, idCrvs, desc9 );
executeAction( idsetd, desc8, DialogModes.NO );
return app.activeDocument.activeLayer;
////// add curve point //////
function addCurvePoint (theList, valueHor, valueVer) {
var desc11 = new ActionDescriptor();
var idHrzn = charIDToTypeID( "Hrzn" );
desc11.putDouble( idHrzn, valueHor );
var idVrtc = charIDToTypeID( "Vrtc" );
desc11.putDouble( idVrtc, valueVer );
var idPnt = charIDToTypeID( "Pnt " );
theList.putObject( idPnt, desc11 );
Edit: I had assumed the gray point picker would set the input values of the point picked to output 127/127/127, but he operation seems to be quite different.