Convert an image to an 'informative'color gradient

You could try this:

// create rectangular shapes representing percentages of the (composite) histogram;

// 2017, use it at your own risk;

#target photoshop

if (app.documents.length > 0) {

var originalRulerUnits = app.preferences.rulerUnits;

app.preferences.rulerUnits = Units.PIXELS;

var myDocument = app.activeDocument;

var theName = myDocument.name;

try {var theName = theName.match(/(.*)\.[^\.]+$/)[1]} catch (e) {};

try {var thePath = myDocument.path}

catch (e) {var thePath = "~/Desktop"};

var theTotal = myDocument.width * myDocument.height;

// the values;

var theArray = new Array;

if (myDocument.mode == DocumentMode.MULTICHANNEL || myDocument.mode == DocumentMode.GRAYSCALE) {

  var theHistogram = myDocument.channels[0].histogram

  };

else {var theHistogram = myDocument.histogram};

// get total number of histogram:

var theNumber = 0;

for (var m = 0; m < theHistogram.length; m++) {

  var thisValue = theHistogram;

  theArray.push(thisValue);

  theNumber = theNumber + theHistogram

  };

if (theNumber != theTotal) {alert ("something’s wrong")}

else {};

// create shape layers;

var theX = myDocument.width;

var theWidth = myDocument.width;

var theBottom = myDocument.height;

var theTotal = theWidth * theBottom;

for (var n = 0; n < theArray.length; n++) {

// only if non-zero;

if (theArray != 0) {

var thePerc = theArray / theTotal;

rectangleShapeLayer ([0,0,theX,theBottom], n, n, n);

theX = theX - (thePerc * theWidth);

}

};

// reset;

  app.preferences.rulerUnits = originalRulerUnits;

  }

else {

  alert ("no open document")

  };

////// rectangle //////

function rectangleShapeLayer (theArray, theR, theG, theB) {

// =======================================================

var idMk = charIDToTypeID( "Mk  " );

    var desc44 = new ActionDescriptor();

    var idnull = charIDToTypeID( "null" );

        var ref9 = new ActionReference();

        var idcontentLayer = stringIDToTypeID( "contentLayer" );

        ref9.putClass( idcontentLayer );

    desc44.putReference( idnull, ref9 );

    var idUsng = charIDToTypeID( "Usng" );

        var desc45 = new ActionDescriptor();

        var idType = charIDToTypeID( "Type" );

            var desc46 = new ActionDescriptor();

            var idClr = charIDToTypeID( "Clr " );

                var desc47 = new ActionDescriptor();

                var idRd = charIDToTypeID( "Rd  " );

                desc47.putDouble( idRd, theR );

                var idGrn = charIDToTypeID( "Grn " );

                desc47.putDouble( idGrn, theG );

                var idBl = charIDToTypeID( "Bl  " );

                desc47.putDouble( idBl, theB );

            var idRGBC = charIDToTypeID( "RGBC" );

            desc46.putObject( idClr, idRGBC, desc47 );

        var idsolidColorLayer = stringIDToTypeID( "solidColorLayer" );

        desc45.putObject( idType, idsolidColorLayer, desc46 );

        var idShp = charIDToTypeID( "Shp " );

            var desc48 = new ActionDescriptor();

            var idunitValueQuadVersion = stringIDToTypeID( "unitValueQuadVersion" );

            desc48.putInteger( idunitValueQuadVersion, 1 );

            var idTop = charIDToTypeID( "Top " );

            var idPxl = charIDToTypeID( "#Pxl" );

            desc48.putUnitDouble( idTop, idPxl, theArray[1] );

            var idLeft = charIDToTypeID( "Left" );

            desc48.putUnitDouble( idLeft, idPxl, theArray[0] );

            var idBtom = charIDToTypeID( "Btom" );

            desc48.putUnitDouble( idBtom, idPxl, theArray[3] );

            var idRght = charIDToTypeID( "Rght" );

            desc48.putUnitDouble( idRght, idPxl, theArray[2] );

            var idtopRight = stringIDToTypeID( "topRight" );

            desc48.putUnitDouble( idtopRight, idPxl, 0.000000 );

            var idtopLeft = stringIDToTypeID( "topLeft" );

            desc48.putUnitDouble( idtopLeft, idPxl, 0.000000 );

            var idbottomLeft = stringIDToTypeID( "bottomLeft" );

            desc48.putUnitDouble( idbottomLeft, idPxl, 0.000000 );

            var idbottomRight = stringIDToTypeID( "bottomRight" );

            desc48.putUnitDouble( idbottomRight, idPxl, 0.000000 );

        var idRctn = charIDToTypeID( "Rctn" );

        desc45.putObject( idShp, idRctn, desc48 );

    desc44.putObject( idUsng, idcontentLayer, desc45 );

    var idLyrI = charIDToTypeID( "LyrI" );

    desc44.putInteger( idLyrI, 5 );

executeAction( idMk, desc44, DialogModes.NO );

};