Export specified pages as jpg at defined resolution

Question

Hello inDesign Community -
I have a script that allows me to export pages specified from a dialog prompt as jpgs at a specific resolution (500px wide).
This is great for making thumbnails, however It uses the dimensions of the active document page to set the resolution formula.
This works unless there are different sized pages, at which point you get different sized jpg.
How can use the page dimensions of each page that is being exported individually.
I assume there is a way to get an array from jpegExportPreferences.pageString that can then be looped through.
Thanks in advance
// which pages to export
var pagesToExport
// final jpg demensions
var myLargeWidth = 500;
var myLargeHeight = 500;
// create a variable for current active document
var docRef = app.activeDocument;
// remove ententions from end of file path
myFilename = docRef.name.replace(/\.[^\.]+$/, '');
// set variable to save file in same directory as active document
myFolder = docRef.filePath;
// set document measurments to points and reset ruler orgin
docRef.viewPreferences.horizontalMeasurementUnits = MeasurementUnits.points;
docRef.viewPreferences.verticalMeasurementUnits = MeasurementUnits.points;
docRef.viewPreferences.rulerOrigin = RulerOrigin.PAGE_ORIGIN;
docRef.zeroPoint = [0,0];
//bounds    Array of Measurement Unit (Number or String)    readonly    The bounds of the Page, in the format [y1, x1, y2, x2].
// find width of page
var myCurrentWidth = app.activeWindow.activePage.bounds[3]-app.activeWindow.activePage.bounds[1];
// find height of page
var myCurrentHeight = app.activeWindow.activePage.bounds[2]-app.activeWindow.activePage.bounds[0];
function exportJPG() {
  // export large jpg
            if (myLargeWidth > 0) {
                // Calculate the scale percentage
                var myResizePercentage = myLargeWidth/myCurrentWidth;
                var myExportRes = myResizePercentage * 72;
                // exportResolution is only accurate to 1 decimal place, so round
            else {
                // Calculate the scale percentage
                var myResizePercentage = myLargeHeight/myCurrentHeight;
                var myExportRes = myResizePercentage * 72;
            // use caluclated percentage as resolution
            app.jpegExportPreferences.exportResolution = myExportRes;
            // export jpg in myfolder add .jpg to end.
            docRef.exportFile(ExportFormat.JPG, File(myFolder+"/"+myFilename+"-500px.jpg"));
            // reset back to inches
            docRef.viewPreferences.horizontalMeasurementUnits = MeasurementUnits.inches;
            docRef.viewPreferences.verticalMeasurementUnits = MeasurementUnits.inches;
var myName = myInput ();
// rest of the script
function myInput ()
  var myWindow = new Window ("dialog", "Pages to export as JPG");
  var myCommentGroup = myWindow.add ("group");
  myCommentGroup.add ("statictext", undefined, "export some jpgs", {multiline:true});
  //myCommentGroup.maximumSize.width = 200;
  var myInputGroup = myWindow.add ("group");
  myInputGroup.add ("statictext", undefined, "Pages: (1-3,8,10)");
  var myText = myInputGroup.add ("edittext", undefined, "1");
  myText.characters = 20;
  myText.active = true;
  var myButtonGroup = myWindow.add ("group");
  myButtonGroup.alignment = "right";
  myButtonGroup.add ("button", undefined, "OK");
  myButtonGroup.add ("button", undefined, "Cancel");
  if (myWindow.show () == 1)
  return myText.text, pagesToExport = myText.text;
  else
  exit ();
// jpg export preferences
app.jpegExportPreferences.exportingSpread= false;
app.jpegExportPreferences.jpegQuality = JPEGOptionsQuality.HIGH;
app.jpegExportPreferences.jpegExportRange = ExportRangeOrAllPages.EXPORT_RANGE;
app.jpegExportPreferences.pageString = pagesToExport;
app.jpegExportPreferences.embedColorProfile = false;
app.jpegExportPreferences.jpegColorSpace= JpegColorSpaceEnum.RGB;
app.jpegExportPreferences.antiAlias = true;
exportJPG();
// run function

Answer 1

Hi,
1. You need to insert myCurrentWidth & Height calculation into function exportJPG() and execute it for each page;
2. This function supposes to be run with each chosen page and different exportPreferences;
3. So  you need split a string variable pageToExport into array collecting separate pages.
Like this:
// which pages to export
var pagesToExport;
// final jpg demensions
var myLargeWidth = 500;
var myLargeHeight = 500;
// create a variable for current active document
var docRef = app.activeDocument;
// remove ententions from end of file path
myFilename = docRef.name.replace(/\.[^\.]+$/, '');
// set variable to save file in same directory as active document
myFolder = docRef.filePath;
// set document measurments to points and reset ruler orgin
docRef.viewPreferences.horizontalMeasurementUnits = MeasurementUnits.points;
docRef.viewPreferences.verticalMeasurementUnits = MeasurementUnits.points;
docRef.viewPreferences.rulerOrigin = RulerOrigin.PAGE_ORIGIN;
docRef.zeroPoint = [0,0];
function exportJPG(cPage) {
// export large jpg
//bounds    Array of Measurement Unit (Number or String)    readonly    The bounds of the Page, in the format [y1, x1, y2, x2].
// find width of page
var myCurrentWidth = cPage.bounds[3]-cPage.bounds[1];
// find height of page
var myCurrentHeight = cPage.bounds[2]-cPage.bounds[0];
if (myLargeWidth > 0) {
// Calculate the scale percentage
var myResizePercentage = myLargeWidth/myCurrentWidth;
var myExportRes = myResizePercentage * 72;
// exportResolution is only accurate to 1 decimal place, so round
else {
// Calculate the scale percentage
var myResizePercentage = myLargeHeight/myCurrentHeight;
var myExportRes = myResizePercentage * 72;
// use caluclated percentage as resolution
app.jpegExportPreferences.exportResolution = myExportRes;
app.jpegExportPreferences.pageString = cPage.name;
// export jpg in myfolder add .jpg to end.
docRef.exportFile(ExportFormat.JPG, File(myFolder+"/"+myFilename + "_" + cPage.name + "-500px.jpg"));
// SUI Dialog      
myInput ();
// jpg export preferences
app.jpegExportPreferences.exportingSpread= false;
app.jpegExportPreferences.jpegQuality = JPEGOptionsQuality.HIGH;
app.jpegExportPreferences.jpegExportRange = ExportRangeOrAllPages.EXPORT_RANGE;
app.jpegExportPreferences.embedColorProfile = false;
app.jpegExportPreferences.jpegColorSpace= JpegColorSpaceEnum.RGB;
app.jpegExportPreferences.antiAlias = true;
// run function (loop through chosen pages)
var b, c, d, stop;
b = pagesToExport.split(",");
while (c = b.shift() ) {
  d = c.split("-");
  stop = parseInt(d[0]);
  while (stop <= parseInt(d[d.length-1]) ) {
       exportJPG(docRef.pages.item(stop-1));
       stop++;
// reset back to inches
docRef.viewPreferences.horizontalMeasurementUnits = MeasurementUnits.inches;
docRef.viewPreferences.verticalMeasurementUnits = MeasurementUnits.inches;
// rest of the script
function myInput ()
  var myWindow = new Window ("dialog", "Pages to export as JPG");
  var myCommentGroup = myWindow.add ("group");
  myCommentGroup.add ("statictext", undefined, "export some jpgs", {multiline:true});
  //myCommentGroup.maximumSize.width = 200;
  var myInputGroup = myWindow.add ("group");
  myInputGroup.add ("statictext", undefined, "Pages: (1-3,8,10)");
  var myText = myInputGroup.add ("edittext", undefined, "1");
  myText.characters = 20;
  myText.active = true;
  var myButtonGroup = myWindow.add ("group");
  myButtonGroup.alignment = "right";
  myButtonGroup.add ("button", undefined, "OK");
  myButtonGroup.add ("button", undefined, "Cancel");
  if (myWindow.show () == 1)
  return pagesToExport = myText.text;
  else
  exit ();
Notice that different page sizes can lead to different width/height proportions.
In this case JPGs will still differ. (by height)
Jarek