Remove first bounds in Script

Do all the images contain frames? 

Then it might be possible to automate the measurement via a Work Path without manual input. 

Using ExtendScript you could do the following:

Step 4:- Save the selection bounds to a variable

Step 5:- Invert the selection

Step 6:- Make an intersecting selection with a rectangular marquee using the bounds + an offset

Result: you will now have only the inside of the frame selected (the place where the painting would go)

selectInterior = function () {
    var ADselector = new ActionDescriptor();
    var ARlayerRef = new ActionReference();
    var ARchannelRef = new ActionReference();
    ARlayerRef.putProperty(charIDToTypeID("Chnl"), charIDToTypeID("fsel"));
    ADselector.putReference(charIDToTypeID("null"), ARlayerRef);
    ARchannelRef.putEnumerated(charIDToTypeID("Chnl"), charIDToTypeID("Chnl"), charIDToTypeID("Trsp"));
    ADselector.putReference(charIDToTypeID("T   "), ARchannelRef);
    executeAction(charIDToTypeID("setd"), ADselector, DialogModes.NO);

    var frame = {
        left: app.activeDocument.selection.bounds[0] + 2,
        top: app.activeDocument.selection.bounds[1] + 2,
        right: app.activeDocument.selection.bounds[2] - 2,
        bottom: app.activeDocument.selection.bounds[3] - 2
    }
    app.activeDocument.selection.invert();

    var rectangularSelection = [[frame.left, frame.top],
    [frame.left, frame.bottom],
    [frame.right, frame.bottom],
    [frame.right, frame.top]];
    app.activeDocument.selection.select(rectangularSelection, SelectionType.INTERSECT, 0, false);
};

selectInterior();

A PNG image has a single layer  the layer bounds may be smaller then the document canvas for the PNG subject may be boarded by empty pixels.  The bounds or the Png subject is the layers bounds, The bounds is a rectangle that is so many pixels wide and so many  pixel high  that is located somewhere with in the document Canvas. The layer bounds it either Canvas size or smaller.  The PNG subject may has pixels like you Frame or be any shape and have empty pixels like your frame has an empty image area.     You can load the layer transparency as a selection the get the selection bounds it will be the PNG Subject bounds. You frame's rectangle bounds. Image Crop will then crop off the transparent canvas boarders

It seem to me you know nothing about scripting Photoshop.  And you  also do not know how to use Photoshop well or understand how Photoshop works or does things.  What you seem to want to do is frame an image and perhaps mat the image in the frame and  hang the  framed image on a wall.   This is easy to do by expanding  the image's canvas add a Mat layer. Expand the canvas add a frame layer. Expand the canvas and add a wall layer.  This can be done using Photoshop actions and the images used  can even be a High resolution Print size image.  You will be able to learn how to record Actions and play actions.  Photoshop Action are easy to record and use, Actions are just a recorded sequence of Photoshop Steps.  On a document you perform the sequence of steps the action recorder records the steps and you have your action.  There Are additional features you can use that the Action recorder supports.  Photoshop scripting is programming  Photoshop.  Scripts preform Photoshop steps logically.  You need Programming knowledge, know how to use Photoshop well and understand how photoshop works.   Scripting Photoshop is not easy.   Most Photoshop users will never program a Photoshop script. They may use Script provided by Adobe or made available by other Photoshop Script programmers. Here is how Actions may work.