Need Action That Makes an Equal-Sized Border for Images With Different Sizes

OK, here is that script that I was working on. It grew a little bit once I started the conditional check for a flattened or layered original, then I had to refactor and optimise the code etc.

It uses the document's width to base the border % size on. It is easy enough to change this to the doc's height (line 63), see the comments in the file.

Please let me know how it goes. 

This script uses some GUI input to set colour and border size, it could be adjusted for use with batching.

/*

Extend Canvas Border by Percentage of Doc Width.jsx
Version 1.0
Stephen Marsh - 2021

Need Action That Makes an Equal-Sized Border for Images With Different Sizes
https://community.adobe.com/t5/photoshop/need-action-that-makes-an-equal-sized-border-for-images-with-different-sizes/td-p/11876979

Action that uses a percentage of image size in pixel dimensions
https://community.adobe.com/t5/photoshop/action-that-uses-a-percentage-of-image-size-in-pixel-dimensions/m-p/9897687

You can change the docWidth.value to docHeight.value for the basis of the frame size on line 63

*/

#target photoshop
app.bringToFront();

// Conditional Background layer check
if (app.activeDocument.activeLayer.isBackgroundLayer) {
    setForeground();
    addBorder();
}
// Otherwise run on layered files
else {
    addBorder();
    addColorFillLayer();
    // "previous" or "next" or "front" or "back"
    moveLayerRelativeStack("back");
}

function addBorder() {

    // Save the current ruler units and set to pixels
    var savedRuler = app.preferences.rulerUnits;
    app.preferences.rulerUnits = Units.PIXELS;

    // Loop the input prompt until a number is entered
    var origInput;
    while (isNaN(origInput = prompt("Enter the border size" + "\n" + "(based on a % of the document's width)", "4")));

    // Test if cancel returns null, then terminate the script
    if (origInput === null) {
        alert('Script cancelled!');
        return
    }

    // Test if an empty string is returned, then terminate the script
    if (origInput === "") {
        alert('A value was not entered, script cancelled!');
        return
    }

    // Convert decimal input to integer
    var borderSize = parseInt(origInput);

    // Border size value in pixels
    var doc = app.activeDocument;
    var docWidth = doc.width;
    var docHeight = doc.height;
    // Change the docWidth.value to docHeight.value for the basis of the frame size
    var canvasExtension = borderSize / 100 * docWidth.value;

    // Resize canvas - relative width & height
    extendCanvasRelative(true, canvasExtension, canvasExtension);

    function extendCanvasRelative(relative, width, height) {
        var c2t = function (s) {
            return app.charIDToTypeID(s);
        };
        var s2t = function (s) {
            return app.stringIDToTypeID(s);
        };
        var descriptor = new ActionDescriptor();
        descriptor.putBoolean(s2t("relative"), relative);
        descriptor.putUnitDouble(s2t("width"), s2t("pixelsUnit"), width);
        descriptor.putUnitDouble(s2t("height"), s2t("pixelsUnit"), height);
        descriptor.putEnumerated(s2t("horizontal"), s2t("horizontalLocation"), c2t("Cntr"));
        descriptor.putEnumerated(s2t("vertical"), s2t("verticalLocation"), c2t("Cntr"));
        descriptor.putEnumerated(s2t("canvasExtensionColorType"), s2t("canvasExtensionColorType"), s2t("foregroundColor"));
        executeAction(s2t("canvasSize"), descriptor, DialogModes.NO);
    }

    // Restore the ruler units
    app.preferences.rulerUnits = savedRuler;

}

function addColorFillLayer() {

    getColorpickerColor();

    var fColor = app.foregroundColor;
    var R = fColor.rgb.red.toFixed(2);
    var G = fColor.rgb.green.toFixed(2);
    var B = fColor.rgb.blue.toFixed(2);

    makeFill(R, G, B);

    function makeFill(red, Grn, blue) {
        var c2t = function (s) {
            return app.charIDToTypeID(s);
        };
        var s2t = function (s) {
            return app.stringIDToTypeID(s);
        };
        var descriptor = new ActionDescriptor();
        var descriptor2 = new ActionDescriptor();
        var descriptor3 = new ActionDescriptor();
        var descriptor4 = new ActionDescriptor();
        var reference = new ActionReference();
        reference.putClass(s2t("contentLayer"));
        descriptor.putReference(c2t("null"), reference);
        descriptor4.putDouble(s2t("red"), red);
        descriptor4.putDouble(c2t("Grn "), Grn);
        descriptor4.putDouble(s2t("blue"), blue);
        descriptor3.putObject(s2t("color"), s2t("RGBColor"), descriptor4);
        descriptor2.putObject(s2t("type"), s2t("solidColorLayer"), descriptor3);
        descriptor.putObject(s2t("using"), s2t("contentLayer"), descriptor2);
        executeAction(s2t("make"), descriptor, DialogModes.NO);
    }

    function getColorpickerColor() {
        if (app.showColorPicker()) {
            return app.foregroundColor;
        } else {
            return false;
        }
    }
}

function moveLayerRelativeStack(relPos) {
    var c2t = function (s) {
        return app.charIDToTypeID(s);
    };
    var s2t = function (s) {
        return app.stringIDToTypeID(s);
    };
    var descriptor = new ActionDescriptor();
    var reference = new ActionReference();
    var reference2 = new ActionReference();
    reference.putEnumerated(s2t("layer"), s2t("ordinal"), s2t("targetEnum"));
    descriptor.putReference(c2t("null"), reference);
    reference2.putEnumerated(s2t("layer"), s2t("ordinal"), s2t(relPos));
    descriptor.putReference(s2t("to"), reference2);
    executeAction(s2t("move"), descriptor, DialogModes.NO);
}

function setForeground() {

    var fColor = app.foregroundColor;
    var R = fColor.rgb.red.toFixed(2);
    var G = fColor.rgb.green.toFixed(2);
    var B = fColor.rgb.blue.toFixed(2);

    getColorpickerColor();

    function getColorpickerColor() {
        if (app.showColorPicker()) {
            return app.foregroundColor;
        } else {
            return false;
        }
    }
}

https://prepression.blogspot.com/2017/11/downloading-and-installing-adobe-scripts.html

The action mentioned in that thread will create an even horizontal/vertical sized border inside the image. Is this what you need help recreating? A 1000px width document with a 4% border based on the width would end up with a visible area of 920px on the width. This will cover existing content with the border.

The alternative would be a document that was 1080px on the width, extending the canvas and not covering exising content.