Photoshop Javascript: Delete corners of an image

I've continued working and have managed to pull together a functioning solution BUT it is very, very slow.

Code below is my proof of concept that works on one corner only, and it takes 50 seconds to run (Windows machine, very old but high spec).

It also relies on two pixel arrays - the first is for deleting (cutting) pixels entirely (that part of the code is fast) and the second array is for changing the opacity of individual pixels - i.e. feathering (this is the slow part of the code).

It works on the active document if anyone wants to try it. I might build this out (add the other 3 corners) but with a run time of 3.5 minutes per image I wonder how realistic it really is. It might be better if I use some external source... maybe invoke an Actions (.atn) file from my main script, to add a layer mask and a rectangle with rounded corners, etc. But I'm trying to keep everything as portable as possible, for users.

//-------------------------------------------------------------------------------------
//Cut pixels that can be fully deleted:

//Array of pixels to cut:
//0 = x position
//1 = y position
//2 = x runlength, for efficiency
var cutPixels = [
		[0, 0, 17],
		[0, 1, 14],
		[0, 2, 12],
		[0, 3, 10],
		[0, 4, 9],
		[0, 5, 7],
		[0, 6, 6],
		[0, 7, 5],
		[0, 8, 4],
		[0, 9, 4],
		[0, 10, 3],
		[0, 11, 2],
		[0, 12, 2],
		[0, 13, 1],
		[0, 14, 1],
		[0, 15, 0],
		[0, 16, 0],
		[0, 17, 0],
];

docRef = app.activeDocument;		

//Layer from background:
docRef.activeLayer.isBackgroundLayer = false;


//(topleft, bottomleft, bottomright, topright)
//var shapeRef = [ [10,10], [10,90], [90,90], [90,10] ];
//docRef.selection.select(shapeRef);

for(var p = 0; p < cutPixels.length; p++) {
	docRef.selection.select([ [cutPixels[p][0],cutPixels[p][1]],
							  [cutPixels[p][0],cutPixels[p][1]+1],
							  [cutPixels[p][0]+1+cutPixels[p][2],cutPixels[p][1]+1],
							  [cutPixels[p][0]+1+cutPixels[p][2],cutPixels[p][1]] ],
							  SelectionType.EXTEND);

};

docRef.selection.cut();

//End of cut pixels
//-------------------------------------------------------------------------------------
//Change opacity of softener pixels:

//Array of pixels to change opacity:
//0 = x position
//1 = y position
//2 = opacity
var opacityPixels = [
	[18, 0, 20],[19, 0, 40],[20, 0, 55],[21, 0, 70],[22, 0, 80],[23, 0, 90],
	[15, 1, 20],[16, 1, 50],[17, 1, 75],
	[13, 2, 30],[14, 2, 60],[15, 2, 95],
	[11, 3, 20],[12, 3, 60],[13, 3, 95],
	[10, 4, 40],[11, 4, 80],
	[8, 5, 15],[9, 5, 55],
	[7, 6, 15],[8, 6, 65],
	[6, 7, 15],[7, 7, 65],
	[5, 8, 15],[6, 8, 65],
	[5, 9, 55],
	[4, 10, 40],
	[3, 11, 20],[4, 11, 80],
	[3, 12, 60],
	[2, 13, 30],[3, 13, 95],
	[2, 14, 65],
	[1, 15, 25],[2, 15, 95],
	[1, 16, 50],
	[1, 17, 75],
	[0, 18, 20],
	[0, 19, 40],
	[0, 20, 55],
	[0, 21, 70],
	[0, 22, 80],
	[0, 23, 90]
];

var selRegion, cornerSize = 1;  // size of corner to select

for(var p = 0; p < opacityPixels.length; p++) {
	docRef.selection.select([ [opacityPixels[p][0],opacityPixels[p][1]],
							  [opacityPixels[p][0],opacityPixels[p][1]+1],
							  [opacityPixels[p][0]+1,opacityPixels[p][1]+1],
							  [opacityPixels[p][0]+1,opacityPixels[p][1]] ],
							  SelectionType.EXTEND);

	// Create a temporary document to sample color
	var tempDoc = app.documents.add(cornerSize, cornerSize, 72.0, "temp", NewDocumentMode.RGB, DocumentFill.TRANSPARENT);
	app.activeDocument = docRef; // Switch back to the original document
	docRef.selection.copy(); // Copy the selection

	app.activeDocument = tempDoc; // Switch to the temporary document
	tempDoc.paste(); // Paste the copied selection

			//Sample the pixel color of the top left pixel (i.e. the only one...)
			//https://stackoverflow.com/a/48192241
			// Add a Color Sampler at a given x and y coordinate in the image.
			var pointSample = tempDoc.colorSamplers.add([0,0]);

			// Obtain array of RGB values.
			var rgb = [
				pointSample.color.rgb.red,
				pointSample.color.rgb.green,
				pointSample.color.rgb.blue
			];
			
			app.foregroundColor.rgb.red = rgb[0];
			app.foregroundColor.rgb.green = rgb[1];
			app.foregroundColor.rgb.blue = rgb[2];
			

	// Switch back to original document and delete temp
	app.activeDocument = docRef;
	tempDoc.close(SaveOptions.DONOTSAVECHANGES);

	var newLayer = docRef.artLayers.add(); // Add a new layer
	docRef.selection.fill(app.foregroundColor, ColorBlendMode.NORMAL, 100); // Fill with the foreground color
	newLayer.opacity = opacityPixels[p][2]; // Set the layer opacity

	docRef.activeLayer = docRef.artLayers[1]; // Switch to original layer
	docRef.selection.clear(); // Clear the selected pixel
	docRef.selection.deselect();

	docRef.activeLayer = newLayer; // Switch back to new layer
	// Merge the new layer with the previous layer
	newLayer.merge();

};

//End of change opacity
//-------------------------------------------------------------------------------------

Why don’t you just use the Rectangle Tool to create a Vector Mask and set the Corner Radius in the Options Bar?