Generating Large Image Grids in Photoshop using Javascript

grid.jsx

var shuffleAndValidateFiles = function(files) {
	var F = new Array();
	while (files.length > 0) {
		var N = Math.floor(Math.random()*files.length);

		if ((files[N] instanceof File) && !files[N].hidden) {
			F.push(files[N]);
		}

		files.splice(N,1);
	}
	return F;
}

preferences.rulerUnits = Units.PIXELS;
var SEARCH_MASK = "*.jpg";
var PROMPT_TEXT = "Select a folder";

try {
	var folder = Folder.selectDialog(PROMPT_TEXT);
	if (folder == null) {
		throw "noInput";
	}
	var files = folder.getFiles(SEARCH_MASK);

	files = shuffleAndValidateFiles(files);
} catch (exception) {
	alert(exception);
}

//Output settings: how many images to output, and the size of each item on the grid in pixels
var total = files.length;
var gridCols = prompt("How many columns would you like your grid to be?", "4");
var gridRows = Math.max(Math.floor(total / gridCols), 1);
var sqWidth = parseInt(prompt("How wide would you like each image to be?", "300"), 10);
var sqHeight = parseInt(prompt("How tall would you like each image to be?", "300"), 10);

if (confirm(
	"About to create a "+gridRows+" * "+gridCols+
	" grid that is "+(gridRows*sqWidth)+"px * "+(gridCols*sqHeight)+"px large. "+
	"There'll be a total of "+total+" images. Is that ok?")) {

	var doc = app.documents.add(sqWidth*gridCols+"px", sqHeight*gridRows+"px", 300, "Generated Grid");

	var cropCurrentToFit = function(newWidth, newHeight) {
		var docRef = app.activeDocument;
		var w = parseInt(docRef.width, 10);
		var h = parseInt(docRef.height, 10);
		var portrait = h > w;

		var scale = Math.min(w/newWidth, h/newHeight);

		var x1, x2, xo, y1, y2, yo;
		x1 = x2 = w*0.5;
		xo = scale*newWidth;
		x1 += xo*0.5; x2 -= xo*0.5;

		y1 = y2 = h*0.5;
		yo = scale*newHeight;
		y1 += yo*0.5; y2 -= yo*0.5;

		var bounds = [x2, y2, x1, y1];
		docRef.crop(bounds, null, newWidth, newHeight);
		return docRef;
	}

	var row = function(y) {
		for (var x = 0; x < gridCols; x++) {
			var i = (y*gridCols + x) % files.length;
			open(files[i]);

			var currentDoc = cropCurrentToFit(sqWidth, sqHeight);
			currentDoc.selection.selectAll();
			currentDoc.selection.copy();
			currentDoc.close(SaveOptions.DONOTSAVECHANGES);

			app.activeDocument = doc;
			var xpixel = sqWidth * x;
			var ypixel = sqHeight * y;


			doc.selection.select([
				[ xpixel, ypixel ], //TOP LEFT
				[ xpixel + sqWidth, ypixel ], //TOP RIGHT
				[ xpixel + sqWidth, ypixel + sqHeight ], //BOTTOM RIGHT
				[ xpixel, ypixel + sqHeight ] //BOTTOM LEFT
			]);
			doc.paste(true);
			doc.selection.deselect();

			if (i % 10 == 9) { doc.flatten(); }
		}
	}

	var grid = function() {
		for (var y = 0; y < gridRows || y < 1; y++) {
			doc.suspendHistory('Alert', "row("+y+")");
		}
		doc.flatten();
	}

	doc.suspendHistory("Grid Generation", "grid();");
}

/*
	doc.suspendHistory() is used to lower memory usage.

	Storing every change to the image can get tiresome for all but the best computers,
	so instead this script "forgets" past actions after completing each row. The whole
	process is merged into one action at the end of the script.
*/