Proportional image resize script for Photoshop in Adobe's weird proprietary JavaScript extension as ported from PHP (god help us all).

imageResize.jsx

#target photoshop

var destHeight = 800
var destWidth = 800

function resize (sourceDoc,dest_w,dest_h) {
	var source_w = sourceDoc.width.as("px")
	var source_h = sourceDoc.height.as("px")

	if (dest_w == 0 && dest_h != 0) {
		dest_w = (dest_h/source_h)*source_w;
	}
	else if (dest_h == 0 && dest_w != 0) {
		dest_h = (dest_w/source_w)*source_h;
	}
	else if (dest_h == 0 && dest_w == 0) {
		return sourceDoc;
	}

	sourceDoc.resizeImage(UnitValue(dest_w,"px"),UnitValue(dest_h,"px"),72,ResampleMethod.BICUBIC)
	return sourceDoc
}

function maxsize (sourceDoc,dest_w,dest_h) {
	var source_w = sourceDoc.width.as("px")
	var source_h = sourceDoc.height.as("px")

	if (source_w <= dest_w) {
		dest_w = 0;
	}
	if (source_h <= dest_h) {
		dest_h = 0;
	}
	if (dest_w != 0 && dest_h != 0) {
		if ((dest_h/source_h) < (dest_w/source_w)) {
			dest_w = 0;
		}
		else {
			dest_h = 0;
		}
	}

	return resize(sourceDoc,dest_w,dest_h);
}

Array.prototype.inArray = function (value) {
	var i;
	for (i=0; i < this.length; i++) {
	if (this[i] === value) {
	return true;
	}
	}
	return false;
};

var sourceFolder = Folder.selectDialog("Choose a folder:")

if (sourceFolder != null) {
	var sourceFiles = sourceFolder.getFiles()

	var exportWebOptions = ExportOptionsSaveForWeb
	exportWebOptions.format = SaveDocumentType.JPEG
	exportWebOptions.quality = 85

	var destFolder = sourceFolder
	destFolder.changePath("./processed/")
	destFolder.create()

	for (i in sourceFiles) {
		var extension = sourceFiles[i].name.split(".").pop().toLowerCase()
		if (sourceFiles[i].name != "." && sourceFiles[i].name != ".." && (extension == "tiff" || extension == "tif" || extension == "jpg" || extension == "psd")) {
			var sourceDoc = app.open(sourceFiles[i])

			var sourceHeight = sourceDoc.height.as("px")
			var sourceWidth = sourceDoc.width.as("px")

			sourceDoc = maxsize(sourceDoc,destWidth,destHeight)

			var destFile = File(destFolder.fullName + "/" + sourceFiles[i].name.split(".")[0] + ".jpg")
			sourceDoc.exportDocument(destFile,ExportType.SAVEFORWEB,exportWebOptions)
			sourceDoc.close(SaveOptions.DONOTSAVECHANGES)
		}
	}
}