CombineImage.js

/**
 * This JXA script combines 2 or more images into one using ImageMagick.
 * 
 * Prerequisite:
 * 1. Mac Yosemite
 * 2. ImageMagick
 * 
 * Steps:
 * 1. Launch Automator app
 * 2. Create an Automator service.
 * 3. Set the input of the service as "image files" in "Finder"
 * 4. Add a "Run JavaScript" task.
 * 5. Paste the following code into the script field.
 * 6. Save the service and give it a name.
 * 
 * How to use:
 * 1. Select some image files in Finder
 * 2. Run the service from the system's Service menu.
 */

var ImageMagickConvert = '/usr/local/bin/convert'; // point this path to the installed location of ImageMagick's convert command
var app = Application.currentApplication();
app.includeStandardAdditions = true;

function alert(text, msg) {
	var options = { };
	if (msg) options.message = msg;
	app.displayAlert(text, options);
}

function run(input, parameters) {

	if (!input || input.length < 2) {
		alert('Please select 2 or more images to combine!');
		return input;
	}
	
	var cmd = ImageMagickConvert;
	var output = null;
	var names = [];
	var dir = null;
	
	input.forEach(function(file){
	   cmd += ' "' + file + '"';
	   
	   // get the file name of the input file and use it for the output file name
	   var pathComponents = file.toString().split('/');
	   var filename = pathComponents.pop().split('.').shift();
	   var dirname = pathComponents.join('/');
	   names.push(filename);
	   
	   // use the first file's directory as the output directory
	   if (!dir) dir = dirname;
	});
	
	// compose the output path
	output = [dir, names.join('+') + '.png'].join('/');
	
	// compose the final command
	cmd += ' +append "' + output + '"';
	
	// execute the command
	app.doShellScript(cmd);

	// return the output to next task
	return Path(output);
}