added; subclassing with options

will be used for imagemagick support

index.js

@@ -53,10 +53,37 @@ function gm (source, height, color) {
   this.source = source;
 }
 
+var super = gm;
+gm.subClass =
+gm.setOptions = function subClass (options) {
+  function gm (source, height, color) {
+    if (!(this instanceof super)) {
+      return new gm(source, height, color);
+    }
+
+    super.call(this, source, height, color);
+  }
+
+  gm.prototype.__proto__ = super.prototype;
+  gm.prototype._options = {};
+
+  var keys = Object.keys(options)
+    , i = keys.length
+    , key
+
+  while (i--) {
+    key = keys[i];
+    gm.prototype._options[key] = options[key];
+  }
+
+  return gm;
+}
+
 /**
  * Augment the prototype.
  */
 
+require("./lib/options")(gm.prototype);
 require("./lib/getters")(gm);
 require("./lib/args")(gm.prototype);
 require("./lib/drawing")(gm.prototype);
@@ -67,6 +94,6 @@ require("./lib/command")(gm.prototype);
  * Expose.
  */
 
-module.exports = gm;
+module.exports = exports = gm;
 module.exports.version = "0.6.0";
 

lib/options.js

@@ -0,0 +1,6 @@
+
+// gm - Copyright Aaron Heckmann <aaron.heckmann+github@gmail.com> (MIT Licensed)
+
+module.exports = exports = function (proto) {
+  proto._options = {};
+}

test/subclass.js

@@ -0,0 +1,26 @@
+
+// gm - Copyright Aaron Heckmann <aaron.heckmann+github@gmail.com> (MIT Licensed)
+
+
+var assert = require('assert')
+
+module.exports = function (_, dir, finish, gm) {
+
+  assert.equal('gm', gm('test').constructor.name);
+  assert.equal(undefined, gm.prototype._options.imageMagick);
+
+  var sub = gm.subClass({ imageMagick: true });
+
+  assert.equal('gm', sub('test').constructor.name);
+  assert.equal(true, sub.prototype._options.imageMagick);
+
+  var s = sub('test');
+  assert.equal(true, s._options.imageMagick);
+  assert.equal(undefined, gm.prototype._options.imageMagick);
+
+  gm(dir + '/photo.JPG')
+  .thumb(50, 80, dir + '/SUBthumb.png', function subthumb (err) {
+    if (err) return finish(err);
+    finish();
+  });
+}