morph.js

// gm - Copyright Aaron Heckmann <aaron.heckmann+github@gmail.com> (MIT Licensed)

/**
 * Module dependencies.
 */

var fs = require('fs');

/**
 * Extend proto.
 */

module.exports = function (proto) {

  /**
   * Do nothing.
   */

  function noop () {}

  // http://www.graphicsmagick.org/GraphicsMagick.html#details-morph
  proto.morph = function morph (other, outname, callback) {
    if (!callback) callback = noop;

    if (!outname) {
      throw new Error("an output filename is required");
    }

    var self = this;

    self.out(other, "-morph", 1);

    self.write(outname, function (err, stdout, stderr, cmd) {
      if (err) {
        return callback.call(self, err, stdout, stderr, cmd);
      }

      var remaining = 3;

      fs.unlink(outname + ".0", next);
      fs.unlink(outname + ".2", next);
      fs.rename(outname + ".1", outname, next);

      function next (err) {
        if (next.err) return;

        if (err) {
          next.err = err;
          return callback.call(self, err, stdout, stderr, cmd);
        }

        if (--remaining) return;

        callback.call(self, err, stdout, stderr, cmd);
      }
    });

    return self;
  }
}