support compare for ImageMagick

fix tests that fail on Linux

.gitignore

@@ -10,3 +10,4 @@ examples/imgs/*
 !examples/imgs/orientation/*\d.jpg
 !examples/imgs/orientation/*.correct.jpg
 *.sw*
+.idea

index.js

@@ -115,6 +115,7 @@ require("./lib/args")(gm.prototype);
 require("./lib/drawing")(gm.prototype);
 require("./lib/convenience")(gm.prototype);
 require("./lib/command")(gm.prototype);
+require("./lib/compare")(gm.prototype);
 
 /**
  * Expose.
@@ -122,7 +123,7 @@ require("./lib/command")(gm.prototype);
 
 module.exports = exports = gm;
 module.exports.utils = require('./lib/utils');
-module.exports.compare = require('./lib/compare');
+module.exports.compare = require('./lib/compare')();
 module.exports.version = JSON.parse(
   require('fs').readFileSync(__dirname + '/package.json', 'utf8')
 ).version;

lib/compare.js

@@ -18,41 +18,77 @@ var utils = require('./utils');
  * @param {Function} cb(err, Boolean, equality, rawOutput)
  */
 
-module.exports = exports = function compare (orig, compareTo, tolerance, cb) {
-  orig = utils.escape(orig);
-  compareTo = utils.escape(compareTo);
-
-  // outputting the diff image
-  if (typeof tolerance === 'object') {
-    var diffOptions = tolerance;
-    if (typeof diffOptions.file !== 'string') {
-      throw new TypeError('The path for the diff output is invalid');
-    }
-    // graphicsmagick defaults to red
-    var highlightColorOption = diffOptions.highlightColor
-      ? ' -highlight-color ' + diffOptions.highlightColor + ' '
-      : ' ';
+module.exports = exports = function (proto) {
+  function compare(orig, compareTo, tolerance, cb) {
+    orig = utils.escape(orig);
+    compareTo = utils.escape(compareTo);
 
-    return exec('gm compare' + highlightColorOption + orig + ' ' + compareTo +
-      ' -file ' + utils.escape(diffOptions.file), cb);
-  }
+    var isImageMagick = this._options && this._options.imageMagick;
+    var bin = isImageMagick ? '' : 'gm ';
 
-  // else, output the mean square error (mse)
-  if ('function' == typeof tolerance) {
-    cb = tolerance;
-    tolerance = 0.4;
-  }
+    // outputting the diff image
+    if (typeof tolerance === 'object') {
+      var diffOptions = tolerance;
+      if (typeof diffOptions.file !== 'string') {
+        throw new TypeError('The path for the diff output is invalid');
+      }
+      // graphicsmagick defaults to red
+      var highlightColorOption = diffOptions.highlightColor
+        ? ' -highlight-color ' + diffOptions.highlightColor + ' '
+        : ' ';
+      var diffFilename = utils.escape(diffOptions.file);
+      var diffOpt = isImageMagick ? diffFilename : ('-file ' + diffFilename);
+      var cmd = bin + 'compare' + highlightColorOption + orig + ' ' + compareTo +
+        ' ' + diffOpt;
 
-  exec('gm compare -metric mse ' + orig + ' ' + compareTo, function (err, stdout, stderr) {
-    if (err) return cb(err);
+      return exec(cmd, function (err, stdout, stderr) {
+        if (isImageMagick && err && err.code === 1) {
+          err = null;
+        }
+        return cb(err, stdout, stderr);
+      });
+    }
 
-    var match = /Total: (\d+\.?\d*)/m.exec(stdout);
-    if (!match) {
-      err = new Error('Unable to parse output.\nGot ' + stdout);
-      return cb(err);
+    // else, output the mean square error (mse)
+    if ('function' == typeof tolerance) {
+      cb = tolerance;
+      tolerance = 0.4;
     }
 
-    var equality = parseFloat(match[1]);
-    cb(null, equality <= tolerance, equality, stdout);
-  });
-}
+    var execCmd = bin + 'compare -metric mse ' + orig + ' ' + compareTo;
+    // For ImageMagick diff file is required but we don't care about it, so null it out
+    isImageMagick && (execCmd += ' null:');
+
+    exec(execCmd, function (err, stdout, stderr) {
+      // ImageMagick returns err code 2 if err, 0 if similar, 1 if dissimilar
+      if (isImageMagick) {
+        if (!err) {
+          return cb(null, 0 <= tolerance, 0, stdout);
+        }
+        if (err.code === 1) {
+          err = null;
+          stdout = stderr;
+        }
+      }
+      if (err) {
+        return cb(err);
+      }
+      // Since ImageMagick similar gives err code 0 and no stdout, there's really no matching
+      var regex = isImageMagick ? /\((\d+\.?\d*)\)/m : /Total: (\d+\.?\d*)/m;
+      var match = regex.exec(stdout);
+      if (!match) {
+        err = new Error('Unable to parse output.\nGot ' + stdout);
+        return cb(err);
+      }
+
+      var equality = parseFloat(match[1]);
+      cb(null, equality <= tolerance, equality, stdout);
+    });
+  }
+
+  if (proto) {
+    proto.compare = compare;
+  }
+  return compare;
+};
+

test/compareImageMagick.js

@@ -0,0 +1,31 @@
+var assert = require('assert');
+var fs = require('fs');
+
+module.exports = function (gm, dir, finish, GM) {
+
+  // Same image
+  gm.compare(dir + '/original.jpg', dir + '/original.png', function(err, same) {
+    if (err) return finish(err);
+    if (!same) return finish(new Error('Compare should be the same!'));
+
+    // Create a new noisy image
+    gm.noise(0.3).write(dir + '/noise3.png', function (err) {
+      if (err) return finish(err);
+
+      var options = {
+        highlightColor: 'yellow',
+        file: dir + '/diff.png'
+      };
+
+      // Compare these images and write to a file.
+      gm.compare(dir + '/original.jpg', dir + '/noise3.png', options, function(err) {
+        if (err) return finish(err);
+
+        fs.exists(options.file, function(exists) {
+          if (exists) finish();
+          else finish(new Error('Diff file does not exist.'));
+        });
+      });
+    })
+  });
+};