add 'orientation' to getters, and autoOrient convenience method for fixing rotation from EXIF metadata

.gitignore

@@ -3,6 +3,7 @@ examples/imgs/*
 !examples/imgs/original.jpg
 !examples/imgs/original.png
 !examples/imgs/original.gif
+!examples/imgs/originalSideways.jpg
 !examples/imgs/morpher.jpg
 *.swp
 *.swo

README.md

@@ -142,6 +142,7 @@ or clone the repo:
 
   - getters
     - [size](http://aheckmann.github.com/gm/#getters) - returns the size (WxH) of the image
+    - orientation - returns the EXIF orientation of the image
     - [format](http://aheckmann.github.com/gm/#getters) - returns the image format (gif, jpeg, png, etc)
     - [depth](http://aheckmann.github.com/gm/#getters) - returns the image color depth 
     - [color](http://aheckmann.github.com/gm/#getters) - returns the number of colors
@@ -151,6 +152,7 @@ or clone the repo:
 
   - manipulation
     - [antialias](http://aheckmann.github.com/gm/#antialias)
+    - autoOrient
     - [bitdepth](http://aheckmann.github.com/gm/#bitdepth)
     - [blur](http://aheckmann.github.com/gm/#blur)
     - [charcoal](http://aheckmann.github.com/gm/#charcoal)

lib/convenience.js

@@ -9,4 +9,5 @@ module.exports = function (proto) {
   require("./convenience/thumb")(proto);
   require("./convenience/morph")(proto);
   require("./convenience/sepia")(proto);
+  require("./convenience/autoOrient")(proto);
 }

lib/convenience/autoOrient.js

@@ -0,0 +1,48 @@
+
+// gm - Copyright Aaron Heckmann <aaron.heckmann+github@gmail.com> (MIT Licensed)
+
+/**
+ * Extend proto.
+ */
+
+module.exports = function (proto) {
+
+  var exifTransforms = {
+    topleft:     ''
+  , topright:    ['-flip', 'horizontal']
+  , bottomright: ['-rotate', 180]
+  , bottomleft:  ['-flip', 'vertical' ]
+  , lefttop:     ['-transpose']
+  , righttop:    ['-rotate', 90]
+  , rightbottom: ['-transverse']
+  , leftbottom:  ['-rotate', 270]
+  }
+
+  proto.autoOrient = function autoOrient () {
+    var self = this;
+    self.preProcess(function(callback) {
+      self.orientation(function (err, orientation) {
+        if (err) return callback(err);
+
+        var transforms = exifTransforms[orientation.toLowerCase()];
+        if(transforms) {
+
+          // remove any existing transforms that might conflict
+          var index = self._out.indexOf(transforms[0]);
+          if (~index) {
+            self._out.splice(index, transforms.length);
+          }
+
+          self.out.apply(self, transforms);
+
+          // strip EXIF profile since we can't reset Orientation=1
+          self.noProfile();
+        }
+
+        callback(self);
+      });
+    });
+
+    return self;
+  }
+}

lib/getters.js

@@ -7,7 +7,7 @@
 
 module.exports = function (proto) {
 
-;['size', 'format', 'depth', 'color', 'res', 'filesize'].forEach(function (getter) {
+;['size', 'orientation', 'format', 'depth', 'color', 'res', 'filesize'].forEach(function (getter) {
 
   proto[getter] = function (opts, callback) {
     if (!callback) callback = opts, opts = {};
@@ -54,7 +54,7 @@ proto.identify = function identify (opts, callback) {
 
   var args = ['identify', '-ping', '-verbose', self.sourceStream ? '-' : self.source];
 
-  self._exec("gm", args, function (err, stdout, stderr) {
+  self._exec("gm", args, function (err, stdout, stderr, cmd) {
     if (err) {
       return callback.call(self, err, stdout, stderr, cmd);
     }
@@ -79,6 +79,10 @@ proto.identify = function identify (opts, callback) {
       }
     };
 
+    handle.Orientation = function Orientation (val) {
+      data.orientation = val;
+    };
+
     handle.Format = function Format (val) {
       data.format = val.split(" ")[0];
     };

test/autoOrient.js

@@ -0,0 +1,13 @@
+
+// gm - Copyright Aaron Heckmann <aaron.heckmann+github@gmail.com> (MIT Licensed)
+
+module.exports = function (_, dir, finish, gm) {
+
+  // this image is sideways, but may be auto-oriented by modern OS's
+  // try opening it in a browser to see its true orientation
+  gm(dir + '/originalSideways.jpg')
+  .autoOrient()
+  .write(dir + '/autoOrient.jpg', function autoOrient (err) {
+    finish(err);
+  });
+}