Lesson #1 after using the iPhone: Automatic Orientation

Remember those days of downloading your photos from your camera, then going through them, one by one… and rotating each picture right-side up until you get drowsy or give up? Such tedious work! Oh, and did you click save after you rotated?

Apparently, pictures taken from the iPhone and many new digital cameras (though none from the world’s largest camera manufacturer) comes embedded with orientation information! To put it simply, it means that these digital photos already know if they are landscape or portrait - How cool is that?

Unfortunately, not all software makes use of this piece of information to save you the labor. And this includes even cool sites like Flickr :-( What a shame. And it doesn’t help that most image upload/resize/crop HOWTOs doesn’t talk about it either.

SharedCopy is cooler than that. Though imaging is not our forte, and its just done for your little profile picture, things are set up such that your profile picture will be right-side up :-D And now, with the help of some monkey-patching, your Rails/Ruby-powered website can be as cool too!

RMagick users, simply include the code below (e.g. append to config/environment.rb):

require 'RMagick' unless defined?(Magick)
Magick::Image.class_eval do
  class << self
    def read_with_auto_upright(*args, &block)
      self.read_without_auto_upright(*args, &block).collect do |img|
          # if there's nothing to rotate, auto_orient! will return nil
          img.auto_orient! || img
        rescue NotImplementedError
          # Older versions of ImageMagick has no auto_orient!
          case img.get_exif_by_entry("Orientation") && img["EXIF:Orientation"]
          # img["EXIF:Orientation"] might not be ready until get_exif_by_entry() is called
          when "6"
            # Magick::RightTopOrientation
            img["EXIF:Orientation"] = "1"
          when "3"
            # Magick::BottomRightOrientation
            img["EXIF:Orientation"] = "1"
          when "8"
            # Magick::LeftBottomOrientation
            img["EXIF:Orientation"] = "1"

    # wrap around RMagick::Image#read method so that
    # any images loaded in memory are already upright
    alias :read_without_auto_upright :read
    alias :read :read_with_auto_upright
    # note: not using alias_method_chain so that this
    #       snippet can be used outside of Rails

  ImageScience users, if you trust my C++ code, just place this patched image_science.rb in your vendor/ directory. Otherwise you can apply this patch manually:

--- lib/image_science.rb	2007-10-16 12:11:08.000000000 +0800
+++ lib/image_science.rb.new 2007-10-16 12:11:01.000000000 +0800
@@ -150,6 +150,21 @@
           VALUE result = Qnil;
           int flags = fif == FIF_JPEG ? JPEG_ACCURATE : 0;
           if (bitmap = FreeImage_Load(fif, input, flags)) {
+            FITAG *tagValue = NULL;
+            FreeImage_GetMetadata(FIMD_EXIF_MAIN, bitmap, "Orientation", &tagValue);
+            switch (tagValue == NULL ? 0 : *((short *) FreeImage_GetTagValue(tagValue))) {
+              case 6:
+                bitmap = FreeImage_RotateClassic(bitmap, 270);
+                break;
+              case 3:
+                bitmap = FreeImage_RotateClassic(bitmap, 180);
+                break;
+              case 8:
+                bitmap = FreeImage_RotateClassic(bitmap, 90);
+                break;
+              default:
+               break;
+            }
             result = wrap_and_yield(bitmap, self, fif);
           return result;

What’s done here (for both) is that images loaded into memory will be checked for orientation information and have its orientation corrected if possible (otherwise its left untouched). In memory. So all your image operations like "width", "resize" will be magically "correct".

No modifications required to your routine. Heck, you can even pretend the whole scenario never existed!