[Mono-dev] Reading Exif Data with System.Drawing or Gtk#

[Patrick Kowalzick]

Dear List,

I am reading exif-data from jpegs (mainly thumb and orientation) using 
System.Drawing. Something like:

string orientation = null;
using (FileStream fs = new FileStream(path,FileMode.Open))
    using (Image img = Image.FromStream(fs,true,false))
       foreach (PropertyItem pi in img.PropertyItems)
          if (pi.Id == 274)
          {
             orientation =
                BitConverter.ToInt16(pi.Value,0).ToString();
                break;
          }

Important here is the third parameter from Image.FromStream 
(validateImageData), which should supress loading the complete 
image-file, if you access exif data only.

This works fine for MS.net, but mono (2.6 on Ubuntu) reads the complete 
image. See as well:

http://tinyurl.com/39jymfs
"# Status: TODO
# Comment: useEmbeddedColorManagement and validateImageData aren't 
supported."

As a result, there are massive performance differences between MS.net 
and mono :(.

So I am looking for alternatives to just read exif data from images, if 
possible without including third party libraries (maybe taglib# with 
picture support). I am already using GTK#, so this would be the best 
solution for me.

What I found so far:

-System.Windows.Media.Imaging.BitmapSource is not yet included in mono, 
and will not in mono 2.8(?).

-Gdk.Pixbuf Solution, but just for reading orientation:
    Gdk.Pixbuf icon = new Gdk.Pixbuf(path);
    string orientation = icon.GetOption("orientation");
Same behaviour: needs to load image first, and I do not find any 
information, which options I could retrieve via "GetOption".


Does anyone has a pointer for me, where to search for more information, 
or how to read Exif Data using Gtk?

Kind regards,
Patrick