Created attachment 6067 
skip the gdk_pixbuf_loader_new_with_mime_type

Ristretto fails to show pictures where file extension doesnt match the mime type

in ristretto-0.8.0/src/image_viewer.c the following is called

 transaction->loader = gdk_pixbuf_loader_new_with_mime_type (rstto_file_get_content_type (file), NULL); 

it shows an error as the suppled mime type is wrong, glib2s content sniff seems brokken as the file extension gets used.

right after that line we have 

      /* HACK HACK HACK */
     if (transaction->loader == NULL)
     {
          transaction->loader = gdk_pixbuf_loader_new();
     }

Sadly that fails as transaction->loader aint NULL when the error has been show, so we end up with ristretto never showing the picure, eventhough it has showen the thumbnail.

Solution dont call the gdk_pixbuf_loader_new_with_mime_type just go straight to gdk_pixbuf_loader_new_with_mime_type , well easier than trying to fix glib2 anyway.