terom@120: """
terom@120:     The various Exif backends that we have
terom@120: """
terom@120: 
terom@120: from __future__ import with_statement
terom@120: 
terom@120: import utils
terom@120: 
terom@122: MIRROR_NONE         = 0
terom@122: MIRROR_HORIZONTAL   = 1
terom@122: MIRROR_VERTICAL     = 2
terom@122: 
terom@122: ROTATE_NONE         = 0
terom@122: ROTATE_90           = 90
terom@122: ROTATE_180          = 180
terom@122: ROTATE_270          = 270
terom@122: 
terom@120: class ExifHandler (object) :
terom@120:     """
terom@120:         Our generic interface for Exif data
terom@120:     """
terom@120: 
terom@120:     def __init__ (self, file) :
terom@120:         """
terom@120:             Load Exif data from the given File.
terom@120:         """
terom@120: 
terom@120:         self.file = file
terom@120:     
terom@122:     def image_tag_value (self, tag, default=None) :
terom@122:         """
terom@122:             Load and return the raw binary value for the given main image tag.
terom@122:         """
terom@122: 
terom@122:         return default
terom@122: 
terom@120:     def image_tag (self, tag, default=None) :
terom@120:         """
terom@120:             Load and return the human-readable unicode-safe value for the given main image tag.
terom@120:         """
terom@120: 
terom@122:         return default
terom@120: 
terom@120:     def image_tags (self, tags) :
terom@120:         """
terom@120:             Load and return the given tags for the main image as a sequence of (tag, value) tuples , following the same
terom@120:             rules as image_tag, except there should mainly be only one call to this function, encompassing all the
terom@120:             relevant tags.
terom@120: 
terom@120:             The returned list should omit those values which were not found.
terom@120:         """
terom@120:     
terom@120:         for tag in tags :
terom@120:             # try and fetch value
terom@120:             value = self.image_tag(tag)
terom@120: 
terom@120:             # filter out default not-found
terom@120:             if value is not None :
terom@120:                 yield tag, value
terom@122:     
terom@122: 
terom@122:     def get_orientation (self) :
terom@122:         """
terom@122:             Get the orientation of the image in terms of mirroring and rotation in integer degrees clockwise.
terom@122:             
terom@122:             Returns a (MIRROR_*, ROTATE_*) tuple, or None if the Orientation tag could not be found.
terom@122: 
terom@122:             Returns None if it could not be found.
terom@122:         """
terom@122:         
terom@122:         # load value
terom@122:         orientation = self.image_tag_value('Orientation')
terom@122: 
terom@122:         # map to tuple or None
terom@122:         # XXX: these are from EXIFpy, verify
terom@122:         return {
terom@122:             1:  (MIRROR_NONE,       ROTATE_NONE ),  # Horizontal (normal)
terom@122:             2:  (MIRROR_HORIZONTAL, ROTATE_NONE ),  # Mirrored horizontal
terom@122:             3:  (MIRROR_NONE,       ROTATE_180  ),  # Rotated 180
terom@122:             4:  (MIRROR_VERTICAL,   ROTATE_NONE ),  # Mirrored vertical
terom@122:             5:  (MIRROR_HORIZONTAL, ROTATE_270  ),  # Mirrored horizontal then rotated 90 CCW
terom@122:             6:  (MIRROR_NONE,       ROTATE_90   ),  # Rotated 90 CW
terom@122:             7:  (MIRROR_HORIZONTAL, ROTATE_90   ),  # Mirrored horizontal then rotated 90 CW
terom@122:             8:  (MIRROR_NONE,       ROTATE_270  ),  # Rotated 90 CCW
terom@122:         }.get(orientation, None)
terom@120: 
terom@120: try :
terom@120:     import pyexiv2
terom@120: 
terom@120: except ImportError :
terom@120:     PyExiv2_Handler = None
terom@120: 
terom@120: else :
terom@120:     class PyExiv2_Handler (ExifHandler) :
terom@120:         NAME = 'pyexiv2'
terom@120: 
terom@120:         def __init__ (self, file) :
terom@120:             """
terom@120:                 Load as pyexiv2.Image
terom@120:             """
terom@120:             
terom@120:             # create
terom@120:             self.image = pyexiv2.Image(file.path)
terom@120: 
terom@120:             # load
terom@120:             self.image.readMetadata()
terom@120:         
terom@122:         def image_tag_value (self, tag, default=None) :
terom@122:             # try with likely prefixes
terom@122:             for prefix in ('Exif.Photo', 'Exif.Image') :
terom@122:                 try :
terom@122:                     return self.image["%s.%s" % (prefix, tag)]
terom@122:                 
terom@122:                 except (IndexError, KeyError) :
terom@122:                     # nope...
terom@122:                     continue
terom@122: 
terom@122:             else :
terom@122:                 # not ofund
terom@122:                 return default
terom@122: 
terom@120:         def image_tag (self, tag, default=None) :
terom@121:             # try with likely prefixes
terom@121:             for prefix in ('Exif.Photo', 'Exif.Image') :
terom@121:                 try :
terom@121:                     return self.image.interpretedExifValue("%s.%s" % (prefix, tag))
terom@121:                 
terom@121:                 except (IndexError, KeyError) :
terom@121:                     # nope...
terom@121:                     continue
terom@121: 
terom@121:             else :
terom@121:                 # not ofund
terom@120:                 return default
terom@120:     
terom@120: try :
terom@120:     from lib import EXIF
terom@120: 
terom@120: except ImportError :
terom@120:     EXIF_Handler = None
terom@120: 
terom@120: else :
terom@120:     class EXIF_Handler (ExifHandler) :
terom@120:         NAME = 'EXIFpy'
terom@120: 
terom@120:         def __init__ (self, file) :
terom@120:             """
terom@120:                 Load using EXIF.process_file
terom@120:             """
terom@120:             
terom@120:             with file.open('rb') as fh :
terom@120:                 self.tags = EXIF.process_file(fh)
terom@120:         
terom@120:         def image_tag (self, tag, default=None) :
terom@121:             # try with likely prefixes
terom@121:             for prefix in ('Image', 'EXIF') :
terom@121:                 name = prefix + ' ' + tag
terom@121: 
terom@121:                 if name in self.tags :
terom@121:                     return self.tags[name]
terom@121: 
terom@121:             else :
terom@121:                 # not found
terom@121:                 return default
terom@120: 
terom@120: # ExifHandler implementations to use, in preference order
terom@120: EXIF_HANDLERS = [
terom@120:     # reasonably fast, but requires the native library and extension module
terom@120:     PyExiv2_Handler,
terom@120: 
terom@120:     # pure-python, but very, very slow
terom@120:     EXIF_Handler,
terom@120: ]
terom@120: 
terom@120: # default ExifHandler to use
terom@120: EXIF_HANDLER = utils.first(EXIF_HANDLERS)
terom@120: 
terom@120: # ExifHandler implementations by name
terom@130: EXIF_HANDLERS_BY_NAME = dict((h.NAME, h) for h in EXIF_HANDLERS if h)
terom@120: 
terom@120: def load (config, file) :
terom@120:     """
terom@120:         Load Exif data using the configured Exif handler, and return the instance.
terom@120: 
terom@120:         Returns None if there wasn't any Exif handler available for use.
terom@120:     """
terom@120: 
terom@120:     if config.exif_handler :
terom@120:         # explicit
terom@120:         exif_handler = config.exif_handler
terom@120: 
terom@120:     elif config.exif_handler_name :
terom@120:         # by name
terom@120:         exif_handler = EXIF_HANDLERS_BY_NAME[config.exif_handler_name]
terom@120: 
terom@120:     else :
terom@120:         # default
terom@120:         exif_handler = EXIF_HANDLER
terom@120:     
terom@120:     if exif_handler :
terom@120:         # found one, use it
terom@120:         return exif_handler(file)
terom@120: 
terom@120:     else :
terom@120:         # nothing :(
terom@120:         return None
terom@120: