def __init__(self, parent, br=None):
self.parent = parent
self.br = br
self.tags = TiffTags()
self.tag = None
self.type = None
self.count = None
self.offset = None
self.directory = None
if br:
self._load()
class TiffDirectoryEntry(object):
# XXX Tiff 3.0 types, 6.0 has more, but I don't need them yet
BYTE = 1
ASCII = 2
SHORT = 3
LONG = 4
RATIONAL = 5
STRING = 0
LENGTH = 1
FORMAT = 2
types = {
BYTE: ("byte", 1, "s"),
ASCII: ("ascii", 1, "s"),
SHORT: ("short", 2, "H"),
LONG: ("long", 4, "L"),
RATIONAL: ("rational", 8, "LL"),
}
def __init__(self, parent, br=None):
self.parent = parent
self.br = br
self.tags = TiffTags()
self.tag = None
self.type = None
self.count = None
self.offset = None
self.directory = None
if br:
self._load()
def __repr__(self):
return "TiffDirectoryEntry(parent={}, tag={}, type={}, count={}, offset={})".format(
self.parent.offset, self._tagstr(self.tag), self._typestr(self.type), self.count, self.offset
)
def __str__(self):
return self.__repr__()
def _typestr(self, type):
if type in self.types:
return self.types[type][self.STRING]
return "unknown"
def _tagstr(self, tag):
name = self.tags.getTagName(tag)
if name:
return name
return hex(tag)
def _load(self):
self.tag = self.br.read()
self.type = self.br.read()
self.count = self.br.read(4, "I")
self.offset = self.br.read(4, "I")
def read(self):
if not self.br:
return None
# To save time and space the Value Offset contains the Value instead of pointing to
# the Value if and only if the Value fits into 4 bytes. If the Value is shorter than 4
# bytes, it is left-justified within the 4-byte Value Offset, i.e., stored in the lowernumbered
# bytes. Whether the Value fits within 4 bytes is determined by the Type
# and Count of the field.
if not self.type in self.types.keys():
return None
if self.types[self.type][self.LENGTH] * self.count <= 4:
return self.offset
self.br.seek(self.offset)
if self.type in (TiffDirectoryEntry.BYTE, TiffDirectoryEntry.ASCII):
return self.br.read(self.types[self.type][self.LENGTH], self.types[self.type][self.FORMAT], self.count)
if self.type in (TiffDirectoryEntry.SHORT, TiffDirectoryEntry.LONG):
return self.br.read(
self.types[self.type][self.LENGTH], self.types[self.type][self.FORMAT], self.count, True
)
elif self.type == TiffDirectoryEntry.RATIONAL:
values = ()
for i in range(0, self.count):
numerator, denominator = self.br.read(self.types[self.type][self.LENGTH], "LL", 1, True)
values += ((numerator, denominator),)
return values
