Appendices

Exif Data in Piexif

Each exif tag has an appropriate data type (BYTE, ASCII, SHORT, etc.). Please see the official Exif standards for full documentation: http://www.cipa.jp/std/documents/e/DC-008-2012_E.pdf

Exif Type	Python Type(3.x)
BYTE	int
SIGNED BYTE	int
ASCII	str
SHORT	int
SIGNED SHORT	int
LONG	int
RATIONAL	(int, int)
UNDEFINED	bytes
SRATIONAL	(int, int)
FLOAT	float
DOUBLE	float

Values that are numerical (BYTE, SHORT, LONG, RATIONAL, or SRATIONAL) and that require two or more values should be expressed with a tuple.

BYTE, SHORT, LONG	(int, int, …)
RATIONAL, SRATIONAL	((int, int), (int, int), …)

Note

If the value type is numerical but only one value is required, a tuple of length 1 (e.g. (int,)) is also acceptable.

Exif in piexif example is below.

zeroth_ifd = {piexif.ImageIFD.Make: "Canon",  # ASCII, count any
              piexif.ImageIFD.XResolution: (96, 1),  # RATIONAL, count 1
              piexif.ImageIFD.YResolution: (96, 1),  # RATIONAL, count 1
              piexif.ImageIFD.Software: "piexif"  # ASCII, count any
              }
exif_ifd = {piexif.ExifIFD.ExifVersion: b"\x02\x00\x00\x00"  # UNDEFINED, count 4
            piexif.ExifIFD.LensMake: "LensMake",  # ASCII, count any
            piexif.ExifIFD.Sharpness: 65535,  # SHORT, count 1 ... also be accepted '(65535,)'
            piexif.ExifIFD.LensSpecification: ((1, 1), (1, 1), (1, 1), (1, 1)),  # Rational, count 4
            }
gps_ifd = {piexif.GPSIFD.GPSVersionID: (2, 0, 0, 0),  # BYTE, count 4
           piexif.GPSIFD.GPSAltitudeRef: 1,  # BYTE, count 1 ... also be accepted '(1,)'
           }
exif_dict = {"0th":zeroth_ifd, "Exif":exif_ifd, "GPS":gps_ifd}
exif_bytes = piexif.dump(exif_dict)

# round trip
piexif.insert(exif_bytes, "foo.jpg")
exif_dict_tripped = piexif.load("foo.jpg")

On GoogleAppEngine

Files cannot be saved to disk when using GoogleAppEngine. Therefore, files must be handled in memory.

jpg_data = self.request.get("jpeg")
output = io.BytesIO()

# load
exif = piexif.load(jpg_data)

# insert
piexif.insert(exif_bytes, jpg_data, output)

# remove
piexif.remove(jpg_data, output)

# transplant
piexif.transplant(jpg_data1, jpg_data2, output)

Invalid EXIF Thumbnails

EXIF data will sometimes be either corrupted or written by non-compliant software. When this happens, it’s possible that the thumbnail stored in EXIF cannot be found when attempting to dump the EXIF dictionary.

A good solution would be to remove the thumbnail from the EXIF dictionary and then re-attempt the dump:

try:
    exif_bytes = piexif.dump(exif_dict)
except InvalidImageDataError:
    del exif_dict["1st"]
    del exif_dict["thumbnail"]
    exif_bytes = piexif.dump(exif_dict)