EXIF.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Library to extract EXIF information from digital camera image files
# http://sourceforge.net/projects/exif-py/
#
# VERSION 1.1.0
#
# To use this library call with:
#    f = open(path_name, 'rb')
#    tags = EXIF.process_file(f)
#
# To ignore MakerNote tags, pass the -q or --quick
# command line arguments, or as
#    tags = EXIF.process_file(f, details=False)
#
# To stop processing after a certain tag is retrieved,
# pass the -t TAG or --stop-tag TAG argument, or as
#    tags = EXIF.process_file(f, stop_tag='TAG')
#
# where TAG is a valid tag name, ex 'DateTimeOriginal'
#
# These 2 are useful when you are retrieving a large list of images
#
#
# To return an error on invalid tags,
# pass the -s or --strict argument, or as
#    tags = EXIF.process_file(f, strict=True)
#
# Otherwise these tags will be ignored
#
# Returned tags will be a dictionary mapping names of EXIF tags to their
# values in the file named by path_name.  You can process the tags
# as you wish.  In particular, you can iterate through all the tags with:
#     for tag in tags.keys():
#         if tag not in ('JPEGThumbnail', 'TIFFThumbnail', 'Filename',
#                        'EXIF MakerNote'):
#             print "Key: %s, value %s" % (tag, tags[tag])
# (This code uses the if statement to avoid printing out a few of the
# tags that tend to be long or boring.)
#
# The tags dictionary will include keys for all of the usual EXIF
# tags, and will also include keys for Makernotes used by some
# cameras, for which we have a good specification.
#
# Note that the dictionary keys are the IFD name followed by the
# tag name. For example:
# 'EXIF DateTimeOriginal', 'Image Orientation', 'MakerNote FocusMode'
#
# Copyright (c) 2002-2007 Gene Cash All rights reserved
# Copyright (c) 2007-2008 Ianaré Sévi All rights reserved
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
#  1. Redistributions of source code must retain the above copyright
#     notice, this list of conditions and the following disclaimer.
#
#  2. Redistributions in binary form must reproduce the above
#     copyright notice, this list of conditions and the following
#     disclaimer in the documentation and/or other materials provided
#     with the distribution.
#
#  3. Neither the name of the authors nor the names of its contributors
#     may be used to endorse or promote products derived from this
#     software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
#
# ----- See 'changes.txt' file for all contributors and changes ----- #
#


# Don't throw an exception when given an out of range character.
def make_string(seq):
    str = ''
    for c in seq:
        # Screen out non-printing characters
        if 32 <= c and c < 256:
            str += chr(c)
    # If no printing chars
    if not str:
        return seq
    return str

# Special version to deal with the code in the first 8 bytes of a user comment.
# First 8 bytes gives coding system e.g. ASCII vs. JIS vs Unicode
def make_string_uc(seq):
    code = seq[0:8]
    seq = seq[8:]
    # Of course, this is only correct if ASCII, and the standard explicitly
    # allows JIS and Unicode.
    return make_string(seq)

# field type descriptions as (length, abbreviation, full name) tuples
FIELD_TYPES = (
    (0, 'X', 'Proprietary'), # no such type
    (1, 'B', 'Byte'),
    (1, 'A', 'ASCII'),
    (2, 'S', 'Short'),
    (4, 'L', 'Long'),
    (8, 'R', 'Ratio'),
    (1, 'SB', 'Signed Byte'),
    (1, 'U', 'Undefined'),
    (2, 'SS', 'Signed Short'),
    (4, 'SL', 'Signed Long'),
    (8, 'SR', 'Signed Ratio'),
    )

# dictionary of main EXIF tag names
# first element of tuple is tag name, optional second element is
# another dictionary giving names to values
EXIF_TAGS = {
    0x0100: ('ImageWidth', ),
    0x0101: ('ImageLength', ),
    0x0102: ('BitsPerSample', ),
    0x0103: ('Compression',
             {1: 'Uncompressed',
              2: 'CCITT 1D',
              3: 'T4/Group 3 Fax',
              4: 'T6/Group 4 Fax',
              5: 'LZW',
              6: 'JPEG (old-style)',
              7: 'JPEG',
              8: 'Adobe Deflate',
              9: 'JBIG B&W',
              10: 'JBIG Color',
              32766: 'Next',
              32769: 'Epson ERF Compressed',
              32771: 'CCIRLEW',
              32773: 'PackBits',
              32809: 'Thunderscan',
              32895: 'IT8CTPAD',
              32896: 'IT8LW',
              32897: 'IT8MP',
              32898: 'IT8BL',
              32908: 'PixarFilm',
              32909: 'PixarLog',
              32946: 'Deflate',
              32947: 'DCS',
              34661: 'JBIG',
              34676: 'SGILog',
              34677: 'SGILog24',
              34712: 'JPEG 2000',
              34713: 'Nikon NEF Compressed',
              65000: 'Kodak DCR Compressed',
              65535: 'Pentax PEF Compressed'}),
    0x0106: ('PhotometricInterpretation', ),
    0x0107: ('Thresholding', ),
    0x010A: ('FillOrder', ),
    0x010D: ('DocumentName', ),
    0x010E: ('ImageDescription', ),
    0x010F: ('Make', ),
    0x0110: ('Model', ),
    0x0111: ('StripOffsets', ),
    0x0112: ('Orientation',
             {1: 'Horizontal (normal)',
              2: 'Mirrored horizontal',
              3: 'Rotated 180',
              4: 'Mirrored vertical',
              5: 'Mirrored horizontal then rotated 90 CCW',
              6: 'Rotated 90 CW',
              7: 'Mirrored horizontal then rotated 90 CW',
              8: 'Rotated 90 CCW'}),
    0x0115: ('SamplesPerPixel', ),
    0x0116: ('RowsPerStrip', ),
    0x0117: ('StripByteCounts', ),
    0x011A: ('XResolution', ),
    0x011B: ('YResolution', ),
    0x011C: ('PlanarConfiguration', ),
    0x011D: ('PageName', make_string),
    0x0128: ('ResolutionUnit',
             {1: 'Not Absolute',
              2: 'Pixels/Inch',
              3: 'Pixels/Centimeter'}),
    0x012D: ('TransferFunction', ),
    0x0131: ('Software', ),
    0x0132: ('DateTime', ),
    0x013B: ('Artist', ),
    0x013E: ('WhitePoint', ),
    0x013F: ('PrimaryChromaticities', ),
    0x0156: ('TransferRange', ),
    0x0200: ('JPEGProc', ),
    0x0201: ('JPEGInterchangeFormat', ),
    0x0202: ('JPEGInterchangeFormatLength', ),
    0x0211: ('YCbCrCoefficients', ),
    0x0212: ('YCbCrSubSampling', ),
    0x0213: ('YCbCrPositioning',
             {1: 'Centered',
              2: 'Co-sited'}),
    0x0214: ('ReferenceBlackWhite', ),
    
    0x4746: ('Rating', ),
    
    0x828D: ('CFARepeatPatternDim', ),
    0x828E: ('CFAPattern', ),
    0x828F: ('BatteryLevel', ),
    0x8298: ('Copyright', ),
    0x829A: ('ExposureTime', ),
    0x829D: ('FNumber', ),
    0x83BB: ('IPTC/NAA', ),
    0x8769: ('ExifOffset', ),
    0x8773: ('InterColorProfile', ),
    0x8822: ('ExposureProgram',
             {0: 'Unidentified',
              1: 'Manual',
              2: 'Program Normal',
              3: 'Aperture Priority',
              4: 'Shutter Priority',
              5: 'Program Creative',
              6: 'Program Action',
              7: 'Portrait Mode',
              8: 'Landscape Mode'}),
    0x8824: ('SpectralSensitivity', ),
    0x8825: ('GPSInfo', ),
    0x8827: ('ISOSpeedRatings', ),
    0x8828: ('OECF', ),
    0x9000: ('ExifVersion', make_string),
    0x9003: ('DateTimeOriginal', ),
    0x9004: ('DateTimeDigitized', ),
    0x9101: ('ComponentsConfiguration',
             {0: '',
              1: 'Y',
              2: 'Cb',
              3: 'Cr',
              4: 'Red',
              5: 'Green',
              6: 'Blue'}),
    0x9102: ('CompressedBitsPerPixel', ),
    0x9201: ('ShutterSpeedValue', ),
    0x9202: ('ApertureValue', ),
    0x9203: ('BrightnessValue', ),
    0x9204: ('ExposureBiasValue', ),
    0x9205: ('MaxApertureValue', ),
    0x9206: ('SubjectDistance', ),
    0x9207: ('MeteringMode',
             {0: 'Unidentified',
              1: 'Average',
              2: 'CenterWeightedAverage',
              3: 'Spot',
              4: 'MultiSpot',
              5: 'Pattern'}),
    0x9208: ('LightSource',
             {0: 'Unknown',
              1: 'Daylight',
              2: 'Fluorescent',
              3: 'Tungsten',
              9: 'Fine Weather',
              10: 'Flash',
              11: 'Shade',
              12: 'Daylight Fluorescent',
              13: 'Day White Fluorescent',
              14: 'Cool White Fluorescent',
              15: 'White Fluorescent',
              17: 'Standard Light A',
              18: 'Standard Light B',
              19: 'Standard Light C',
              20: 'D55',
              21: 'D65',
              22: 'D75',
              255: 'Other'}),
    0x9209: ('Flash',
             {0: 'No',
              1: 'Fired',
              5: 'Fired (?)', # no return sensed
              7: 'Fired (!)', # return sensed
              9: 'Fill Fired',
              13: 'Fill Fired (?)',
              15: 'Fill Fired (!)',
              16: 'Off',
              24: 'Auto Off',
              25: 'Auto Fired',
              29: 'Auto Fired (?)',
              31: 'Auto Fired (!)',
              32: 'Not Available'}),
    0x920A: ('FocalLength', ),
    0x9214: ('SubjectArea', ),
    0x927C: ('MakerNote', ),
    0x9286: ('UserComment', make_string_uc),
    0x9290: ('SubSecTime', ),
    0x9291: ('SubSecTimeOriginal', ),
    0x9292: ('SubSecTimeDigitized', ),
    
    # used by Windows Explorer
    0x9C9B: ('XPTitle', ),
    0x9C9C: ('XPComment', ),
    0x9C9D: ('XPAuthor', ), #(ignored by Windows Explorer if Artist exists)
    0x9C9E: ('XPKeywords', ),
    0x9C9F: ('XPSubject', ),

    0xA000: ('FlashPixVersion', make_string),
    0xA001: ('ColorSpace',
             {1: 'sRGB',
              2: 'Adobe RGB',
              65535: 'Uncalibrated'}),
    0xA002: ('ExifImageWidth', ),
    0xA003: ('ExifImageLength', ),
    0xA005: ('InteroperabilityOffset', ),
    0xA20B: ('FlashEnergy', ),               # 0x920B in TIFF/EP
    0xA20C: ('SpatialFrequencyResponse', ),  # 0x920C
    0xA20E: ('FocalPlaneXResolution', ),     # 0x920E
    0xA20F: ('FocalPlaneYResolution', ),     # 0x920F
    0xA210: ('FocalPlaneResolutionUnit', ),  # 0x9210
    0xA214: ('SubjectLocation', ),           # 0x9214
    0xA215: ('ExposureIndex', ),             # 0x9215
    0xA217: ('SensingMethod',                # 0x9217
             {1: 'Not defined',
              2: 'One-chip color area',
              3: 'Two-chip color area',
              4: 'Three-chip color area',
              5: 'Color sequential area',
              7: 'Trilinear',
              8: 'Color sequential linear'}),             
    0xA300: ('FileSource',
             {1: 'Film Scanner',
              2: 'Reflection Print Scanner',
              3: 'Digital Camera'}),
    0xA301: ('SceneType',
             {1: 'Directly Photographed'}),
    0xA302: ('CVAPattern', ),
    0xA401: ('CustomRendered',
             {0: 'Normal',
              1: 'Custom'}),
    0xA402: ('ExposureMode',
             {0: 'Auto Exposure',
              1: 'Manual Exposure',
              2: 'Auto Bracket'}),
    0xA403: ('WhiteBalance',
             {0: 'Auto',
              1: 'Manual'}),
    0xA404: ('DigitalZoomRatio', ),
    0xA405: ('FocalLengthIn35mmFilm', ),
    0xA406: ('SceneCaptureType',
             {0: 'Standard',
              1: 'Landscape',
              2: 'Portrait',
              3: 'Night)'}),
    0xA407: ('GainControl',
             {0: 'None',
              1: 'Low gain up',
              2: 'High gain up',
              3: 'Low gain down',
              4: 'High gain down'}),
    0xA408: ('Contrast',
             {0: 'Normal',
              1: 'Soft',
              2: 'Hard'}),
    0xA409: ('Saturation',
             {0: 'Normal',
              1: 'Soft',
              2: 'Hard'}),
    0xA40A: ('Sharpness',
             {0: 'Normal',
              1: 'Soft',
              2: 'Hard'}),
    0xA40B: ('DeviceSettingDescription', ),
    0xA40C: ('SubjectDistanceRange', ),
    0xA500: ('Gamma', ),
    0xC4A5: ('PrintIM', ),
    0xEA1C:	('Padding', ),
    }

# interoperability tags
INTR_TAGS = {
    0x0001: ('InteroperabilityIndex', ),
    0x0002: ('InteroperabilityVersion', ),
    0x1000: ('RelatedImageFileFormat', ),
    0x1001: ('RelatedImageWidth', ),
    0x1002: ('RelatedImageLength', ),
    }

# GPS tags (not used yet, haven't seen camera with GPS)
GPS_TAGS = {
    0x0000: ('GPSVersionID', ),
    0x0001: ('GPSLatitudeRef', ),
    0x0002: ('GPSLatitude', ),
    0x0003: ('GPSLongitudeRef', ),
    0x0004: ('GPSLongitude', ),
    0x0005: ('GPSAltitudeRef', ),
    0x0006: ('GPSAltitude', ),
    0x0007: ('GPSTimeStamp', ),
    0x0008: ('GPSSatellites', ),
    0x0009: ('GPSStatus', ),
    0x000A: ('GPSMeasureMode', ),
    0x000B: ('GPSDOP', ),
    0x000C: ('GPSSpeedRef', ),
    0x000D: ('GPSSpeed', ),
    0x000E: ('GPSTrackRef', ),
    0x000F: ('GPSTrack', ),
    0x0010: ('GPSImgDirectionRef', ),
    0x0011: ('GPSImgDirection', ),
    0x0012: ('GPSMapDatum', ),
    0x0013: ('GPSDestLatitudeRef', ),
    0x0014: ('GPSDestLatitude', ),
    0x0015: ('GPSDestLongitudeRef', ),
    0x0016: ('GPSDestLongitude', ),
    0x0017: ('GPSDestBearingRef', ),
    0x0018: ('GPSDestBearing', ),
    0x0019: ('GPSDestDistanceRef', ),
    0x001A: ('GPSDestDistance', ),
    0x001D: ('GPSDate', ),
    }

# Ignore these tags when quick processing
# 0x927C is MakerNote Tags
# 0x9286 is user comment
IGNORE_TAGS=(0x9286, 0x927C)

# http://tomtia.plala.jp/DigitalCamera/MakerNote/index.asp
def nikon_ev_bias(seq):
    # First digit seems to be in steps of 1/6 EV.
    # Does the third value mean the step size?  It is usually 6,
    # but it is 12 for the ExposureDifference.
    #
    # Check for an error condition that could cause a crash.
    # This only happens if something has gone really wrong in
    # reading the Nikon MakerNote.
    if len( seq ) < 4 : return ""
    #
    if seq == [252, 1, 6, 0]:
        return "-2/3 EV"
    if seq == [253, 1, 6, 0]:
        return "-1/2 EV"
    if seq == [254, 1, 6, 0]:
        return "-1/3 EV"
    if seq == [0, 1, 6, 0]:
        return "0 EV"
    if seq == [2, 1, 6, 0]:
        return "+1/3 EV"
    if seq == [3, 1, 6, 0]:
        return "+1/2 EV"
    if seq == [4, 1, 6, 0]:
        return "+2/3 EV"
    # Handle combinations not in the table.
    a = seq[0]
    # Causes headaches for the +/- logic, so special case it.
    if a == 0:
        return "0 EV"
    if a > 127:
        a = 256 - a
        ret_str = "-"
    else:
        ret_str = "+"
    b = seq[2]	# Assume third value means the step size
    whole = a / b
    a = a % b
    if whole != 0:
        ret_str = ret_str + str(whole) + " "
    if a == 0:
        ret_str = ret_str + "EV"
    else:
        r = Ratio(a, b)
        ret_str = ret_str + r.__repr__() + " EV"
    return ret_str

# Nikon E99x MakerNote Tags
MAKERNOTE_NIKON_NEWER_TAGS={
    0x0001: ('MakernoteVersion', make_string),	# Sometimes binary
    0x0002: ('ISOSetting', make_string),
    0x0003: ('ColorMode', ),
    0x0004: ('Quality', ),
    0x0005: ('Whitebalance', ),
    0x0006: ('ImageSharpening', ),
    0x0007: ('FocusMode', ),
    0x0008: ('FlashSetting', ),
    0x0009: ('AutoFlashMode', ),
    0x000B: ('WhiteBalanceBias', ),
    0x000C: ('WhiteBalanceRBCoeff', ),
    0x000D: ('ProgramShift', nikon_ev_bias),
    # Nearly the same as the other EV vals, but step size is 1/12 EV (?)
    0x000E: ('ExposureDifference', nikon_ev_bias),
    0x000F: ('ISOSelection', ),
    0x0011: ('NikonPreview', ),
    0x0012: ('FlashCompensation', nikon_ev_bias),
    0x0013: ('ISOSpeedRequested', ),
    0x0016: ('PhotoCornerCoordinates', ),
    # 0x0017: Unknown, but most likely an EV value
    0x0018: ('FlashBracketCompensationApplied', nikon_ev_bias),
    0x0019: ('AEBracketCompensationApplied', ),
    0x001A: ('ImageProcessing', ),
    0x001B: ('CropHiSpeed', ),
    0x001D: ('SerialNumber', ),	# Conflict with 0x00A0 ?
    0x001E: ('ColorSpace', ),
    0x001F: ('VRInfo', ),
    0x0020: ('ImageAuthentication', ),
    0x0022: ('ActiveDLighting', ),
    0x0023: ('PictureControl', ),
    0x0024: ('WorldTime', ),
    0x0025: ('ISOInfo', ),
    0x0080: ('ImageAdjustment', ),
    0x0081: ('ToneCompensation', ),
    0x0082: ('AuxiliaryLens', ),
    0x0083: ('LensType', ),
    0x0084: ('LensMinMaxFocalMaxAperture', ),
    0x0085: ('ManualFocusDistance', ),
    0x0086: ('DigitalZoomFactor', ),
    0x0087: ('FlashMode',
             {0x00: 'Did Not Fire',
              0x01: 'Fired, Manual',
              0x07: 'Fired, External',
              0x08: 'Fired, Commander Mode ',
              0x09: 'Fired, TTL Mode'}),
    0x0088: ('AFFocusPosition',
             {0x0000: 'Center',
              0x0100: 'Top',
              0x0200: 'Bottom',
              0x0300: 'Left',
              0x0400: 'Right'}),
    0x0089: ('BracketingMode',
             {0x00: 'Single frame, no bracketing',
              0x01: 'Continuous, no bracketing',
              0x02: 'Timer, no bracketing',
              0x10: 'Single frame, exposure bracketing',
              0x11: 'Continuous, exposure bracketing',
              0x12: 'Timer, exposure bracketing',
              0x40: 'Single frame, white balance bracketing',
              0x41: 'Continuous, white balance bracketing',
              0x42: 'Timer, white balance bracketing'}),
    0x008A: ('AutoBracketRelease', ),
    0x008B: ('LensFStops', ),
    0x008C: ('NEFCurve1', ),	# ExifTool calls this 'ContrastCurve'
    0x008D: ('ColorMode', ),
    0x008F: ('SceneMode', ),
    0x0090: ('LightingType', ),
    0x0091: ('ShotInfo', ),	# First 4 bytes are a version number in ASCII
    0x0092: ('HueAdjustment', ),
    # ExifTool calls this 'NEFCompression', should be 1-4
    0x0093: ('Compression', ),
    0x0094: ('Saturation',
             {-3: 'B&W',
              -2: '-2',
              -1: '-1',
              0: '0',
              1: '1',
              2: '2'}),
    0x0095: ('NoiseReduction', ),
    0x0096: ('NEFCurve2', ),	# ExifTool calls this 'LinearizationTable'
    0x0097: ('ColorBalance', ),	# First 4 bytes are a version number in ASCII
    0x0098: ('LensData', ),	# First 4 bytes are a version number in ASCII
    0x0099: ('RawImageCenter', ),
    0x009A: ('SensorPixelSize', ),
    0x009C: ('Scene Assist', ),
    0x009E: ('RetouchHistory', ),
    0x00A0: ('SerialNumber', ),
    0x00A2: ('ImageDataSize', ),
    # 00A3: unknown - a single byte 0
    # 00A4: In NEF, looks like a 4 byte ASCII version number ('0200')
    0x00A5: ('ImageCount', ),
    0x00A6: ('DeletedImageCount', ),
    0x00A7: ('TotalShutterReleases', ),
    # First 4 bytes are a version number in ASCII, with version specific
    # info to follow.  Its hard to treat it as a string due to embedded nulls.
    0x00A8: ('FlashInfo', ),
    0x00A9: ('ImageOptimization', ),
    0x00AA: ('Saturation', ),
    0x00AB: ('DigitalVariProgram', ),
    0x00AC: ('ImageStabilization', ),
    0x00AD: ('Responsive AF', ),	# 'AFResponse'
    0x00B0: ('MultiExposure', ),
    0x00B1: ('HighISONoiseReduction', ),
    0x00B7: ('AFInfo', ),
    0x00B8: ('FileInfo', ),
    # 00B9: unknown
    0x0100: ('DigitalICE', ),
    0x0103: ('PreviewCompression',
             {1: 'Uncompressed',
              2: 'CCITT 1D',
              3: 'T4/Group 3 Fax',
              4: 'T6/Group 4 Fax',
              5: 'LZW',
              6: 'JPEG (old-style)',
              7: 'JPEG',
              8: 'Adobe Deflate',
              9: 'JBIG B&W',
              10: 'JBIG Color',
              32766: 'Next',
              32769: 'Epson ERF Compressed',
              32771: 'CCIRLEW',
              32773: 'PackBits',
              32809: 'Thunderscan',
              32895: 'IT8CTPAD',
              32896: 'IT8LW',
              32897: 'IT8MP',
              32898: 'IT8BL',
              32908: 'PixarFilm',
              32909: 'PixarLog',
              32946: 'Deflate',
              32947: 'DCS',
              34661: 'JBIG',
              34676: 'SGILog',
              34677: 'SGILog24',
              34712: 'JPEG 2000',
              34713: 'Nikon NEF Compressed',
              65000: 'Kodak DCR Compressed',
              65535: 'Pentax PEF Compressed',}),
    0x0201: ('PreviewImageStart', ),
    0x0202: ('PreviewImageLength', ),
    0x0213: ('PreviewYCbCrPositioning',
             {1: 'Centered',
              2: 'Co-sited'}), 
    0x0010: ('DataDump', ),
    }

MAKERNOTE_NIKON_OLDER_TAGS = {
    0x0003: ('Quality',
             {1: 'VGA Basic',
              2: 'VGA Normal',
              3: 'VGA Fine',
              4: 'SXGA Basic',
              5: 'SXGA Normal',
              6: 'SXGA Fine'}),
    0x0004: ('ColorMode',
             {1: 'Color',
              2: 'Monochrome'}),
    0x0005: ('ImageAdjustment',
             {0: 'Normal',
              1: 'Bright+',
              2: 'Bright-',
              3: 'Contrast+',
              4: 'Contrast-'}),
    0x0006: ('CCDSpeed',
             {0: 'ISO 80',
              2: 'ISO 160',
              4: 'ISO 320',
              5: 'ISO 100'}),
    0x0007: ('WhiteBalance',
             {0: 'Auto',
              1: 'Preset',
              2: 'Daylight',
              3: 'Incandescent',
              4: 'Fluorescent',
              5: 'Cloudy',
              6: 'Speed Light'}),
    }

# decode Olympus SpecialMode tag in MakerNote
def olympus_special_mode(v):
    a={
        0: 'Normal',
        1: 'Unknown',
        2: 'Fast',
        3: 'Panorama'}
    b={
        0: 'Non-panoramic',
        1: 'Left to right',
        2: 'Right to left',
        3: 'Bottom to top',
        4: 'Top to bottom'}
    if v[0] not in a or v[2] not in b:
        return v
    return '%s - sequence %d - %s' % (a[v[0]], v[1], b[v[2]])

MAKERNOTE_OLYMPUS_TAGS={
    # ah HAH! those sneeeeeaky bastids! this is how they get past the fact
    # that a JPEG thumbnail is not allowed in an uncompressed TIFF file
    0x0100: ('JPEGThumbnail', ),
    0x0200: ('SpecialMode', olympus_special_mode),
    0x0201: ('JPEGQual',
             {1: 'SQ',
              2: 'HQ',
              3: 'SHQ'}),
    0x0202: ('Macro',
             {0: 'Normal',
             1: 'Macro',
             2: 'SuperMacro'}),
    0x0203: ('BWMode',
             {0: 'Off',
             1: 'On'}),
    0x0204: ('DigitalZoom', ),
    0x0205: ('FocalPlaneDiagonal', ),
    0x0206: ('LensDistortionParams', ),
    0x0207: ('SoftwareRelease', ),
    0x0208: ('PictureInfo', ),
    0x0209: ('CameraID', make_string), # print as string
    0x0F00: ('DataDump', ),
    0x0300: ('PreCaptureFrames', ),
    0x0404: ('SerialNumber', ),
    0x1000: ('ShutterSpeedValue', ),
    0x1001: ('ISOValue', ),
    0x1002: ('ApertureValue', ),
    0x1003: ('BrightnessValue', ),
    0x1004: ('FlashMode', ),
    0x1004: ('FlashMode',
       {2: 'On',
        3: 'Off'}),
    0x1005: ('FlashDevice',
       {0: 'None',
        1: 'Internal',
        4: 'External',
        5: 'Internal + External'}),
    0x1006: ('ExposureCompensation', ),
    0x1007: ('SensorTemperature', ),
    0x1008: ('LensTemperature', ),
    0x100b: ('FocusMode',
       {0: 'Auto',
        1: 'Manual'}),
    0x1017: ('RedBalance', ),
    0x1018: ('BlueBalance', ),
    0x101a: ('SerialNumber', ),
    0x1023: ('FlashExposureComp', ),
    0x1026: ('ExternalFlashBounce',
       {0: 'No',
        1: 'Yes'}),
    0x1027: ('ExternalFlashZoom', ),
    0x1028: ('ExternalFlashMode', ),
    0x1029: ('Contrast 	int16u',
       {0: 'High',
        1: 'Normal',
        2: 'Low'}),
    0x102a: ('SharpnessFactor', ),
    0x102b: ('ColorControl', ),
    0x102c: ('ValidBits', ),
    0x102d: ('CoringFilter', ),
    0x102e: ('OlympusImageWidth', ),
    0x102f: ('OlympusImageHeight', ),
    0x1034: ('CompressionRatio', ),
    0x1035: ('PreviewImageValid',
       {0: 'No',
        1: 'Yes'}),
    0x1036: ('PreviewImageStart', ),
    0x1037: ('PreviewImageLength', ),
    0x1039: ('CCDScanMode',
       {0: 'Interlaced',
        1: 'Progressive'}),
    0x103a: ('NoiseReduction',
       {0: 'Off',
        1: 'On'}),
    0x103b: ('InfinityLensStep', ),
    0x103c: ('NearLensStep', ),

    # TODO - these need extra definitions
    # http://search.cpan.org/src/EXIFTOOL/Image-ExifTool-6.90/html/TagNames/Olympus.html
    0x2010: ('Equipment', ),
    0x2020: ('CameraSettings', ),
    0x2030: ('RawDevelopment', ),
    0x2040: ('ImageProcessing', ),
    0x2050: ('FocusInfo', ),
    0x3000: ('RawInfo ', ),
    }

# 0x2020 CameraSettings
MAKERNOTE_OLYMPUS_TAG_0x2020={
    0x0100: ('PreviewImageValid',
             {0: 'No',
              1: 'Yes'}),
    0x0101: ('PreviewImageStart', ),
    0x0102: ('PreviewImageLength', ),
    0x0200: ('ExposureMode',
             {1: 'Manual',
              2: 'Program',
              3: 'Aperture-priority AE',
              4: 'Shutter speed priority AE',
              5: 'Program-shift'}),
    0x0201: ('AELock',
             {0: 'Off',
              1: 'On'}),
    0x0202: ('MeteringMode',
             {2: 'Center Weighted',
              3: 'Spot',
              5: 'ESP',
              261: 'Pattern+AF',
              515: 'Spot+Highlight control',
              1027: 'Spot+Shadow control'}),
    0x0300: ('MacroMode',
             {0: 'Off',
              1: 'On'}),
    0x0301: ('FocusMode',
             {0: 'Single AF',
              1: 'Sequential shooting AF',
              2: 'Continuous AF',
              3: 'Multi AF',
              10: 'MF'}),
    0x0302: ('FocusProcess',
             {0: 'AF Not Used',
              1: 'AF Used'}),
    0x0303: ('AFSearch',
             {0: 'Not Ready',
              1: 'Ready'}),
    0x0304: ('AFAreas', ),
    0x0401: ('FlashExposureCompensation', ),
    0x0500: ('WhiteBalance2',
             {0: 'Auto',
             16: '7500K (Fine Weather with Shade)',
             17: '6000K (Cloudy)',
             18: '5300K (Fine Weather)',
             20: '3000K (Tungsten light)',
             21: '3600K (Tungsten light-like)',
             33: '6600K (Daylight fluorescent)',
             34: '4500K (Neutral white fluorescent)',
             35: '4000K (Cool white fluorescent)',
             48: '3600K (Tungsten light-like)',
             256: 'Custom WB 1',
             257: 'Custom WB 2',
             258: 'Custom WB 3',
             259: 'Custom WB 4',
             512: 'Custom WB 5400K',
             513: 'Custom WB 2900K',
             514: 'Custom WB 8000K', }),
    0x0501: ('WhiteBalanceTemperature', ),
    0x0502: ('WhiteBalanceBracket', ),
    0x0503: ('CustomSaturation', ), # (3 numbers: 1. CS Value, 2. Min, 3. Max)
    0x0504: ('ModifiedSaturation',
             {0: 'Off',
              1: 'CM1 (Red Enhance)',
              2: 'CM2 (Green Enhance)',
              3: 'CM3 (Blue Enhance)',
              4: 'CM4 (Skin Tones)'}),
    0x0505: ('ContrastSetting', ), # (3 numbers: 1. Contrast, 2. Min, 3. Max)
    0x0506: ('SharpnessSetting', ), # (3 numbers: 1. Sharpness, 2. Min, 3. Max)
    0x0507: ('ColorSpace',
             {0: 'sRGB',
              1: 'Adobe RGB',
              2: 'Pro Photo RGB'}),
    0x0509: ('SceneMode',
             {0: 'Standard',
              6: 'Auto',
              7: 'Sport',
              8: 'Portrait',
              9: 'Landscape+Portrait',
             10: 'Landscape',
             11: 'Night scene',
             13: 'Panorama',
             16: 'Landscape+Portrait',
             17: 'Night+Portrait',
             19: 'Fireworks',
             20: 'Sunset',
             22: 'Macro',
             25: 'Documents',
             26: 'Museum',
             28: 'Beach&Snow',
             30: 'Candle',
             35: 'Underwater Wide1',
             36: 'Underwater Macro',
             39: 'High Key',
             40: 'Digital Image Stabilization',
             44: 'Underwater Wide2',
             45: 'Low Key',
             46: 'Children',
             48: 'Nature Macro'}),
    0x050a: ('NoiseReduction',
             {0: 'Off',
              1: 'Noise Reduction',
              2: 'Noise Filter',
              3: 'Noise Reduction + Noise Filter',
              4: 'Noise Filter (ISO Boost)',
              5: 'Noise Reduction + Noise Filter (ISO Boost)'}),
    0x050b: ('DistortionCorrection',
             {0: 'Off',
              1: 'On'}),
    0x050c: ('ShadingCompensation',
             {0: 'Off',
              1: 'On'}),
    0x050d: ('CompressionFactor', ),
    0x050f: ('Gradation',
             {'-1 -1 1': 'Low Key',
              '0 -1 1': 'Normal',
              '1 -1 1': 'High Key'}),
    0x0520: ('PictureMode',
             {1: 'Vivid',
              2: 'Natural',
              3: 'Muted',
              256: 'Monotone',
              512: 'Sepia'}),
    0x0521: ('PictureModeSaturation', ),
    0x0522: ('PictureModeHue?', ),
    0x0523: ('PictureModeContrast', ),
    0x0524: ('PictureModeSharpness', ),
    0x0525: ('PictureModeBWFilter',
             {0: 'n/a',
              1: 'Neutral',
              2: 'Yellow',
              3: 'Orange',
              4: 'Red',
              5: 'Green'}),
    0x0526: ('PictureModeTone',
             {0: 'n/a',
              1: 'Neutral',
              2: 'Sepia',
              3: 'Blue',
              4: 'Purple',
              5: 'Green'}),
    0x0600: ('Sequence', ), # 2 or 3 numbers: 1. Mode, 2. Shot number, 3. Mode bits
    0x0601: ('PanoramaMode', ), # (2 numbers: 1. Mode, 2. Shot number)
    0x0603: ('ImageQuality2',
             {1: 'SQ',
              2: 'HQ',
              3: 'SHQ',
              4: 'RAW'}),
    0x0901: ('ManometerReading', ),
    }


MAKERNOTE_CASIO_TAGS={
    0x0001: ('RecordingMode',
             {1: 'Single Shutter',
              2: 'Panorama',
              3: 'Night Scene',
              4: 'Portrait',
              5: 'Landscape'}),
    0x0002: ('Quality',
             {1: 'Economy',
              2: 'Normal',
              3: 'Fine'}),
    0x0003: ('FocusingMode',
             {2: 'Macro',
              3: 'Auto Focus',
              4: 'Manual Focus',
              5: 'Infinity'}),
    0x0004: ('FlashMode',
             {1: 'Auto',
              2: 'On',
              3: 'Off',
              4: 'Red Eye Reduction'}),
    0x0005: ('FlashIntensity',
             {11: 'Weak',
              13: 'Normal',
              15: 'Strong'}),
    0x0006: ('Object Distance', ),
    0x0007: ('WhiteBalance',
             {1: 'Auto',
              2: 'Tungsten',
              3: 'Daylight',
              4: 'Fluorescent',
              5: 'Shade',
              129: 'Manual'}),
    0x000B: ('Sharpness',
             {0: 'Normal',
              1: 'Soft',
              2: 'Hard'}),
    0x000C: ('Contrast',
             {0: 'Normal',
              1: 'Low',
              2: 'High'}),
    0x000D: ('Saturation',
             {0: 'Normal',
              1: 'Low',
              2: 'High'}),
    0x0014: ('CCDSpeed',
             {64: 'Normal',
              80: 'Normal',
              100: 'High',
              125: '+1.0',
              244: '+3.0',
              250: '+2.0'}),
    }

MAKERNOTE_FUJIFILM_TAGS={
    0x0000: ('NoteVersion', make_string),
    0x1000: ('Quality', ),
    0x1001: ('Sharpness',
             {1: 'Soft',
              2: 'Soft',
              3: 'Normal',
              4: 'Hard',
              5: 'Hard'}),
    0x1002: ('WhiteBalance',
             {0: 'Auto',
              256: 'Daylight',
              512: 'Cloudy',
              768: 'DaylightColor-Fluorescent',
              769: 'DaywhiteColor-Fluorescent',
              770: 'White-Fluorescent',
              1024: 'Incandescent',
              3840: 'Custom'}),
    0x1003: ('Color',
             {0: 'Normal',
              256: 'High',
              512: 'Low'}),
    0x1004: ('Tone',
             {0: 'Normal',
              256: 'High',
              512: 'Low'}),
    0x1010: ('FlashMode',
             {0: 'Auto',
              1: 'On',
              2: 'Off',
              3: 'Red Eye Reduction'}),
    0x1011: ('FlashStrength', ),
    0x1020: ('Macro',
             {0: 'Off',
              1: 'On'}),
    0x1021: ('FocusMode',
             {0: 'Auto',
              1: 'Manual'}),
    0x1030: ('SlowSync',
             {0: 'Off',
              1: 'On'}),
    0x1031: ('PictureMode',
             {0: 'Auto',
              1: 'Portrait',
              2: 'Landscape',
              4: 'Sports',
              5: 'Night',
              6: 'Program AE',
              256: 'Aperture Priority AE',
              512: 'Shutter Priority AE',
              768: 'Manual Exposure'}),
    0x1100: ('MotorOrBracket',
             {0: 'Off',
              1: 'On'}),
    0x1300: ('BlurWarning',
             {0: 'Off',
              1: 'On'}),
    0x1301: ('FocusWarning',
             {0: 'Off',
              1: 'On'}),
    0x1302: ('AEWarning',
             {0: 'Off',
              1: 'On'}),
    }

MAKERNOTE_CANON_TAGS = {
    0x0006: ('ImageType', ),
    0x0007: ('FirmwareVersion', ),
    0x0008: ('ImageNumber', ),
    0x0009: ('OwnerName', ),
    }

# this is in element offset, name, optional value dictionary format
MAKERNOTE_CANON_TAG_0x001 = {
    1: ('Macromode',
        {1: 'Macro',
         2: 'Normal'}),
    2: ('SelfTimer', ),
    3: ('Quality',
        {2: 'Normal',
         3: 'Fine',
         5: 'Superfine'}),
    4: ('FlashMode',
        {0: 'Flash Not Fired',
         1: 'Auto',
         2: 'On',
         3: 'Red-Eye Reduction',
         4: 'Slow Synchro',
         5: 'Auto + Red-Eye Reduction',
         6: 'On + Red-Eye Reduction',
         16: 'external flash'}),
    5: ('ContinuousDriveMode',
        {0: 'Single Or Timer',
         1: 'Continuous'}),
    7: ('FocusMode',
        {0: 'One-Shot',
         1: 'AI Servo',
         2: 'AI Focus',
         3: 'MF',
         4: 'Single',
         5: 'Continuous',
         6: 'MF'}),
    10: ('ImageSize',
         {0: 'Large',
          1: 'Medium',
          2: 'Small'}),
    11: ('EasyShootingMode',
         {0: 'Full Auto',
          1: 'Manual',
          2: 'Landscape',
          3: 'Fast Shutter',
          4: 'Slow Shutter',
          5: 'Night',
          6: 'B&W',
          7: 'Sepia',
          8: 'Portrait',
          9: 'Sports',
          10: 'Macro/Close-Up',
          11: 'Pan Focus'}),
    12: ('DigitalZoom',
         {0: 'None',
          1: '2x',
          2: '4x'}),
    13: ('Contrast',
         {0xFFFF: 'Low',
          0: 'Normal',
          1: 'High'}),
    14: ('Saturation',
         {0xFFFF: 'Low',
          0: 'Normal',
          1: 'High'}),
    15: ('Sharpness',
         {0xFFFF: 'Low',
          0: 'Normal',
          1: 'High'}),
    16: ('ISO',
         {0: 'See ISOSpeedRatings Tag',
          15: 'Auto',
          16: '50',
          17: '100',
          18: '200',
          19: '400'}),
    17: ('MeteringMode',
         {3: 'Evaluative',
          4: 'Partial',
          5: 'Center-weighted'}),
    18: ('FocusType',
         {0: 'Manual',
          1: 'Auto',
          3: 'Close-Up (Macro)',
          8: 'Locked (Pan Mode)'}),
    19: ('AFPointSelected',
         {0x3000: 'None (MF)',
          0x3001: 'Auto-Selected',
          0x3002: 'Right',
          0x3003: 'Center',
          0x3004: 'Left'}),
    20: ('ExposureMode',
         {0: 'Easy Shooting',
          1: 'Program',
          2: 'Tv-priority',
          3: 'Av-priority',
          4: 'Manual',
          5: 'A-DEP'}),
    23: ('LongFocalLengthOfLensInFocalUnits', ),
    24: ('ShortFocalLengthOfLensInFocalUnits', ),
    25: ('FocalUnitsPerMM', ),
    28: ('FlashActivity',
         {0: 'Did Not Fire',
          1: 'Fired'}),
    29: ('FlashDetails',
         {14: 'External E-TTL',
          13: 'Internal Flash',
          11: 'FP Sync Used',
          7: '2nd("Rear")-Curtain Sync Used',
          4: 'FP Sync Enabled'}),
    32: ('FocusMode',
         {0: 'Single',
          1: 'Continuous'}),
    }

MAKERNOTE_CANON_TAG_0x004 = {
    7: ('WhiteBalance',
        {0: 'Auto',
         1: 'Sunny',
         2: 'Cloudy',
         3: 'Tungsten',
         4: 'Fluorescent',
         5: 'Flash',
         6: 'Custom'}),
    9: ('SequenceNumber', ),
    14: ('AFPointUsed', ),
    15: ('FlashBias',
         {0xFFC0: '-2 EV',
          0xFFCC: '-1.67 EV',
          0xFFD0: '-1.50 EV',
          0xFFD4: '-1.33 EV',
          0xFFE0: '-1 EV',
          0xFFEC: '-0.67 EV',
          0xFFF0: '-0.50 EV',
          0xFFF4: '-0.33 EV',
          0x0000: '0 EV',
          0x000C: '0.33 EV',
          0x0010: '0.50 EV',
          0x0014: '0.67 EV',
          0x0020: '1 EV',
          0x002C: '1.33 EV',
          0x0030: '1.50 EV',
          0x0034: '1.67 EV',
          0x0040: '2 EV'}),
    19: ('SubjectDistance', ),
    }

# extract multibyte integer in Motorola format (little endian)
def s2n_motorola(str):
    x = 0
    for c in str:
        x = (x << 8) | ord(c)
    return x

# extract multibyte integer in Intel format (big endian)
def s2n_intel(str):
    x = 0
    y = 0L
    for c in str:
        x = x | (ord(c) << y)
        y = y + 8
    return x

# ratio object that eventually will be able to reduce itself to lowest
# common denominator for printing
def gcd(a, b):
    if b == 0:
        return a
    else:
        return gcd(b, a % b)

class Ratio:
    def __init__(self, num, den):
        self.num = num
        self.den = den

    def __repr__(self):
        self.reduce()
        if self.den == 1:
            return str(self.num)
        return '%d/%d' % (self.num, self.den)

    def reduce(self):
        div = gcd(self.num, self.den)
        if div > 1:
            self.num = self.num / div
            self.den = self.den / div

# for ease of dealing with tags
class IFD_Tag:
    def __init__(self, printable, tag, field_type, values, field_offset,
                 field_length):
        # printable version of data
        self.printable = printable
        # tag ID number
        self.tag = tag
        # field type as index into FIELD_TYPES
        self.field_type = field_type
        # offset of start of field in bytes from beginning of IFD
        self.field_offset = field_offset
        # length of data field in bytes
        self.field_length = field_length
        # either a string or array of data items
        self.values = values

    def __str__(self):
        return self.printable

    def __repr__(self):
        return '(0x%04X) %s=%s @ %d' % (self.tag,
                                        FIELD_TYPES[self.field_type][2],
                                        self.printable,
                                        self.field_offset)

# class that handles an EXIF header
class EXIF_header:
    def __init__(self, file, endian, offset, fake_exif, strict, debug=0):
        self.file = file
        self.endian = endian
        self.offset = offset
        self.fake_exif = fake_exif
        self.strict = strict
        self.debug = debug
        self.tags = {}

    # convert slice to integer, based on sign and endian flags
    # usually this offset is assumed to be relative to the beginning of the
    # start of the EXIF information.  For some cameras that use relative tags,
    # this offset may be relative to some other starting point.
    def s2n(self, offset, length, signed=0):
        self.file.seek(self.offset+offset)
        slice=self.file.read(length)
        if self.endian == 'I':
            val=s2n_intel(slice)
        else:
            val=s2n_motorola(slice)
        # Sign extension ?
        if signed:
            msb=1L << (8*length-1)
            if val & msb:
                val=val-(msb << 1)
        return val

    # convert offset to string
    def n2s(self, offset, length):
        s = ''
        for dummy in range(length):
            if self.endian == 'I':
                s = s + chr(offset & 0xFF)
            else:
                s = chr(offset & 0xFF) + s
            offset = offset >> 8
        return s

    # return first IFD
    def first_IFD(self):
        return self.s2n(4, 4)

    # return pointer to next IFD
    def next_IFD(self, ifd):
        entries=self.s2n(ifd, 2)
        return self.s2n(ifd+2+12*entries, 4)

    # return list of IFDs in header
    def list_IFDs(self):
        i=self.first_IFD()
        a=[]
        while i:
            a.append(i)
            i=self.next_IFD(i)
        return a

    # return list of entries in this IFD
    def dump_IFD(self, ifd, ifd_name, dict=EXIF_TAGS, relative=0, stop_tag='UNDEF'):
        entries=self.s2n(ifd, 2)
        for i in range(entries):
            # entry is index of start of this IFD in the file
            entry = ifd + 2 + 12 * i
            tag = self.s2n(entry, 2)

            # get tag name early to avoid errors, help debug
            tag_entry = dict.get(tag)
            if tag_entry:
                tag_name = tag_entry[0]
            else:
                tag_name = 'Tag 0x%04X' % tag

            # ignore certain tags for faster processing
            if not (not detailed and tag in IGNORE_TAGS):
                field_type = self.s2n(entry + 2, 2)
                
                # unknown field type
                if not 0 < field_type < len(FIELD_TYPES):
                    if not self.strict:
                        continue
                    else:
                        raise ValueError('unknown type %d in tag 0x%04X' % (field_type, tag))

                typelen = FIELD_TYPES[field_type][0]
                count = self.s2n(entry + 4, 4)
                # Adjust for tag id/type/count (2+2+4 bytes)
                # Now we point at either the data or the 2nd level offset
                offset = entry + 8

                # If the value fits in 4 bytes, it is inlined, else we
                # need to jump ahead again.
                if count * typelen > 4:
                    # offset is not the value; it's a pointer to the value
                    # if relative we set things up so s2n will seek to the right
                    # place when it adds self.offset.  Note that this 'relative'
                    # is for the Nikon type 3 makernote.  Other cameras may use
                    # other relative offsets, which would have to be computed here
                    # slightly differently.
                    if relative:
                        tmp_offset = self.s2n(offset, 4)
                        offset = tmp_offset + ifd - 8
                        if self.fake_exif:
                            offset = offset + 18
                    else:
                        offset = self.s2n(offset, 4)

                field_offset = offset
                if field_type == 2:
                    # special case: null-terminated ASCII string
                    # XXX investigate
                    # sometimes gets too big to fit in int value
                    if count != 0 and count < (2**31):
                        self.file.seek(self.offset + offset)
                        values = self.file.read(count)
                        #print values
                        # Drop any garbage after a null.
                        values = values.split('\x00', 1)[0]
                    else:
                        values = ''
                else:
                    values = []
                    signed = (field_type in [6, 8, 9, 10])
                    
                    # XXX investigate
                    # some entries get too big to handle could be malformed
                    # file or problem with self.s2n
                    if count < 1000:
                        for dummy in range(count):
                            if field_type in (5, 10):
                                # a ratio
                                value = Ratio(self.s2n(offset, 4, signed),
                                              self.s2n(offset + 4, 4, signed))
                            else:
                                value = self.s2n(offset, typelen, signed)
                            values.append(value)
                            offset = offset + typelen
                    # The test above causes problems with tags that are 
                    # supposed to have long values!  Fix up one important case.
                    elif tag_name == 'MakerNote' :
                        for dummy in range(count):
                            value = self.s2n(offset, typelen, signed)
                            values.append(value)
                            offset = offset + typelen
                    #else :
                    #    print "Warning: dropping large tag:", tag, tag_name
                
                # now 'values' is either a string or an array
                if count == 1 and field_type != 2:
                    printable=str(values[0])
                elif count > 50 and len(values) > 20 :
                    printable=str( values[0:20] )[0:-1] + ", ... ]"
                else:
                    printable=str(values)

                # compute printable version of values
                if tag_entry:
                    if len(tag_entry) != 1:
                        # optional 2nd tag element is present
                        if callable(tag_entry[1]):
                            # call mapping function
                            printable = tag_entry[1](values)
                        else:
                            printable = ''
                            for i in values:
                                # use lookup table for this tag
                                printable += tag_entry[1].get(i, repr(i))

                self.tags[ifd_name + ' ' + tag_name] = IFD_Tag(printable, tag,
                                                          field_type,
                                                          values, field_offset,
                                                          count * typelen)
                if self.debug:
                    print ' debug:   %s: %s' % (tag_name,
                                                repr(self.tags[ifd_name + ' ' + tag_name]))

            if tag_name == stop_tag:
                break

    # extract uncompressed TIFF thumbnail (like pulling teeth)
    # we take advantage of the pre-existing layout in the thumbnail IFD as
    # much as possible
    def extract_TIFF_thumbnail(self, thumb_ifd):
        entries = self.s2n(thumb_ifd, 2)
        # this is header plus offset to IFD ...
        if self.endian == 'M':
            tiff = 'MM\x00*\x00\x00\x00\x08'
        else:
            tiff = 'II*\x00\x08\x00\x00\x00'
        # ... plus thumbnail IFD data plus a null "next IFD" pointer
        self.file.seek(self.offset+thumb_ifd)
        tiff += self.file.read(entries*12+2)+'\x00\x00\x00\x00'

        # fix up large value offset pointers into data area
        for i in range(entries):
            entry = thumb_ifd + 2 + 12 * i
            tag = self.s2n(entry, 2)
            field_type = self.s2n(entry+2, 2)
            typelen = FIELD_TYPES[field_type][0]
            count = self.s2n(entry+4, 4)
            oldoff = self.s2n(entry+8, 4)
            # start of the 4-byte pointer area in entry
            ptr = i * 12 + 18
            # remember strip offsets location
            if tag == 0x0111:
                strip_off = ptr
                strip_len = count * typelen
            # is it in the data area?
            if count * typelen > 4:
                # update offset pointer (nasty "strings are immutable" crap)
                # should be able to say "tiff[ptr:ptr+4]=newoff"
                newoff = len(tiff)
                tiff = tiff[:ptr] + self.n2s(newoff, 4) + tiff[ptr+4:]
                # remember strip offsets location
                if tag == 0x0111:
                    strip_off = newoff
                    strip_len = 4
                # get original data and store it
                self.file.seek(self.offset + oldoff)
                tiff += self.file.read(count * typelen)

        # add pixel strips and update strip offset info
        old_offsets = self.tags['Thumbnail StripOffsets'].values
        old_counts = self.tags['Thumbnail StripByteCounts'].values
        for i in range(len(old_offsets)):
            # update offset pointer (more nasty "strings are immutable" crap)
            offset = self.n2s(len(tiff), strip_len)
            tiff = tiff[:strip_off] + offset + tiff[strip_off + strip_len:]
            strip_off += strip_len
            # add pixel strip to end
            self.file.seek(self.offset + old_offsets[i])
            tiff += self.file.read(old_counts[i])

        self.tags['TIFFThumbnail'] = tiff

    # decode all the camera-specific MakerNote formats

    # Note is the data that comprises this MakerNote.  The MakerNote will
    # likely have pointers in it that point to other parts of the file.  We'll
    # use self.offset as the starting point for most of those pointers, since
    # they are relative to the beginning of the file.
    #
    # If the MakerNote is in a newer format, it may use relative addressing
    # within the MakerNote.  In that case we'll use relative addresses for the
    # pointers.
    #
    # As an aside: it's not just to be annoying that the manufacturers use
    # relative offsets.  It's so that if the makernote has to be moved by the
    # picture software all of the offsets don't have to be adjusted.  Overall,
    # this is probably the right strategy for makernotes, though the spec is
    # ambiguous.  (The spec does not appear to imagine that makernotes would
    # follow EXIF format internally.  Once they did, it's ambiguous whether
    # the offsets should be from the header at the start of all the EXIF info,
    # or from the header at the start of the makernote.)
    def decode_maker_note(self):
        note = self.tags['EXIF MakerNote']
        
        # Some apps use MakerNote tags but do not use a format for which we
        # have a description, so just do a raw dump for these.
        #if self.tags.has_key('Image Make'):
        make = self.tags['Image Make'].printable
        #else:
        #    make = ''

        # model = self.tags['Image Model'].printable # unused

        # Nikon
        # The maker note usually starts with the word Nikon, followed by the
        # type of the makernote (1 or 2, as a short).  If the word Nikon is
        # not at the start of the makernote, it's probably type 2, since some
        # cameras work that way.
        if 'NIKON' in make:
            if note.values[0:7] == [78, 105, 107, 111, 110, 0, 1]:
                if self.debug:
                    print "Looks like a type 1 Nikon MakerNote."
                self.dump_IFD(note.field_offset+8, 'MakerNote',
                              dict=MAKERNOTE_NIKON_OLDER_TAGS)
            elif note.values[0:7] == [78, 105, 107, 111, 110, 0, 2]:
                if self.debug:
                    print "Looks like a labeled type 2 Nikon MakerNote"
                if note.values[12:14] != [0, 42] and note.values[12:14] != [42L, 0L]:
                    raise ValueError("Missing marker tag '42' in MakerNote.")
                # skip the Makernote label and the TIFF header
                self.dump_IFD(note.field_offset+10+8, 'MakerNote',
                              dict=MAKERNOTE_NIKON_NEWER_TAGS, relative=1)
            else:
                # E99x or D1
                if self.debug:
                    print "Looks like an unlabeled type 2 Nikon MakerNote"
                self.dump_IFD(note.field_offset, 'MakerNote',
                              dict=MAKERNOTE_NIKON_NEWER_TAGS)
            return

        # Olympus
        if make.startswith('OLYMPUS'):
            self.dump_IFD(note.field_offset+8, 'MakerNote',
                          dict=MAKERNOTE_OLYMPUS_TAGS)
            # XXX TODO
            #for i in (('MakerNote Tag 0x2020', MAKERNOTE_OLYMPUS_TAG_0x2020),):
            #    self.decode_olympus_tag(self.tags[i[0]].values, i[1])
            #return

        # Casio
        if 'CASIO' in make or 'Casio' in make:
            self.dump_IFD(note.field_offset, 'MakerNote',
                          dict=MAKERNOTE_CASIO_TAGS)
            return

        # Fujifilm
        if make == 'FUJIFILM':
            # bug: everything else is "Motorola" endian, but the MakerNote
            # is "Intel" endian
            endian = self.endian
            self.endian = 'I'
            # bug: IFD offsets are from beginning of MakerNote, not
            # beginning of file header
            offset = self.offset
            self.offset += note.field_offset
            # process note with bogus values (note is actually at offset 12)
            self.dump_IFD(12, 'MakerNote', dict=MAKERNOTE_FUJIFILM_TAGS)
            # reset to correct values
            self.endian = endian
            self.offset = offset
            return

        # Canon
        if make == 'Canon':
            self.dump_IFD(note.field_offset, 'MakerNote',
                          dict=MAKERNOTE_CANON_TAGS)
            for i in (('MakerNote Tag 0x0001', MAKERNOTE_CANON_TAG_0x001),
                      ('MakerNote Tag 0x0004', MAKERNOTE_CANON_TAG_0x004)):
                self.canon_decode_tag(self.tags[i[0]].values, i[1])
            return


    # XXX TODO decode Olympus MakerNote tag based on offset within tag
    def olympus_decode_tag(self, value, dict):
        pass

    # decode Canon MakerNote tag based on offset within tag
    # see http://www.burren.cx/david/canon.html by David Burren
    def canon_decode_tag(self, value, dict):
        for i in range(1, len(value)):
            x=dict.get(i, ('Unknown', ))
            if self.debug:
                print i, x
            name=x[0]
            if len(x) > 1:
                val=x[1].get(value[i], 'Unknown')
            else:
                val=value[i]
            # it's not a real IFD Tag but we fake one to make everybody
            # happy. this will have a "proprietary" type
            self.tags['MakerNote '+name]=IFD_Tag(str(val), None, 0, None,
                                                 None, None)

# process an image file (expects an open file object)
# this is the function that has to deal with all the arbitrary nasty bits
# of the EXIF standard
def process_file(f, stop_tag='UNDEF', details=True, strict=False, debug=False):
    # yah it's cheesy...
    global detailed
    detailed = details

    # by default do not fake an EXIF beginning
    fake_exif = 0

    # determine whether it's a JPEG or TIFF
    data = f.read(12)
    if data[0:4] in ['II*\x00', 'MM\x00*']:
        # it's a TIFF file
        f.seek(0)
        endian = f.read(1)
        f.read(1)
        offset = 0
    elif data[0:2] == '\xFF\xD8':
        # it's a JPEG file
        while data[2] == '\xFF' and data[6:10] in ('JFIF', 'JFXX', 'OLYM', 'Phot'):
            length = ord(data[4])*256+ord(data[5])
            f.read(length-8)
            # fake an EXIF beginning of file
            data = '\xFF\x00'+f.read(10)
            fake_exif = 1
        if data[2] == '\xFF' and data[6:10] == 'Exif':
            # detected EXIF header
            offset = f.tell()
            endian = f.read(1)
        else:
            # no EXIF information
            return {}
    else:
        # file format not recognized
        return {}

    # deal with the EXIF info we found
    if debug:
        print {'I': 'Intel', 'M': 'Motorola'}[endian], 'format'
    hdr = EXIF_header(f, endian, offset, fake_exif, strict, debug)
    ifd_list = hdr.list_IFDs()
    ctr = 0
    for i in ifd_list:
        if ctr == 0:
            IFD_name = 'Image'
        elif ctr == 1:
            IFD_name = 'Thumbnail'
            thumb_ifd = i
        else:
            IFD_name = 'IFD %d' % ctr
        if debug:
            print ' IFD %d (%s) at offset %d:' % (ctr, IFD_name, i)
        hdr.dump_IFD(i, IFD_name, stop_tag=stop_tag)
        # EXIF IFD
        exif_off = hdr.tags.get(IFD_name+' ExifOffset')
        if exif_off:
            if debug:
                print ' EXIF SubIFD at offset %d:' % exif_off.values[0]
            hdr.dump_IFD(exif_off.values[0], 'EXIF', stop_tag=stop_tag)
            # Interoperability IFD contained in EXIF IFD
            intr_off = hdr.tags.get('EXIF SubIFD InteroperabilityOffset')
            if intr_off:
                if debug:
                    print ' EXIF Interoperability SubSubIFD at offset %d:' \
                          % intr_off.values[0]
                hdr.dump_IFD(intr_off.values[0], 'EXIF Interoperability',
                             dict=INTR_TAGS, stop_tag=stop_tag)
        # GPS IFD
        gps_off = hdr.tags.get(IFD_name+' GPSInfo')
        if gps_off:
            if debug:
                print ' GPS SubIFD at offset %d:' % gps_off.values[0]
            hdr.dump_IFD(gps_off.values[0], 'GPS', dict=GPS_TAGS, stop_tag=stop_tag)
        ctr += 1

    # extract uncompressed TIFF thumbnail
    thumb = hdr.tags.get('Thumbnail Compression')
    if thumb and thumb.printable == 'Uncompressed TIFF':
        hdr.extract_TIFF_thumbnail(thumb_ifd)

    # JPEG thumbnail (thankfully the JPEG data is stored as a unit)
    thumb_off = hdr.tags.get('Thumbnail JPEGInterchangeFormat')
    if thumb_off:
        f.seek(offset+thumb_off.values[0])
        size = hdr.tags['Thumbnail JPEGInterchangeFormatLength'].values[0]
        hdr.tags['JPEGThumbnail'] = f.read(size)

    # deal with MakerNote contained in EXIF IFD
    # (Some apps use MakerNote tags but do not use a format for which we
    # have a description, do not process these).
    if 'EXIF MakerNote' in hdr.tags and 'Image Make' in hdr.tags and detailed:
        hdr.decode_maker_note()

    # Sometimes in a TIFF file, a JPEG thumbnail is hidden in the MakerNote
    # since it's not allowed in a uncompressed TIFF IFD
    if 'JPEGThumbnail' not in hdr.tags:
        thumb_off=hdr.tags.get('MakerNote JPEGThumbnail')
        if thumb_off:
            f.seek(offset+thumb_off.values[0])
            hdr.tags['JPEGThumbnail']=file.read(thumb_off.field_length)

    return hdr.tags


# show command line usage
def usage(exit_status):
    msg = 'Usage: EXIF.py [OPTIONS] file1 [file2 ...]\n'
    msg += 'Extract EXIF information from digital camera image files.\n\nOptions:\n'
    msg += '-q --quick   Do not process MakerNotes.\n'
    msg += '-t TAG --stop-tag TAG   Stop processing when this tag is retrieved.\n'
    msg += '-s --strict   Run in strict mode (stop on errors).\n'
    msg += '-d --debug   Run in debug mode (display extra info).\n'
    print msg
    sys.exit(exit_status)

# library test/debug function (dump given files)
if __name__ == '__main__':
    import sys
    import getopt

    # parse command line options/arguments
    try:
        opts, args = getopt.getopt(sys.argv[1:], "hqsdt:v", ["help", "quick", "strict", "debug", "stop-tag="])
    except getopt.GetoptError:
        usage(2)
    if args == []:
        usage(2)
    detailed = True
    stop_tag = 'UNDEF'
    debug = False
    strict = False
    for o, a in opts:
        if o in ("-h", "--help"):
            usage(0)
        if o in ("-q", "--quick"):
            detailed = False
        if o in ("-t", "--stop-tag"):
            stop_tag = a
        if o in ("-s", "--strict"):
            strict = True
        if o in ("-d", "--debug"):
            debug = True

    # output info for each file
    for filename in args:
        try:
            file=open(filename, 'rb')
        except:
            print "'%s' is unreadable\n"%filename
            continue
        print filename + ':'
        # get the tags
        data = process_file(file, stop_tag=stop_tag, details=detailed, strict=strict, debug=debug)
        if not data:
            print 'No EXIF information found'
            continue

        x=data.keys()
        x.sort()
        for i in x:
            if i in ('JPEGThumbnail', 'TIFFThumbnail'):
                continue
            try:
                print '   %s (%s): %s' % \
                      (i, FIELD_TYPES[data[i].field_type][2], data[i].printable)
            except:
                print 'error', i, '"', data[i], '"'
        if 'JPEGThumbnail' in data:
            print 'File has JPEG thumbnail'
        print