python读取和写入EXIF信息
什么是EXIF信息呢？
百度百科：Exif是一种图象文件格式，它的数据存储与JPEG格式是完全相同的。实际上Exif格式就是在JPEG格式头部插入了数码照片的信息，包括拍摄时的光圈、快门、白平衡、ISO、焦距、日期时间等各种和拍摄条件以及相机品牌、型号、色彩编码、拍摄时录制的声音以及全球定位系统（GPS）、缩略图等。所有的JPEG文件以字符串“0xFFD8”开头，并以字符串“0xFFD9”结束。文件头中有一系列“0xFF??”格式的字符串，称为“标识”，用来标记JPEG文件的信息段。“0xFFD8”表示图像信息开始，“0xFFD9”表示图像信息结束，这两个标识后面没有信息，而其它标识紧跟一些信息字符。0xFFE0 — 0xFFEF之间的标识符称为“应用标记”，没有被常规JPEG文件利用，Exif正是利用这些信息串记录拍摄信息的。
逛摄影论坛时经常会看到，照片的底部包含很多其他信息，如：曝光度，光圈，焦距，快门，机身等等，这些信息就是EXIF信息，摄影爱好者可以参考这些信息提高自己的摄影技术。本文主要涉及的是如何把信息隐藏到图片中，比如一个电影地址。
首先实现一个最简单的方式，把信息直接添加到图片的头部或者尾部，直接添加到头部由于破坏了图片的数据，所以头部会出现一块黑色的区域比较明显，所以别人一下子就看出来了，效果最差。添加到尾部只是简单的增加了图片的大小，图片的数据区域并没有改变，所以如果信息量不是很大，基本是看不出来的，缺点是传到其他网站时容易被裁剪掉。下面的代码实现了把种子隐藏到图片尾部的1024字节区域。
#coding=utf-8 """ pexif is a module which allows you to view and modify meta-data in JPEG/JFIF/EXIF files. The main way to use this is to create an instance of the JpegFile class. This should be done using one of the static factory methods fromFile, fromString or fromFd. After manipulating the object you can then write it out using one of the writeFile, writeString or writeFd methods. The get_exif() method on JpegFile returns the ExifSegment if one exists. Example: jpeg = pexif.JpegFile.fromFile("foo.jpg") exif = jpeg.get_exif() .... jpeg.writeFile("new.jpg") For photos that don't currently have an exef segment you can specify an argument which will create the exef segment if it doesn't exist. Example: jpeg = pexif.JpegFile.fromFile("foo.jpg") exif = jpeg.get_exif(create=True) .... jpeg.writeFile("new.jpg") The JpegFile class handles file that are formatted in something approach the JPEG specification (ISO/IEC 10918-1) Annex B 'Compressed Data Formats', and JFIF and EXIF standard. a JPEG file is made of a series of segments followed by the image data. In particular it should look something like: [ SOI | <arbitrary segments> | SOS | image data | EOI ] So, the library expects a Start-of-Image marker, followed by an arbitrary number of segment (assuming that a segment has the format: [ <0xFF> <segment-id> <size-byte0> <size-byte1> <data> ] and that there are no gaps between segments. The last segment must be the Start-of-Scan header, and the library assumes that following Start-of-Scan comes the image data, finally followed by the End-of-Image marker. This is probably not sufficient to handle arbitrary files conforming to the JPEG specs, but it should handle files that conform to JFIF or EXIF, as well as files that conform to neither but have both JFIF and EXIF application segment (which is the majority of files in existence!). When writing out files all segment will be written out in the order in which they were read. Any 'unknown' segment will be written out as is. Note: This may or may not corrupt the data. If the segment format relies on absolute references then this library may still corrupt that segment! Can have a JpegFile in two modes: Read Only and Read Write. Read Only mode: trying to access missing elements will result in an AttributeError. Read Write mode: trying to access missing elements will automatically create them. E.g: img.exif.primary.<tagname> .geo .interop .exif.<tagname> .exif.makernote.<tagname> .thumbnail img.flashpix.<...> img.jfif.<tagname> img.xmp E.g: try: print img.exif.tiff.exif.FocalLength except AttributeError: print "No Focal Length data" """ import StringIO import sys from struct import unpack, pack MAX_HEADER_SIZE = 64 * 1024 DELIM = 0xff EOI = 0xd9 SOI_MARKER = chr(DELIM) + '\xd8' EOI_MARKER = chr(DELIM) + '\xd9' EXIF_OFFSET = 0x8769 GPSIFD = 0x8825 TIFF_OFFSET = 6 TIFF_TAG = 0x2a DEBUG = 0 def debug(*debug_string): """Used for print style debugging. Enable by setting the global DEBUG to 1.""" if DEBUG: for each in debug_string: print each, print class DefaultSegment: """DefaultSegment represents a particluar segment of a JPEG file. This class is instantiated by JpegFile when parsing Jpeg files and is not intended to be used directly by the programmer. This base class is used as a default which doesn't know about the internal structure of the segment. Other classes subclass this to provide extra information about a particular segment. """ def __init__(self, marker, fd, data, mode): """The constructor for DefaultSegment takes the marker which identifies the segments, a file object which is currently positioned at the end of the segment. This allows any subclasses to potentially extract extra data from the stream. Data contains the contents of the segment.""" self.marker = marker self.data = data self.mode = mode self.fd = fd assert mode in ["rw", "ro"] if not self.data is None: self.parse_data(data) class InvalidSegment(Exception): """This exception may be raised by sub-classes in cases when they can't correctly identify the segment.""" pass def write(self, fd): """This method is called by JpegFile when writing out the file. It must write out any data in the segment. This shouldn't in general be overloaded by subclasses, they should instead override the get_data() method.""" fd.write('\xff') fd.write(pack('B', self.marker)) data = self.get_data() fd.write(pack('>H', len(data) + 2)) fd.write(data) def get_data(self): """This method is called by write to generate the data for this segment. It should be overloaded by subclasses.""" return self.data def parse_data(self, data): """This method is called be init to parse any data for the segment. It should be overloaded by subclasses rather than overloading __init__""" pass def dump(self, fd): """This is called by JpegFile.dump() to output a human readable representation of the segment. Subclasses should overload this to provide extra information.""" print >> fd, " Section: [%5s] Size: %6d" % \ (jpeg_markers[self.marker][0], len(self.data)) class StartOfScanSegment(DefaultSegment): """The StartOfScan segment needs to be treated specially as the actual image data directly follows this segment, and that data is not included in the size as reported in the segment header. This instances of this class are created by JpegFile and it should not be subclassed. """ def __init__(self, marker, fd, data, mode): DefaultSegment.__init__(self, marker, fd, data, mode) # For SOS we also pull out the actual data img_data = fd.read() # -2 accounts for the EOI marker at the end of the file self.img_data = img_data[:-2] fd.seek(-2, 1) def write(self, fd): """Write segment data to a given file object""" DefaultSegment.write(self, fd) fd.write(self.img_data) def dump(self, fd): """Dump as ascii readable data to a given file object""" print >> fd, " Section: [ SOS] Size: %6d Image data size: %6d" % \ (len(self.data), len(self.img_data)) class ExifType: """The ExifType class encapsulates the data types used in the Exif spec. These should really be called TIFF types probably. This could be replaced by named tuples in python 2.6.""" lookup = {} def __init__(self, type_id, name, size): """Create an ExifType with a given name, size and type_id""" self.id = type_id self.name = name self.size = size ExifType.lookup[type_id] = self BYTE = ExifType(1, "byte", 1).id ASCII = ExifType(2, "ascii", 1).id SHORT = ExifType(3, "short", 2).id LONG = ExifType(4, "long", 4).id RATIONAL = ExifType(5, "rational", 8).id UNDEFINED = ExifType(7, "undefined", 1).id SLONG = ExifType(9, "slong", 4).id SRATIONAL = ExifType(10, "srational", 8).id def exif_type_size(exif_type): """Return the size of a type""" return ExifType.lookup.get(exif_type).size class Rational: """A simple fraction class. Python 2.6 could use the inbuilt Fraction class.""" def __init__(self, num, den): """Create a number fraction num/den.""" self.num = num self.den = den def __repr__(self): """Return a string representation of the fraction.""" return "%s / %s" % (self.num, self.den) def as_tuple(self): """Return the fraction a numerator, denominator tuple.""" return (self.num, self.den) class IfdData: """Base class for IFD""" name = "Generic Ifd" tags = {} embedded_tags = {} def special_handler(self, tag, data): """special_handler method can be over-ridden by subclasses to specially handle the conversion of tags from raw format into Python data types.""" pass def ifd_handler(self, data): """ifd_handler method can be over-ridden by subclasses to specially handle conversion of the Ifd as a whole into a suitable python representation.""" pass def extra_ifd_data(self, offset): """extra_ifd_data method can be over-ridden by subclasses to specially handle conversion of the Python Ifd representation back into a byte stream.""" return "" def has_key(self, key): return self[key] != None def __setattr__(self, name, value): for key, entry in self.tags.items(): if entry[1] == name: self[key] = value self.__dict__[name] = value def __delattr__(self, name): for key, entry in self.tags.items(): if entry[1] == name: del self[key] del self.__dict__[name] def __getattr__(self, name): for key, entry in self.tags.items(): if entry[1] == name: x = self[key] if x is None: raise AttributeError return x for key, entry in self.embedded_tags.items(): if entry[0] == name: if self.has_key(key): return self[key] else: if self.mode == "rw": new = entry[1](self.e, 0, "rw", self.exif_file) self[key] = new return new else: raise AttributeError raise AttributeError, "%s not found.. %s" % (name, self.embedded_tags) def __getitem__(self, key): if type(key) == type(""): try: return self.__getattr__(key) except AttributeError: return None for entry in self.entries: if key == entry[0]: if entry[1] == ASCII and not entry[2] is None: return entry[2].strip('\0') else: return entry[2] return None def __delitem__(self, key): if type(key) == type(""): try: return self.__delattr__(key) except AttributeError: return None for entry in self.entries: if key == entry[0]: self.entries.remove(entry) def __setitem__(self, key, value): if type(key) == type(""): return self.__setattr__(key, value) found = 0 if len(self.tags[key]) < 3: raise "Error: Tags aren't set up correctly, should have tag type." if self.tags[key][2] == ASCII: if not value is None and not value.endswith('\0'): value = value + '\0' for i in range(len(self.entries)): if key == self.entries[i][0]: found = 1 entry = list(self.entries[i]) if value is None: del self.entries[i] else: entry[2] = value self.entries[i] = tuple(entry) break if not found: # Find type... # Not quite enough yet... self.entries.append((key, self.tags[key][2], value)) return def __init__(self, e, offset, exif_file, mode, data = None): self.exif_file = exif_file self.mode = mode self.e = e self.entries = [] if data is None: return num_entries = unpack(e + 'H', data[offset:offset+2])[0] next = unpack(e + "I", data[offset+2+12*num_entries: offset+2+12*num_entries+4])[0] debug("OFFSET %s - %s" % (offset, next)) for i in range(num_entries): start = (i * 12) + 2 + offset debug("START: ", start) entry = unpack(e + "HHII", data[start:start+12]) tag, exif_type, components, the_data = entry debug("%s %s %s %s %s" % (hex(tag), exif_type, exif_type_size(exif_type), components, the_data)) byte_size = exif_type_size(exif_type) * components if tag in self.embedded_tags: actual_data = self.embedded_tags[tag][1](e, the_data, exif_file, self.mode, data) else: if byte_size > 4: debug(" ...offset %s" % the_data) the_data = data[the_data:the_data+byte_size] else: the_data = data[start+8:start+8+byte_size] if exif_type == BYTE or exif_type == UNDEFINED: actual_data = list(the_data) elif exif_type == ASCII: if the_data[-1] != '\0': actual_data = the_data + '\0' #raise JpegFile.InvalidFile("ASCII tag '%s' not # NULL-terminated: %s [%s]" % (self.tags.get(tag, # (hex(tag), 0))[0], the_data, map(ord, the_data))) #print "ASCII tag '%s' not NULL-terminated: # %s [%s]" % (self.tags.get(tag, (hex(tag), 0))[0], # the_data, map(ord, the_data)) actual_data = the_data elif exif_type == SHORT: actual_data = list(unpack(e + ("H" * components), the_data)) elif exif_type == LONG: actual_data = list(unpack(e + ("I" * components), the_data)) elif exif_type == SLONG: actual_data = list(unpack(e + ("i" * components), the_data)) elif exif_type == RATIONAL or exif_type == SRATIONAL: if exif_type == RATIONAL: t = "II" else: t = "ii" actual_data = [] for i in range(components): actual_data.append(Rational(*unpack(e + t, the_data[i*8: i*8+8]))) else: raise "Can't handle this" if (byte_size > 4): debug("%s" % actual_data) self.special_handler(tag, actual_data) entry = (tag, exif_type, actual_data) self.entries.append(entry) debug("%-40s %-10s %6d %s" % (self.tags.get(tag, (hex(tag), 0))[0], ExifType.lookup[exif_type], components, actual_data)) self.ifd_handler(data) def isifd(self, other): """Return true if other is an IFD""" return issubclass(other.__class__, IfdData) def getdata(self, e, offset, last = 0): data_offset = offset+2+len(self.entries)*12+4 output_data = "" out_entries = [] # Add any specifc data for the particular type extra_data = self.extra_ifd_data(data_offset) data_offset += len(extra_data) output_data += extra_data for tag, exif_type, the_data in self.entries: magic_type = exif_type if (self.isifd(the_data)): debug("-> Magic..") sub_data, next_offset = the_data.getdata(e, data_offset, 1) the_data = [data_offset] debug("<- Magic", next_offset, data_offset, len(sub_data), data_offset + len(sub_data)) data_offset += len(sub_data) assert(next_offset == data_offset) output_data += sub_data magic_type = exif_type if exif_type != 4: magic_components = len(sub_data) else: magic_components = 1 exif_type = 4 # LONG byte_size = 4 components = 1 else: magic_components = components = len(the_data) byte_size = exif_type_size(exif_type) * components if exif_type == BYTE or exif_type == UNDEFINED: actual_data = "".join(the_data) elif exif_type == ASCII: actual_data = the_data elif exif_type == SHORT: actual_data = pack(e + ("H" * components), *the_data) elif exif_type == LONG: actual_data = pack(e + ("I" * components), *the_data) elif exif_type == SLONG: actual_data = pack(e + ("i" * components), *the_data) elif exif_type == RATIONAL or exif_type == SRATIONAL: if exif_type == RATIONAL: t = "II" else: t = "ii" actual_data = "" for i in range(components): actual_data += pack(e + t, *the_data[i].as_tuple()) else: raise "Can't handle this", exif_type if (byte_size) > 4: output_data += actual_data actual_data = pack(e + "I", data_offset) data_offset += byte_size else: actual_data = actual_data + '\0' * (4 - len(actual_data)) out_entries.append((tag, magic_type, magic_components, actual_data)) data = pack(e + 'H', len(self.entries)) for entry in out_entries: data += pack(self.e + "HHI", *entry[:3]) data += entry[3] next_offset = data_offset if last: data += pack(self.e + "I", 0) else: data += pack(self.e + "I", next_offset) data += output_data assert (next_offset == offset+len(data)) return data, next_offset def dump(self, f, indent = ""): """Dump the IFD file""" print >> f, indent + "<--- %s start --->" % self.name for entry in self.entries: tag, exif_type, data = entry if exif_type == ASCII: data = data.strip('\0') if (self.isifd(data)): data.dump(f, indent + " ") else: if data and len(data) == 1: data = data[0] print >> f, indent + " %-40s %s" % \ (self.tags.get(tag, (hex(tag), 0))[0], data) print >> f, indent + "<--- %s end --->" % self.name class IfdInterop(IfdData): name = "Interop" tags = { # Interop stuff 0x0001: ("Interoperability index", "InteroperabilityIndex"), 0x0002: ("Interoperability version", "InteroperabilityVersion"), 0x1000: ("Related image file format", "RelatedImageFileFormat"), 0x1001: ("Related image file width", "RelatedImageFileWidth"), 0x1002: ("Related image file length", "RelatedImageFileLength"), } class CanonIFD(IfdData): tags = { 0x0006: ("Image Type", "ImageType"), 0x0007: ("Firmware Revision", "FirmwareRevision"), 0x0008: ("Image Number", "ImageNumber"), 0x0009: ("Owner Name", "OwnerName"), 0x000c: ("Camera serial number", "SerialNumber"), 0x000f: ("Customer functions", "CustomerFunctions") } name = "Canon" class FujiIFD(IfdData): tags = { 0x0000: ("Note version", "NoteVersion"), 0x1000: ("Quality", "Quality"), 0x1001: ("Sharpness", "Sharpness"), 0x1002: ("White balance", "WhiteBalance"), 0x1003: ("Color", "Color"), 0x1004: ("Tone", "Tone"), 0x1010: ("Flash mode", "FlashMode"), 0x1011: ("Flash strength", "FlashStrength"), 0x1020: ("Macro", "Macro"), 0x1021: ("Focus mode", "FocusMode"), 0x1030: ("Slow sync", "SlowSync"), 0x1031: ("Picture mode", "PictureMode"), 0x1100: ("Motor or bracket", "MotorOrBracket"), 0x1101: ("Sequence number", "SequenceNumber"), 0x1210: ("FinePix Color", "FinePixColor"), 0x1300: ("Blur warning", "BlurWarning"), 0x1301: ("Focus warning", "FocusWarning"), 0x1302: ("AE warning", "AEWarning") } name = "FujiFilm" def getdata(self, e, offset, last = 0): pre_data = "FUJIFILM" pre_data += pack("<I", 12) data, next_offset = IfdData.getdata(self, e, 12, last) return pre_data + data, next_offset + offset def ifd_maker_note(e, offset, exif_file, mode, data): """Factory function for creating MakeNote entries""" if exif_file.make == "Canon": # Canon maker note appears to always be in Little-Endian return CanonIFD('<', offset, exif_file, mode, data) elif exif_file.make == "FUJIFILM": # The FujiFILM maker note is special. # See http://www.ozhiker.com/electronics/pjmt/jpeg_info/fujifilm_mn.html # First it has an extra header header = data[offset:offset+8] # Which should be FUJIFILM if header != "FUJIFILM": raise JpegFile.InvalidFile("This is FujiFilm JPEG. " \ "Expecting a makernote header "\ "<FUJIFILM>. Got <%s>." % header) # The it has its own offset ifd_offset = unpack("<I", data[offset+8:offset+12])[0] # and it is always litte-endian e = "<" # and the data is referenced from the start the Ifd data, not the # TIFF file. ifd_data = data[offset:] return FujiIFD(e, ifd_offset, exif_file, mode, ifd_data) else: raise JpegFile.InvalidFile("Unknown maker: %s. Can't "\ "currently handle this." % exif_file.make) class IfdGPS(IfdData): name = "GPS" tags = { 0x0: ("GPS tag version", "GPSVersionID", BYTE, 4), 0x1: ("North or South Latitude", "GPSLatitudeRef", ASCII, 2), 0x2: ("Latitude", "GPSLatitude", RATIONAL, 3), 0x3: ("East or West Longitude", "GPSLongitudeRef", ASCII, 2), 0x4: ("Longitude", "GPSLongitude", RATIONAL, 3), 0x5: ("Altitude reference", "GPSAltitudeRef", BYTE, 1), 0x6: ("Altitude", "GPSAltitude", RATIONAL, 1) } def __init__(self, e, offset, exif_file, mode, data = None): IfdData.__init__(self, e, offset, exif_file, mode, data) if data is None: self.GPSVersionID = ['\x02', '\x02', '\x00', '\x00'] class IfdExtendedEXIF(IfdData): tags = { # Exif IFD Attributes # A. Tags relating to version 0x9000: ("Exif Version", "ExifVersion"), 0xA000: ("Supported Flashpix version", "FlashpixVersion"), # B. Tag relating to Image Data Characteristics 0xA001: ("Color Space Information", "ColorSpace"), # C. Tags relating to Image Configuration 0x9101: ("Meaning of each component", "ComponentConfiguration"), 0x9102: ("Image compression mode", "CompressedBitsPerPixel"), 0xA002: ("Valid image width", "PixelXDimension"), 0xA003: ("Valid image height", "PixelYDimension"), # D. Tags relatin to User informatio 0x927c: ("Manufacturer notes", "MakerNote"), 0x9286: ("User comments", "UserComment"), # E. Tag relating to related file information 0xA004: ("Related audio file", "RelatedSoundFile"), # F. Tags relating to date and time 0x9003: ("Date of original data generation", "DateTimeOriginal", ASCII), 0x9004: ("Date of digital data generation", "DateTimeDigitized", ASCII), 0x9290: ("DateTime subseconds", "SubSecTime"), 0x9291: ("DateTime original subseconds", "SubSecTimeOriginal"), 0x9292: ("DateTime digitized subseconds", "SubSecTimeDigitized"), # G. Tags relating to Picture taking conditions 0x829a: ("Exposure Time", "ExposureTime"), 0x829d: ("F Number", "FNumber"), 0x8822: ("Exposure Program", "ExposureProgram"), 0x8824: ("Spectral Sensitivity", "SpectralSensitivity"), 0x8827: ("ISO Speed Rating", "ISOSpeedRatings"), 0x8829: ("Optoelectric conversion factor", "OECF"), 0x9201: ("Shutter speed", "ShutterSpeedValue"), 0x9202: ("Aperture", "ApertureValue"), 0x9203: ("Brightness", "BrightnessValue"), 0x9204: ("Exposure bias", "ExposureBiasValue"), 0x9205: ("Maximum lens apeture", "MaxApertureValue"), 0x9206: ("Subject Distance", "SubjectDistance"), 0x9207: ("Metering mode", "MeteringMode"), 0x9208: ("Light mode", "LightSource"), 0x9209: ("Flash", "Flash"), 0x920a: ("Lens focal length", "FocalLength"), 0x9214: ("Subject area", "Subject area"), 0xa20b: ("Flash energy", "FlashEnergy"), 0xa20c: ("Spatial frequency results", "SpatialFrquencyResponse"), 0xa20e: ("Focal plane X resolution", "FocalPlaneXResolution"), 0xa20f: ("Focal plane Y resolution", "FocalPlaneYResolution"), 0xa210: ("Focal plane resolution unit", "FocalPlaneResolutionUnit"), 0xa214: ("Subject location", "SubjectLocation"), 0xa215: ("Exposure index", "ExposureIndex"), 0xa217: ("Sensing method", "SensingMethod"), 0xa300: ("File source", "FileSource"), 0xa301: ("Scene type", "SceneType"), 0xa302: ("CFA pattern", "CFAPattern"), 0xa401: ("Customer image processing", "CustomerRendered"), 0xa402: ("Exposure mode", "ExposureMode"), 0xa403: ("White balance", "WhiteBalance"), 0xa404: ("Digital zoom ratio", "DigitalZoomRation"), 0xa405: ("Focal length in 35mm film", "FocalLengthIn35mmFilm"), 0xa406: ("Scene capture type", "SceneCaptureType"), 0xa407: ("Gain control", "GainControl"), 0xa40a: ("Sharpness", "Sharpness"), 0xa40c: ("Subject distance range", "SubjectDistanceRange"), # H. Other tags 0xa420: ("Unique image ID", "ImageUniqueID"), } embedded_tags = { 0x927c: ("MakerNote", ifd_maker_note), } name = "Extended EXIF" class IfdTIFF(IfdData): """ """ tags = { # Private Tags 0x8769: ("Exif IFD Pointer", "ExifOffset", LONG), 0xA005: ("Interoparability IFD Pointer", "InteroparabilityIFD", LONG), 0x8825: ("GPS Info IFD Pointer", "GPSIFD", LONG), # TIFF stuff used by EXIF # A. Tags relating to image data structure 0x100: ("Image width", "ImageWidth", LONG), 0x101: ("Image height", "ImageHeight", LONG), 0x102: ("Number of bits per component", "BitsPerSample", SHORT), 0x103: ("Compression Scheme", "Compression", SHORT), 0x106: ("Pixel Composition", "PhotometricInterpretion", SHORT), 0x112: ("Orientation of image", "Orientation", SHORT), 0x115: ("Number of components", "SamplesPerPixel", SHORT), 0x11c: ("Image data arrangement", "PlanarConfiguration", SHORT), 0x212: ("Subsampling ration of Y to C", "YCbCrSubsampling", SHORT), 0x213: ("Y and C positioning", "YCbCrCoefficients", SHORT), 0x11a: ("X Resolution", "XResolution", RATIONAL), 0x11b: ("Y Resolution", "YResolution", RATIONAL), 0x128: ("Unit of X and Y resolution", "ResolutionUnit", SHORT), # B. Tags relating to recording offset 0x111: ("Image data location", "StripOffsets", LONG), 0x116: ("Number of rows per strip", "RowsPerStrip", LONG), 0x117: ("Bytes per compressed strip", "StripByteCounts", LONG), 0x201: ("Offset to JPEG SOI", "JPEGInterchangeFormat", LONG), 0x202: ("Bytes of JPEG data", "JPEGInterchangeFormatLength", LONG), # C. Tags relating to image data characteristics # D. Other tags 0x132: ("File change data and time", "DateTime", ASCII), 0x10e: ("Image title", "ImageDescription", ASCII), 0x10f: ("Camera Make", "Make", ASCII), 0x110: ("Camera Model", "Model", ASCII), 0x131: ("Camera Software", "Software", ASCII), 0x13B: ("Artist", "Artist", ASCII), 0x8298: ("Copyright holder", "Copyright", ASCII), } embedded_tags = { 0xA005: ("Interoperability", IfdInterop), EXIF_OFFSET: ("ExtendedEXIF", IfdExtendedEXIF), 0x8825: ("GPS", IfdGPS), } name = "TIFF Ifd" def special_handler(self, tag, data): if self.tags[tag][1] == "Make": self.exif_file.make = data.strip('\0') def new_gps(self): if self.has_key(GPSIFD): raise ValueError, "Already have a GPS Ifd" assert self.mode == "rw" gps = IfdGPS(self.e, 0, self.mode, self.exif_file) self[GPSIFD] = gps return gps class IfdThumbnail(IfdTIFF): name = "Thumbnail" def ifd_handler(self, data): size = None offset = None for (tag, exif_type, val) in self.entries: if (tag == 0x201): offset = val[0] if (tag == 0x202): size = val[0] if size is None or offset is None: raise JpegFile.InvalidFile("Thumbnail doesn't have an offset "\ "and/or size") self.jpeg_data = data[offset:offset+size] if len(self.jpeg_data) != size: raise JpegFile.InvalidFile("Not enough data for JPEG thumbnail."\ "Wanted: %d got %d" % (size, len(self.jpeg_data))) def extra_ifd_data(self, offset): for i in range(len(self.entries)): entry = self.entries[i] if entry[0] == 0x201: # Print found field and updating new_entry = (entry[0], entry[1], [offset]) self.entries[i] = new_entry return self.jpeg_data class ExifSegment(DefaultSegment): """ExifSegment encapsulates the Exif data stored in a JpegFile. An ExifSegment contains two Image File Directories (IFDs). One is attribute information and the other is a thumbnail. This module doesn't provide any useful functions for manipulating the thumbnail, but does provide a get_attributes returns an AttributeIfd instances which allows you to manipulate the attributes in a Jpeg file.""" def __init__(self, marker, fd, data, mode): self.ifds = [] self.e = '<' self.tiff_endian = 'II' DefaultSegment.__init__(self, marker, fd, data, mode) def parse_data(self, data): """Overloads the DefaultSegment method to parse the data of this segment. Can raise InvalidFile if we don't get what we expect.""" exif = unpack("6s", data[:6])[0] exif = exif.strip('\0') if (exif != "Exif"): raise self.InvalidSegment("Bad Exif Marker. Got <%s>, "\ "expecting <Exif>" % exif) tiff_data = data[TIFF_OFFSET:] data = None # Don't need or want data for now on.. self.tiff_endian = tiff_data[:2] if self.tiff_endian == "II": self.e = "<" elif self.tiff_endian == "MM": self.e = ">" else: raise JpegFile.InvalidFile("Bad TIFF endian header. Got <%s>, " "expecting <II> or <MM>" % self.tiff_endian) tiff_tag, tiff_offset = unpack(self.e + 'HI', tiff_data[2:8]) if (tiff_tag != TIFF_TAG): raise JpegFile.InvalidFile("Bad TIFF tag. Got <%x>, expecting "\ "<%x>" % (tiff_tag, TIFF_TAG)) # Ok, the header parse out OK. Now we parse the IFDs contained in # the APP1 header. # We use this loop, even though we can really only expect and support # two IFDs, the Attribute data and the Thumbnail data offset = tiff_offset count = 0 while offset: count += 1 num_entries = unpack(self.e + 'H', tiff_data[offset:offset+2])[0] start = 2 + offset + (num_entries*12) if (count == 1): ifd = IfdTIFF(self.e, offset, self, self.mode, tiff_data) elif (count == 2): ifd = IfdThumbnail(self.e, offset, self, self.mode, tiff_data) else: raise JpegFile.InvalidFile() self.ifds.append(ifd) # Get next offset offset = unpack(self.e + "I", tiff_data[start:start+4])[0] def dump(self, fd): print >> fd, " Section: [ EXIF] Size: %6d" % \ (len(self.data)) for ifd in self.ifds: ifd.dump(fd) def get_data(self): ifds_data = "" next_offset = 8 for ifd in self.ifds: debug("OUT IFD") new_data, next_offset = ifd.getdata(self.e, next_offset, ifd == self.ifds[-1]) ifds_data += new_data data = "" data += "Exif\0\0" data += self.tiff_endian data += pack(self.e + "HI", 42, 8) data += ifds_data return data def get_primary(self, create=False): """Return the attributes image file descriptor. If it doesn't exit return None, unless create is True in which case a new descriptor is created.""" if len(self.ifds) > 0: return self.ifds[0] else: if create: assert self.mode == "rw" new_ifd = IfdTIFF(self.e, None, self, "rw") self.ifds.insert(0, new_ifd) return new_ifd else: return None def _get_property(self): if self.mode == "rw": return self.get_primary(True) else: primary = self.get_primary() if primary is None: raise AttributeError return primary primary = property(_get_property) jpeg_markers = { 0xc0: ("SOF0", []), 0xc2: ("SOF2", []), 0xc4: ("DHT", []), 0xda: ("SOS", [StartOfScanSegment]), 0xdb: ("DQT", []), 0xdd: ("DRI", []), 0xe0: ("APP0", []), 0xe1: ("APP1", [ExifSegment]), 0xe2: ("APP2", []), 0xe3: ("APP3", []), 0xe4: ("APP4", []), 0xe5: ("APP5", []), 0xe6: ("APP6", []), 0xe7: ("APP7", []), 0xe8: ("APP8", []), 0xe9: ("APP9", []), 0xea: ("APP10", []), 0xeb: ("APP11", []), 0xec: ("APP12", []), 0xed: ("APP13", []), 0xee: ("APP14", []), 0xef: ("APP15", []), 0xfe: ("COM", []), } APP1 = 0xe1 class JpegFile: """JpegFile object. You should create this using one of the static methods fromFile, fromString or fromFd. The JpegFile object allows you to examine and modify the contents of the file. To write out the data use one of the methods writeFile, writeString or writeFd. To get an ASCII dump of the data in a file use the dump method.""" def fromFile(filename, mode="rw"): """Return a new JpegFile object from a given filename.""" return JpegFile(open(filename, "rb"), filename=filename, mode=mode) fromFile = staticmethod(fromFile) def fromString(str, mode="rw"): """Return a new JpegFile object taking data from a string.""" return JpegFile(StringIO.StringIO(str), "from buffer", mode=mode) fromString = staticmethod(fromString) def fromFd(fd, mode="rw"): """Return a new JpegFile object taking data from a file object.""" return JpegFile(fd, None, mode=mode) fromFd = staticmethod(fromFd) class InvalidFile(Exception): """This exception is raised if a given file is not able to be parsed.""" pass class NoSection(Exception): """This exception is raised if a section is unable to be found.""" pass def __init__(self, input, filename=None, mode="rw"): """JpegFile Constructor. input is a file object, and filename is a string used to name the file. (filename is used only for display functions). You shouldn't use this function directly, but rather call one of the static methods fromFile, fromString or fromFd.""" self.filename = filename self.mode = mode # input is the file descriptor soi_marker = input.read(len(SOI_MARKER)) # The very first thing should be a start of image marker if (soi_marker != SOI_MARKER): raise self.InvalidFile("Error reading soi_marker. Got <%s> "\ "should be <%s>" % (soi_marker, SOI_MARKER)) # Now go through and find all the blocks of data segments = [] while 1: head = input.read(2) delim, mark = unpack(">BB", head) if (delim != DELIM): raise self.InvalidFile("Error, expecting delmiter. "\ "Got <%s> should be <%s>" % (delim, DELIM)) if mark == EOI: # Hit end of image marker, game-over! break head2 = input.read(2) size = unpack(">H", head2)[0] data = input.read(size-2) possible_segment_classes = jpeg_markers[mark][1] + [DefaultSegment] # Try and find a valid segment class to handle # this data for segment_class in possible_segment_classes: try: # Note: Segment class may modify the input file # descriptor. This is expected. attempt = segment_class(mark, input, data, self.mode) segments.append(attempt) break except DefaultSegment.InvalidSegment: # It wasn't this one so we try the next type. # DefaultSegment will always work. continue self._segments = segments def writeString(self): """Write the JpegFile out to a string. Returns a string.""" f = StringIO.StringIO() self.writeFd(f) return f.getvalue() def writeFile(self, filename): """Write the JpegFile out to a file named filename.""" output = open(filename, "wb") self.writeFd(output) def writeFd(self, output): """Write the JpegFile out on the file object output.""" output.write(SOI_MARKER) for segment in self._segments: segment.write(output) output.write(EOI_MARKER) def dump(self, f = sys.stdout): """Write out ASCII representation of the file on a given file object. Output default to stdout.""" print >> f, "<Dump of JPEG %s>" % self.filename for segment in self._segments: segment.dump(f) def get_exif(self, create=False): """get_exif returns a ExifSegment if one exists for this file. If the file does not have an exif segment and the create is false, then return None. If create is true, a new exif segment is added to the file and returned.""" for segment in self._segments: if segment.__class__ == ExifSegment: return segment if create: return self.add_exif() else: return None def add_exif(self): """add_exif adds a new ExifSegment to a file, and returns it. When adding an EXIF segment is will add it at the start of the list of segments.""" assert self.mode == "rw" new_segment = ExifSegment(APP1, None, None, "rw") self._segments.insert(0, new_segment) return new_segment def _get_exif(self): """Exif Attribute property""" if self.mode == "rw": return self.get_exif(True) else: exif = self.get_exif(False) if exif is None: raise AttributeError return exif exif = property(_get_exif) def get_geo(self): """Return a tuple of (latitude, longitude).""" def convert(x): (deg, min, sec) = x return (float(deg.num) / deg.den) + \ (1/60.0 * float(min.num) / min.den) + \ (1/3600.0 * float(sec.num) / sec.den) if not self.exif.primary.has_key(GPSIFD): raise self.NoSection, "File %s doesn't have a GPS section." % \ self.filename gps = self.exif.primary.GPS lat = convert(gps.GPSLatitude) lng = convert(gps.GPSLongitude) if gps.GPSLatitudeRef == "S": lat = -lat if gps.GPSLongitudeRef == "W": lng = -lng return lat, lng SEC_DEN = 50000000 def _parse(val): sign = 1 if val < 0: val = -val sign = -1 deg = int(val) other = (val - deg) * 60 minutes = int(other) secs = (other - minutes) * 60 secs = long(secs * JpegFile.SEC_DEN) return (sign, deg, minutes, secs) _parse = staticmethod(_parse) def set_geo(self, lat, lng): """Set the GeoLocation to a given lat and lng""" if self.mode != "rw": raise RWError gps = self.exif.primary.GPS sign, deg, min, sec = JpegFile._parse(lat) ref = "N" if sign < 0: ref = "S" gps.GPSLatitudeRef = ref gps.GPSLatitude = [Rational(deg, 1), Rational(min, 1), Rational(sec, JpegFile.SEC_DEN)] sign, deg, min, sec = JpegFile._parse(lng) ref = "E" if sign < 0: ref = "W" gps.GPSLongitudeRef = ref gps.GPSLongitude = [Rational(deg, 1), Rational(min, 1), Rational(sec, JpegFile.SEC_DEN)] def set_copyright(self, copyright): """Set the copyright to a given copyright string""" if self.mode != "rw": raise RWError self.exif.primary.Copyright = copyright def read_copyright(imgFile): jpeg = JpegFile.fromFd(imgFile) exif = jpeg.get_exif() print exif.get_primary().Copyright.decode("gbk") if __name__ == "__main__": import StringIO import sys reload(sys) sys.setdefaultencoding('utf-8') f = open("test.jpg") read_copyright(f) f.seek(0) jpeg = JpegFile.fromFd(f) copyright = u"qvod://fuck小日本".encode("gbk") jpeg.set_copyright(copyright) buf = StringIO.StringIO() jpeg.writeFd(buf) buf.seek(0) read_copyright(buf) f.close()转载请注明来自：Alex Zhou，本文链接：http://codingnow.cn/python/612.html