fabio.TiffIO — FabIO 0.1.3 documentation

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# Source code for fabio.TiffIO

    #/*##########################################################################
    # Copyright (C) 2012 European Synchrotron Radiation Facility
    #
    # This file is part of the PyMca X-ray Fluorescence Toolkit developed at
    # the ESRF by the Software group.
    #
    # This file is free software; you can redistribute it and/or modify it
    # under the terms of the GNU Lesser General Public License as published by the Free
    # Software Foundation; either version 2 of the License, or (at your option)
    # any later version.
    #
    # PyMca is distributed in the hope that it will be useful, but WITHOUT ANY
    # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
    # FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
    # details.
    #
    #############################################################################*/
    __author__ = "V.A. Sole - ESRF Data Analysis"
    __revision__ = 1501

    import sys
    import os
    import struct
    import numpy

    DEBUG = 0
    ALLOW_MULTIPLE_STRIPS = False

    TAG_ID = { 256:"NumberOfColumns", # S or L ImageWidth
                257:"NumberOfRows", # S or L ImageHeight
                258:"BitsPerSample", # S Number of bits per component
                259:"Compression", # SHORT (1 - NoCompression, ...
                262:"PhotometricInterpretation", # SHORT (0 - WhiteIsZero, 1 -BlackIsZero, 2 - RGB, 3 - Palette color
                270:"ImageDescription", # ASCII
                273:"StripOffsets", # S or L, for each strip, the byte offset of the strip
                278:"RowsPerStrip", # S or L, number of rows in each back may be not for the last
                279:"StripByteCounts", # S or L, The number of bytes in the strip AFTER any compression
                305:"Software", # ASCII
                306:"Date", # ASCII
                320:"Colormap", # Colormap of Palette-color Images
                339:"SampleFormat", # SHORT Interpretation of data in each pixel
                }

    #TILES ARE TO BE SUPPORTED TOO ...
    TAG_NUMBER_OF_COLUMNS = 256
    TAG_NUMBER_OF_ROWS = 257
    TAG_BITS_PER_SAMPLE = 258
    TAG_PHOTOMETRIC_INTERPRETATION = 262
    TAG_COMPRESSION = 259
    TAG_IMAGE_DESCRIPTION = 270
    TAG_STRIP_OFFSETS = 273
    TAG_ROWS_PER_STRIP = 278
    TAG_STRIP_BYTE_COUNTS = 279
    TAG_SOFTWARE = 305
    TAG_DATE = 306
    TAG_COLORMAP = 320
    TAG_SAMPLE_FORMAT = 339

    FIELD_TYPE = {1:('BYTE', "B"),
                   2:('ASCII', "s"), #string ending with binary zero
                   3:('SHORT', "H"),
                   4:('LONG', "I"),
                   5:('RATIONAL', "II"),
                   6:('SBYTE', "b"),
                   7:('UNDEFINED', "B"),
                   8:('SSHORT', "h"),
                   9:('SLONG', "i"),
                   10:('SRATIONAL', "ii"),
                   11:('FLOAT', "f"),
                   12:('DOUBLE', "d")}

    FIELD_TYPE_OUT = { 'B':   1,
                       's':   2,
                       'H':   3,
                       'I':   4,
                       'II':  5,
                       'b':   6,
                       'h':   8,
                       'i':   9,
                       'ii': 10,
                       'f':  11,
                       'd':  12}

    #sample formats (http://www.awaresystems.be/imaging/tiff/tiffflags/sampleformat.html)
    SAMPLE_FORMAT_UINT = 1
    SAMPLE_FORMAT_INT = 2
    SAMPLE_FORMAT_FLOAT = 3   #floating point
    SAMPLE_FORMAT_VOID = 4   #undefined data, usually assumed UINT
    SAMPLE_FORMAT_COMPLEXINT = 5
    SAMPLE_FORMAT_COMPLEXIEEEFP = 6

    class TiffIO(object):
        def __init__(self, filename, mode=None, cache_length=20, mono_output=False):
            if mode is None:
                mode = 'rb'
            if 'b' not in mode:
                mode = mode + 'b'
            if 'a' in mode.lower():
                raise IOError("Mode %s makes no sense on TIFF files. Consider 'rb+'" % mode)
            if ('w' in mode):
                if '+' not in mode:
                    mode += '+'
            #if isinstance(filename, file): #does not work in python 3
            if hasattr(filename, "seek"):
                fd = filename
                self._access = None
            else:
                #the b is needed for windows and python 3
                fd = open(filename, mode)
                self._access = mode

            self._initInternalVariables(fd)
            self._maxImageCacheLength = cache_length
            self._forceMonoOutput = mono_output

        def _initInternalVariables(self, fd=None):
            if fd is None:
                fd = self.fd
            else:
                self.fd = fd
            # read the order
            fd.seek(0)
            order = fd.read(2).decode()
            if len(order):
                if order == "II":
                    #intel, little endian
                    fileOrder = "little"
                    self._structChar = '<'
                elif order == "MM":
                    #motorola, high endian
                    fileOrder = "big"
                    self._structChar = '>'
                else:
                    raise IOError("File is not a Mar CCD file, nor a TIFF file")
                a = fd.read(2)
                fortyTwo = struct.unpack(self._structChar + "H", a)[0]
                if fortyTwo != 42:
                    raise IOError("Invalid TIFF version %d" % fortyTwo)
                else:
                    if DEBUG:
                        print("VALID TIFF VERSION")
                if sys.byteorder != fileOrder:
                    swap = True
                else:
                    swap = False
            else:
                if sys.byteorder == "little":
                    self._structChar = '<'
                else:
                    self._structChar = '>'
                swap = False
            self._swap = swap
            self._IFD = []
            self._imageDataCacheIndex = []
            self._imageDataCache = []
            self._imageInfoCacheIndex = []
            self._imageInfoCache = []
            self.getImageFileDirectories(fd)

        def __makeSureFileIsOpen(self):
            if not self.fd.closed:
                return
            if DEBUG:
                print("Reopening closed file")
            fileName = self.fd.name
            if self._access is None:
                #we do not own the file
                #open in read mode
                newFile = open(fileName, 'rb')
            else:
                newFile = open(fileName, self._access)
            self.fd = newFile

        def __makeSureFileIsClosed(self):
            if self._access is None:
                #we do not own the file
                if DEBUG:
                    print("Not closing not owned file")
                return

            if not self.fd.closed:
                self.fd.close()

        def getNumberOfImages(self):
            #update for the case someone has done anything?
            self._updateIFD()
            return len(self._IFD)

        def _updateIFD(self):
            self.__makeSureFileIsOpen()
            self.getImageFileDirectories()
            self.__makeSureFileIsClosed()

        def getImageFileDirectories(self, fd=None):
            if fd is None:
                fd = self.fd
            else:
                self.fd = fd
            st = self._structChar
            fd.seek(4)
            self._IFD = []
            nImages = 0
            fmt = st + 'I'
            inStr = fd.read(struct.calcsize(fmt))
            if not len(inStr):
                offsetToIFD = 0
            else:
                offsetToIFD = struct.unpack(fmt, inStr)[0]
            if DEBUG:
                print("Offset to first IFD = %d" % offsetToIFD)
            while offsetToIFD != 0:
                self._IFD.append(offsetToIFD)
                nImages += 1
                fd.seek(offsetToIFD)
                fmt = st + 'H'
                numberOfDirectoryEntries = struct.unpack(fmt, fd.read(struct.calcsize(fmt)))[0]
                if DEBUG:
                    print("Number of directory entries = %d" % numberOfDirectoryEntries)

                fmt = st + 'I'
                fd.seek(offsetToIFD + 2 + 12 * numberOfDirectoryEntries)
                offsetToIFD = struct.unpack(fmt, fd.read(struct.calcsize(fmt)))[0]
                if DEBUG:
                    print("Next Offset to IFD = %d" % offsetToIFD)
                #offsetToIFD = 0
            if DEBUG:
                print("Number of images found = %d" % nImages)
            return nImages

        def _parseImageFileDirectory(self, nImage):
            offsetToIFD = self._IFD[nImage]
            st = self._structChar
            fd = self.fd
            fd.seek(offsetToIFD)
            fmt = st + 'H'
            numberOfDirectoryEntries = struct.unpack(fmt, fd.read(struct.calcsize(fmt)))[0]
            if DEBUG:
                print("Number of directory entries = %d" % numberOfDirectoryEntries)

            fmt = st + 'HHI4s'
            tagIDList = []
            fieldTypeList = []
            nValuesList = []
            valueOffsetList = []
            for i in range(numberOfDirectoryEntries):
                tagID, fieldType, nValues, valueOffset = struct.unpack(fmt, fd.read(12))
                tagIDList.append(tagID)
                fieldTypeList.append(fieldType)
                nValuesList.append(nValues)
                if nValues == 1:
                    ftype, vfmt = FIELD_TYPE[fieldType]
                    if ftype not in ['ASCII', 'RATIONAL', 'SRATIONAL']:
                        vfmt = st + vfmt
                        actualValue = struct.unpack(vfmt, valueOffset[0: struct.calcsize(vfmt)])[0]
                        valueOffsetList.append(actualValue)
                    else:
                        valueOffsetList.append(valueOffset)
                elif (nValues < 5) and (fieldType == 2):
                    ftype, vfmt = FIELD_TYPE[fieldType]
                    vfmt = st + "%d%s" % (nValues, vfmt)
                    actualValue = struct.unpack(vfmt, valueOffset[0: struct.calcsize(vfmt)])[0]
                    valueOffsetList.append(actualValue)
                else:
                    valueOffsetList.append(valueOffset)
                if DEBUG:
                    if tagID in TAG_ID:
                        print("tagID = %s" % TAG_ID[tagID])
                    else:
                        print("tagID        = %d" % tagID)
                    print("fieldType    = %s" % FIELD_TYPE[fieldType][0])
                    print("nValues      = %d" % nValues)
                    #if nValues == 1:
                    #    print("valueOffset =  %s" % valueOffset)
            return tagIDList, fieldTypeList, nValuesList, valueOffsetList

        def _readIFDEntry(self, tag, tagIDList, fieldTypeList, nValuesList, valueOffsetList):
            fd = self.fd
            st = self._structChar
            idx = tagIDList.index(tag)
            nValues = nValuesList[idx]
            output = []
            ftype, vfmt = FIELD_TYPE[fieldTypeList[idx]]
            vfmt = st + "%d%s" % (nValues, vfmt)
            requestedBytes = struct.calcsize(vfmt)
            if nValues == 1:
                output.append(valueOffsetList[idx])
            elif requestedBytes < 5:
                output.append(valueOffsetList[idx])
            else:
                offset = fd.seek(struct.unpack(st + "I", valueOffsetList[idx])[0])
                output = struct.unpack(vfmt, fd.read(requestedBytes))
            return output

        def getData(self, nImage, **kw):
            if nImage >= len(self._IFD):
                #update prior to raise an index error error
                self._updateIFD()
            return self._readImage(nImage, **kw)

        def getImage(self, nImage):
            return self.getData(nImage)

        def getInfo(self, nImage, **kw):
            if nImage >= len(self._IFD):
                #update prior to raise an index error error
                self._updateIFD()
            current = self._IFD[nImage]
            return self._readInfo(nImage)

        def _readInfo(self, nImage, close=True):
            if nImage in self._imageInfoCacheIndex:
                if DEBUG:
                    print("Reading info from cache")
                return self._imageInfoCache[self._imageInfoCacheIndex.index(nImage)]

            #read the header
            self.__makeSureFileIsOpen()
            tagIDList, fieldTypeList, nValuesList, valueOffsetList = self._parseImageFileDirectory(nImage)

            #rows and columns
            nColumns = valueOffsetList[tagIDList.index(TAG_NUMBER_OF_COLUMNS)]
            nRows = valueOffsetList[tagIDList.index(TAG_NUMBER_OF_ROWS)]

            #bits per sample
            idx = tagIDList.index(TAG_BITS_PER_SAMPLE)
            nBits = valueOffsetList[idx]
            if nValuesList[idx] != 1:
                #this happens with RGB and friends, nBits is not a single value
                nBits = self._readIFDEntry(TAG_BITS_PER_SAMPLE,
                                              tagIDList, fieldTypeList, nValuesList, valueOffsetList)

            if TAG_COLORMAP in tagIDList:
                idx = tagIDList.index(TAG_COLORMAP)
                tmpColormap = self._readIFDEntry(TAG_COLORMAP,
                                              tagIDList, fieldTypeList, nValuesList, valueOffsetList)
                if max(tmpColormap) > 255:
                    tmpColormap = numpy.array(tmpColormap, dtype=numpy.uint16)
                    tmpColormap = (tmpColormap / 256.).astype(numpy.uint8)
                else:
                    tmpColormap = numpy.array(tmpColormap, dtype=numpy.uint8)
                tmpColormap.shape = 3, -1
                colormap = numpy.zeros((tmpColormap.shape[-1], 3), tmpColormap.dtype)
                colormap[:, :] = tmpColormap.T
                tmpColormap = None
            else:
                colormap = None

            #sample format
            if TAG_SAMPLE_FORMAT in tagIDList:
                sampleFormat = valueOffsetList[tagIDList.index(TAG_SAMPLE_FORMAT)]
            else:
                #set to unknown
                sampleFormat = SAMPLE_FORMAT_VOID

            # compression
            compression = False
            compression_type = 1
            if TAG_COMPRESSION in tagIDList:
                compression_type = valueOffsetList[tagIDList.index(TAG_COMPRESSION)]
                if compression_type == 1:
                    compression = False
                else:
                    compression = True

            #photometric interpretation
            interpretation = 1
            if TAG_PHOTOMETRIC_INTERPRETATION in tagIDList:
                interpretation = valueOffsetList[tagIDList.index(TAG_PHOTOMETRIC_INTERPRETATION)]
            else:
                print("WARNING: Non standard TIFF. Photometric interpretation TAG missing")
            helpString = ""
            if sys.version > '2.6':
                helpString = eval('b""')

            if TAG_IMAGE_DESCRIPTION in tagIDList:
                imageDescription = self._readIFDEntry(TAG_IMAGE_DESCRIPTION,
                        tagIDList, fieldTypeList, nValuesList, valueOffsetList)
                if type(imageDescription) in [type([1]), type((1,))]:
                    imageDescription = helpString.join(imageDescription)
            else:
                imageDescription = "%d/%d" % (nImage + 1, len(self._IFD))

            if sys.version < '3.0':
                defaultSoftware = "Unknown Software"
            else:
                defaultSoftware = bytes("Unknown Software",
                                        encoding='utf-8')
            if TAG_SOFTWARE in tagIDList:
                software = self._readIFDEntry(TAG_SOFTWARE,
                        tagIDList, fieldTypeList, nValuesList, valueOffsetList)
                if type(software) in [type([1]), type((1,))]:
                    software = helpString.join(software)
            else:
                software = defaultSoftware

            if software == defaultSoftware:
                try:
                    if sys.version < '3.0':
                        if imageDescription.upper().startswith("IMAGEJ"):
                            software = imageDescription.split("=")[0]
                    else:
                        tmpString = imageDescription.decode()
                        if tmpString.upper().startswith("IMAGEJ"):
                            software = bytes(tmpString.split("=")[0],
                                             encoding='utf-8')
                except:
                    pass

            if TAG_DATE in tagIDList:
                date = self._readIFDEntry(TAG_DATE,
                        tagIDList, fieldTypeList, nValuesList, valueOffsetList)
                if type(date) in [type([1]), type((1,))]:
                    date = helpString.join(date)
            else:
                date = "Unknown Date"

            stripOffsets = self._readIFDEntry(TAG_STRIP_OFFSETS,
                            tagIDList, fieldTypeList, nValuesList, valueOffsetList)
            if TAG_ROWS_PER_STRIP in tagIDList:
                rowsPerStrip = self._readIFDEntry(TAG_ROWS_PER_STRIP,
                            tagIDList, fieldTypeList, nValuesList, valueOffsetList)[0]
            else:
                rowsPerStrip = nRows
                print("WARNING: Non standard TIFF. Rows per strip TAG missing")

            if TAG_STRIP_BYTE_COUNTS in tagIDList:
                stripByteCounts = self._readIFDEntry(TAG_STRIP_BYTE_COUNTS,
                            tagIDList, fieldTypeList, nValuesList, valueOffsetList)
            else:
                print("WARNING: Non standard TIFF. Strip byte counts TAG missing")
                if hasattr(nBits, 'index'):
                    expectedSum = 0
                    for n in nBits:
                        expectedSum += int(nRows * nColumns * n / 8)
                else:
                    expectedSum = int(nRows * nColumns * nBits / 8)
                stripByteCounts = [expectedSum]

            if close:
                self.__makeSureFileIsClosed()

            if self._forceMonoOutput and (interpretation > 1):
                #color image but asked monochrome output
                nBits = 32
                colormap = None
                sampleFormat = SAMPLE_FORMAT_FLOAT
                interpretation = 1
                #we cannot rely on any cache in this case
                useInfoCache = False
                if DEBUG:
                    print("FORCED MONO")
            else:
                useInfoCache = True

            info = {}
            info["nRows"] = nRows
            info["nColumns"] = nColumns
            info["nBits"] = nBits
            info["compression"] = compression
            info["compression_type"] = compression_type
            info["imageDescription"] = imageDescription
            info["stripOffsets"] = stripOffsets #This contains the file offsets to the data positions
            info["rowsPerStrip"] = rowsPerStrip
            info["stripByteCounts"] = stripByteCounts #bytes in strip since I do not support compression
            info["software"] = software
            info["date"] = date
            info["colormap"] = colormap
            info["sampleFormat"] = sampleFormat
            info["photometricInterpretation"] = interpretation
            infoDict = {}
            if sys.version < '3.0':
                testString = 'PyMca'
            else:
                testString = eval('b"PyMca"')
            if software.startswith(testString):
                #str to make sure python 2.x sees it as string and not unicode
                if sys.version < '3.0':
                    descriptionString = imageDescription
                else:
                    descriptionString = str(imageDescription.decode())
                #interpret the image description in terms of supplied
                #information at writing time
                items = descriptionString.split('=')
                for i in range(int(len(items) / 2)):
                    key = "%s" % items[i * 2]
                    #get rid of the \n at the end of the value
                    value = "%s" % items[i * 2 + 1][:-1]
                    infoDict[key] = value
            info['info'] = infoDict

            if (self._maxImageCacheLength > 0) and useInfoCache:
                self._imageInfoCacheIndex.insert(0, nImage)
                self._imageInfoCache.insert(0, info)
                if len(self._imageInfoCacheIndex) > self._maxImageCacheLength:
                    self._imageInfoCacheIndex = self._imageInfoCacheIndex[:self._maxImageCacheLength]
                    self._imageInfoCache = self._imageInfoCache[:self._maxImageCacheLength]
            return info

        def _readImage(self, nImage, **kw):
            if DEBUG:
                print("Reading image %d" % nImage)
            if 'close' in kw:
                close = kw['close']
            else:
                close = True
            rowMin = kw.get('rowMin', None)
            rowMax = kw.get('rowMax', None)
            if nImage in self._imageDataCacheIndex:
                if DEBUG:
                    print("Reading image data from cache")
                return self._imageDataCache[self._imageDataCacheIndex.index(nImage)]

            self.__makeSureFileIsOpen()
            if self._forceMonoOutput:
                oldMono = True
            else:
                oldMono = False
            try:
                self._forceMonoOutput = False
                info = self._readInfo(nImage, close=False)
                self._forceMonoOutput = oldMono
            except:
                self._forceMonoOutput = oldMono
                raise
            compression = info['compression']
            compression_type = info['compression_type']
            if compression:
                if compression_type != 32773:
                    raise IOError("Compressed TIFF images not supported except packbits")
                else:
                    #PackBits compression
                    if DEBUG:
                        print("Using PackBits compression")

            interpretation = info["photometricInterpretation"]
            if interpretation == 2:
                #RGB
                pass
                #raise IOError("RGB Image. Only grayscale images supported")
            elif interpretation == 3:
                #Palette Color Image
                pass
                #raise IOError("Palette-color Image. Only grayscale images supported")
            elif interpretation > 2:
                #Palette Color Image
                raise IOError("Only grayscale images supported")

            nRows = info["nRows"]
            nColumns = info["nColumns"]
            nBits = info["nBits"]
            colormap = info["colormap"]
            sampleFormat = info["sampleFormat"]

            if rowMin is None:
                rowMin = 0

            if rowMax is None:
                rowMax = nRows - 1

            if rowMin < 0:
                rowMin = nRows - rowMin

            if rowMax < 0:
                rowMax = nRows - rowMax

            if rowMax < rowMin:
                txt = "Max Row smaller than Min Row. Reverse selection not supported"
                raise NotImplemented(txt)

            if rowMin >= nRows:
                raise IndexError("Image only has %d rows" % nRows)

            if rowMax >= nRows:
                raise IndexError("Image only has %d rows" % nRows)

            if sampleFormat == SAMPLE_FORMAT_FLOAT:
                if nBits == 32:
                    dtype = numpy.float32
                elif nBits == 64:
                    dtype = numpy.float64
                else:
                    raise ValueError("Unsupported number of bits for a float: %d" % nBits)
            elif sampleFormat in [SAMPLE_FORMAT_UINT, SAMPLE_FORMAT_VOID]:
                if nBits in [8, (8, 8, 8), [8, 8, 8]]:
                    dtype = numpy.uint8
                elif nBits in [16, (16, 16, 16), [16, 16, 16]]:
                    dtype = numpy.uint16
                elif nBits in [32, (32, 32, 32), [32, 32, 32]]:
                    dtype = numpy.uint32
                elif nBits in [64, (64, 64, 64), [64, 64, 64]]:
                    dtype = numpy.uint64
                else:
                    raise ValueError("Unsupported number of bits for unsigned int: %s" % (nBits,))
            elif sampleFormat == SAMPLE_FORMAT_INT:
                if nBits in [8, (8, 8, 8), [8, 8, 8]]:
                    dtype = numpy.int8
                elif nBits in [16, (16, 16, 16), [16, 16, 16]]:
                    dtype = numpy.int16
                elif nBits in [32, (32, 32, 32), [32, 32, 32]]:
                    dtype = numpy.int32
                elif nBits in [64, (64, 64, 64), [64, 64, 64]]:
                    dtype = numpy.int64
                else:
                    raise ValueError("Unsupported number of bits for signed int: %s" % (nBits,))
            else:
                raise ValueError("Unsupported combination. Bits = %s  Format = %d" % (nBits, sampleFormat))
            if hasattr(nBits, 'index'):
                image = numpy.zeros((nRows, nColumns, len(nBits)), dtype=dtype)
            elif colormap is not None:
                #should I use colormap dtype?
                image = numpy.zeros((nRows, nColumns, 3), dtype=dtype)
            else:
                image = numpy.zeros((nRows, nColumns), dtype=dtype)

            fd = self.fd
            st = self._structChar
            stripOffsets = info["stripOffsets"] #This contains the file offsets to the data positions
            rowsPerStrip = info["rowsPerStrip"]
            stripByteCounts = info["stripByteCounts"] #bytes in strip since I do not support compression

            rowStart = 0
            if len(stripOffsets) == 1:
                bytesPerRow = int(stripByteCounts[0] / rowsPerStrip)
                fd.seek(stripOffsets[0] + rowMin * bytesPerRow)
                nBytes = (rowMax - rowMin + 1) * bytesPerRow
                if self._swap:
                    readout = numpy.fromstring(fd.read(nBytes), dtype).byteswap()
                else:
                    readout = numpy.fromstring(fd.read(nBytes), dtype)
                if hasattr(nBits, 'index'):
                    readout.shape = -1, nColumns, len(nBits)
                elif info['colormap'] is not None:
                    readout = colormap[readout]
                else:
                    readout.shape = -1, nColumns
                image[rowMin:rowMax + 1, :] = readout
            else:
                for i in range(len(stripOffsets)):
                    #the amount of rows
                    nRowsToRead = rowsPerStrip
                    rowEnd = int(min(rowStart + nRowsToRead, nRows))
                    if rowEnd < rowMin:
                        rowStart += nRowsToRead
                        continue
                    if (rowStart > rowMax):
                        break
                    #we are in position
                    fd.seek(stripOffsets[i])
                    #the amount of bytes to read
                    nBytes = stripByteCounts[i]
                    if compression_type == 32773:
                        try:
                            bufferBytes = bytes()
                        except:
                            #python 2.5 ...
                            bufferBytes = ""
                        #packBits
                        readBytes = 0
                        #intermediate buffer
                        tmpBuffer = fd.read(nBytes)
                        while readBytes < nBytes:
                            n = struct.unpack('b', tmpBuffer[readBytes:(readBytes + 1)])[0]
                            readBytes += 1
                            if n >= 0:
                                #should I prevent reading more than the
                                #length of the chain? Let's python raise
                                #the exception...
                                bufferBytes += tmpBuffer[readBytes:\
                                                          readBytes + (n + 1)]
                                readBytes += (n + 1)
                            elif n > -128:
                                bufferBytes += (-n + 1) * tmpBuffer[readBytes:(readBytes + 1)]
                                readBytes += 1
                            else:
                                #if read -128 ignore the byte
                                continue
                        if self._swap:
                            readout = numpy.fromstring(bufferBytes, dtype).byteswap()
                        else:
                            readout = numpy.fromstring(bufferBytes, dtype)
                        if hasattr(nBits, 'index'):
                            readout.shape = -1, nColumns, len(nBits)
                        elif info['colormap'] is not None:
                            readout = colormap[readout]
                            readout.shape = -1, nColumns, 3
                        else:
                            readout.shape = -1, nColumns
                        image[rowStart:rowEnd, :] = readout
                    else:
                        if 1:
                            #use numpy
                            if self._swap:
                                readout = numpy.fromstring(fd.read(nBytes), dtype).byteswap()
                            else:
                                readout = numpy.fromstring(fd.read(nBytes), dtype)
                            if hasattr(nBits, 'index'):
                                readout.shape = -1, nColumns, len(nBits)
                            elif colormap is not None:
                                readout = colormap[readout]
                                readout.shape = -1, nColumns, 3
                            else:
                                readout.shape = -1, nColumns
                            image[rowStart:rowEnd, :] = readout
                        else:
                            #using struct
                            readout = numpy.array(struct.unpack(st + "%df" % int(nBytes / 4), fd.read(nBytes)),
                                                  dtype=dtype)
                            if hasattr(nBits, 'index'):
                                readout.shape = -1, nColumns, len(nBits)
                            elif colormap is not None:
                                readout = colormap[readout]
                                readout.shape = -1, nColumns, 3
                            else:
                                readout.shape = -1, nColumns
                            image[rowStart:rowEnd, :] = readout
                    rowStart += nRowsToRead
            if close:
                self.__makeSureFileIsClosed()

            if len(image.shape) == 3:
                #color image
                if self._forceMonoOutput:
                    #color image, convert to monochrome
                    image = (image[:, :, 0] * 0.114 + \
                             image[:, :, 1] * 0.587 + \
                             image[:, :, 2] * 0.299).astype(numpy.float32)

            if (rowMin == 0) and (rowMax == (nRows - 1)):
                self._imageDataCacheIndex.insert(0, nImage)
                self._imageDataCache.insert(0, image)
                if len(self._imageDataCacheIndex) > self._maxImageCacheLength:
                    self._imageDataCacheIndex = self._imageDataCacheIndex[:self._maxImageCacheLength]
                    self._imageDataCache = self._imageDataCache[:self._maxImageCacheLength]

            return image

        def writeImage(self, image0, info=None, software=None, date=None):
            if software is None:
                software = 'PyMca.TiffIO'
            #if date is None:
            #    date = time.ctime()

            self.__makeSureFileIsOpen()
            fd = self.fd
            #prior to do anything, perform some tests
            if not len(image0.shape):
                raise ValueError("Empty image")
            if len(image0.shape) == 1:
                #get a different view
                image = image0[:]
                image.shape = 1, -1
            else:
                image = image0

            if image.dtype == numpy.float64:
                image = image.astype(numpy.float32)
            fd.seek(0)
            mode = fd.mode
            name = fd.name
            if 'w' in mode:
                #we have to overwrite the file
                self.__makeSureFileIsClosed()
                fd = None
                if os.path.exists(name):
                    os.remove(name)
                fd = open(name, mode='wb+')
                self._initEmptyFile(fd)
            self.fd = fd

            #read the file size
            self.__makeSureFileIsOpen()
            fd = self.fd
            fd.seek(0, os.SEEK_END)
            endOfFile = fd.tell()
            if fd.tell() == 0:
                self._initEmptyFile(fd)
                fd.seek(0, os.SEEK_END)
                endOfFile = fd.tell()

            #init internal variables
            self._initInternalVariables(fd)
            st = self._structChar

            #get the image file directories
            nImages = self.getImageFileDirectories()
            if DEBUG:
                print("File contains %d images" % nImages)
            if nImages == 0:
                fd.seek(4)
                fmt = st + 'I'
                fd.write(struct.pack(fmt, endOfFile))
            else:
                fd.seek(self._IFD[-1])
                fmt = st + 'H'
                numberOfDirectoryEntries = struct.unpack(fmt, fd.read(struct.calcsize(fmt)))[0]
                fmt = st + 'I'
                pos = self._IFD[-1] + 2 + 12 * numberOfDirectoryEntries
                fd.seek(pos)
                fmt = st + 'I'
                fd.write(struct.pack(fmt, endOfFile))
            fd.flush()

            #and we can write at the end of the file, find out the file length
            fd.seek(0, os.SEEK_END)

            #get the description information from the input information
            if info is None:
                description = info
            else:
                description = "%s" % ""
                for key in info.keys():
                    description += "%s=%s\n" % (key, info[key])

            #get the image file directory
            outputIFD = self._getOutputIFD(image, description=description,
                                                  software=software,
                                                  date=date)

            #write the new IFD
            fd.write(outputIFD)

            #write the image
            if self._swap:
                fd.write(image.byteswap().tostring())
            else:
                fd.write(image.tostring())

            fd.flush()
            self.fd = fd
            self.__makeSureFileIsClosed()

        def _initEmptyFile(self, fd=None):
            if fd is None:
                fd = self.fd
            if sys.byteorder == "little":
                order = "II"
                #intel, little endian
                fileOrder = "little"
                self._structChar = '<'
            else:
                order = "MM"
                #motorola, high endian
                fileOrder = "big"
                self._structChar = '>'
            st = self._structChar
            if fileOrder == sys.byteorder:
                self._swap = False
            else:
                self._swap = True
            fd.seek(0)
            if sys.version < '3.0':
                fd.write(struct.pack(st + '2s', order))
                fd.write(struct.pack(st + 'H', 42))
                fd.write(struct.pack(st + 'I', 0))
            else:
                fd.write(struct.pack(st + '2s', bytes(order, 'utf-8')))
                fd.write(struct.pack(st + 'H', 42))
                fd.write(struct.pack(st + 'I', 0))
            fd.flush()

        def _getOutputIFD(self, image, description=None, software=None, date=None):
            #the tags have to be in order
            #the very minimum is
            #256:"NumberOfColumns",           # S or L ImageWidth
            #257:"NumberOfRows",              # S or L ImageHeight
            #258:"BitsPerSample",             # S Number of bits per component
            #259:"Compression",               # SHORT (1 - NoCompression, ...
            #262:"PhotometricInterpretation", # SHORT (0 - WhiteIsZero, 1 -BlackIsZero, 2 - RGB, 3 - Palette color
            #270:"ImageDescription",          # ASCII
            #273:"StripOffsets",              # S or L, for each strip, the byte offset of the strip
            #278:"RowsPerStrip",              # S or L, number of rows in each back may be not for the last
            #279:"StripByteCounts",           # S or L, The number of bytes in the strip AFTER any compression
            #305:"Software",                  # ASCII
            #306:"Date",                      # ASCII
            #339:"SampleFormat",              # SHORT Interpretation of data in each pixel

            nDirectoryEntries = 9
            imageDescription = None
            if description is not None:
                descriptionLength = len(description)
                while descriptionLength < 4:
                    description = description + " "
                    descriptionLength = len(description)
                if sys.version >= '3.0':
                    description = bytes(description, 'utf-8')
                elif type(description) != type(""):
                    try:
                        description = description.decode('utf-8')
                    except UnicodeDecodeError:
                        try:
                            description = description.decode('latin-1')
                        except UnicodeDecodeError:
                            description = "%s" % description
                    if sys.version > '2.6':
                        description = description.encode('utf-8', errors="ignore")
                    description = "%s" % description
                descriptionLength = len(description)
                imageDescription = struct.pack("%ds" % descriptionLength, description)
                nDirectoryEntries += 1

            #software
            if software is not None:
                softwareLength = len(software)
                while softwareLength < 4:
                    software = software + " "
                    softwareLength = len(software)
                if sys.version >= '3.0':
                    software = bytes(software, 'utf-8')
                softwarePackedString = struct.pack("%ds" % softwareLength, software)
                nDirectoryEntries += 1
            else:
                softwareLength = 0

            if date is not None:
                dateLength = len(date)
                if sys.version >= '3.0':
                    date = bytes(date, 'utf-8')
                datePackedString = struct.pack("%ds" % dateLength, date)
                dateLength = len(datePackedString)
                nDirectoryEntries += 1
            else:
                dateLength = 0

            nRows, nColumns = image.shape
            dtype = image.dtype
            bitsPerSample = int(dtype.str[-1]) * 8

            #only uncompressed data
            compression = 1

            #interpretation, black is zero
            interpretation = 1

            #image description
            if imageDescription is not None:
                descriptionLength = len(imageDescription)
            else:
                descriptionLength = 0

            #strip offsets
            #we are putting them after the directory and the directory is
            #at the end of the file
            self.fd.seek(0, os.SEEK_END)
            endOfFile = self.fd.tell()
            if endOfFile == 0:
                #empty file
                endOfFile = 8

            #rows per strip
            if ALLOW_MULTIPLE_STRIPS:
                #try to segment the image in several pieces
                if not (nRows % 4):
                    rowsPerStrip = int(nRows / 4)
                elif not (nRows % 10):
                    rowsPerStrip = int(nRows / 10)
                elif not (nRows % 8):
                    rowsPerStrip = int(nRows / 8)
                elif not (nRows % 4):
                    rowsPerStrip = int(nRows / 4)
                elif not (nRows % 2):
                    rowsPerStrip = int(nRows / 2)
                else:
                    rowsPerStrip = nRows
            else:
                rowsPerStrip = nRows

            #stripByteCounts
            stripByteCounts = int(nColumns * rowsPerStrip * bitsPerSample / 8)

            if descriptionLength > 4:
                stripOffsets0 = endOfFile + dateLength + descriptionLength + \
                            2 + 12 * nDirectoryEntries + 4
            else:
                stripOffsets0 = endOfFile + dateLength + \
                            2 + 12 * nDirectoryEntries + 4

            if softwareLength > 4:
                stripOffsets0 += softwareLength

            stripOffsets = [stripOffsets0]
            stripOffsetsLength = 0
            stripOffsetsString = None

            st = self._structChar

            if rowsPerStrip != nRows:
                nStripOffsets = int(nRows / rowsPerStrip)
                fmt = st + 'I'
                stripOffsetsLength = struct.calcsize(fmt) * nStripOffsets
                stripOffsets0 += stripOffsetsLength
                #the length for the stripByteCounts will be the same
                stripOffsets0 += stripOffsetsLength
                stripOffsets = []
                for i in range(nStripOffsets):
                    value = stripOffsets0 + i * stripByteCounts
                    stripOffsets.append(value)
                    if i == 0:
                        stripOffsetsString = struct.pack(fmt, value)
                        stripByteCountsString = struct.pack(fmt, stripByteCounts)
                    else:
                        stripOffsetsString += struct.pack(fmt, value)
                        stripByteCountsString += struct.pack(fmt, stripByteCounts)

            if DEBUG:
                print("IMAGE WILL START AT %d" % stripOffsets[0])

            #sample format
            if dtype in [numpy.float32, numpy.float64] or\
               dtype.str[-2] == 'f':
                sampleFormat = SAMPLE_FORMAT_FLOAT
            elif dtype in [numpy.uint8, numpy.uint16, numpy.uint32, numpy.uint64]:
                sampleFormat = SAMPLE_FORMAT_UINT
            elif dtype in [numpy.int8, numpy.int16, numpy.int32, numpy.int64]:
                sampleFormat = SAMPLE_FORMAT_INT
            else:
                raise ValueError("Unsupported data type %s" % dtype)

            info = {}
            info["nColumns"] = nColumns
            info["nRows"] = nRows
            info["nBits"] = bitsPerSample
            info["compression"] = compression
            info["photometricInterpretation"] = interpretation
            info["stripOffsets"] = stripOffsets
            info["rowsPerStrip"] = rowsPerStrip
            info["stripByteCounts"] = stripByteCounts
            info["date"] = date
            info["sampleFormat"] = sampleFormat

            outputIFD = ""
            if sys.version > '2.6':
                outputIFD = eval('b""')

            fmt = st + "H"
            outputIFD += struct.pack(fmt, nDirectoryEntries)

            fmt = st + "HHII"
            outputIFD += struct.pack(fmt, TAG_NUMBER_OF_COLUMNS,
                                             FIELD_TYPE_OUT['I'],
                                             1,
                                             info["nColumns"])
            outputIFD += struct.pack(fmt, TAG_NUMBER_OF_ROWS,
                                             FIELD_TYPE_OUT['I'],
                                             1,
                                             info["nRows"])

            fmt = st + 'HHIHH'
            outputIFD += struct.pack(fmt, TAG_BITS_PER_SAMPLE,
                                             FIELD_TYPE_OUT['H'],
                                             1,
                                             info["nBits"], 0)
            fmt = st + 'HHIHH'
            outputIFD += struct.pack(fmt, TAG_COMPRESSION,
                                             FIELD_TYPE_OUT['H'],
                                             1,
                                             info["compression"], 0)
            fmt = st + 'HHIHH'
            outputIFD += struct.pack(fmt, TAG_PHOTOMETRIC_INTERPRETATION,
                                             FIELD_TYPE_OUT['H'],
                                             1,
                                             info["photometricInterpretation"], 0)

            if imageDescription is not None:
                descriptionLength = len(imageDescription)
                if descriptionLength > 4:
                    fmt = st + 'HHII'
                    outputIFD += struct.pack(fmt, TAG_IMAGE_DESCRIPTION,
                                             FIELD_TYPE_OUT['s'],
                                             descriptionLength,
                                             info["stripOffsets"][0] - \
                                             2 * stripOffsetsLength - \
                                             descriptionLength)
                else:
                    #it has to have length 4
                    fmt = st + 'HHI%ds' % descriptionLength
                    outputIFD += struct.pack(fmt, TAG_IMAGE_DESCRIPTION,
                                             FIELD_TYPE_OUT['s'],
                                             descriptionLength,
                                             description)

            if len(stripOffsets) == 1:
                fmt = st + 'HHII'
                outputIFD += struct.pack(fmt, TAG_STRIP_OFFSETS,
                                                 FIELD_TYPE_OUT['I'],
                                                 1,
                                                 info["stripOffsets"][0])
            else:
                fmt = st + 'HHII'
                outputIFD += struct.pack(fmt, TAG_STRIP_OFFSETS,
                                                 FIELD_TYPE_OUT['I'],
                                                 len(stripOffsets),
                        info["stripOffsets"][0] - 2 * stripOffsetsLength)

            fmt = st + 'HHII'
            outputIFD += struct.pack(fmt, TAG_ROWS_PER_STRIP,
                                             FIELD_TYPE_OUT['I'],
                                             1,
                                             info["rowsPerStrip"])

            if len(stripOffsets) == 1:
                fmt = st + 'HHII'
                outputIFD += struct.pack(fmt, TAG_STRIP_BYTE_COUNTS,
                                                 FIELD_TYPE_OUT['I'],
                                                 1,
                                                 info["stripByteCounts"])
            else:
                fmt = st + 'HHII'
                outputIFD += struct.pack(fmt, TAG_STRIP_BYTE_COUNTS,
                                                 FIELD_TYPE_OUT['I'],
                                                 len(stripOffsets),
                        info["stripOffsets"][0] - stripOffsetsLength)

            if software is not None:
                if softwareLength > 4:
                    fmt = st + 'HHII'
                    outputIFD += struct.pack(fmt, TAG_SOFTWARE,
                                             FIELD_TYPE_OUT['s'],
                                             softwareLength,
                                             info["stripOffsets"][0] - \
                                             2 * stripOffsetsLength - \
                                descriptionLength - softwareLength - dateLength)
                else:
                    #it has to have length 4
                    fmt = st + 'HHI%ds' % softwareLength
                    outputIFD += struct.pack(fmt, TAG_SOFTWARE,
                                             FIELD_TYPE_OUT['s'],
                                             softwareLength,
                                             softwarePackedString)

            if date is not None:
                fmt = st + 'HHII'
                outputIFD += struct.pack(fmt, TAG_DATE,
                                          FIELD_TYPE_OUT['s'],
                                          dateLength,
                                          info["stripOffsets"][0] - \
                                             2 * stripOffsetsLength - \
                                          descriptionLength - dateLength)

            fmt = st + 'HHIHH'
            outputIFD += struct.pack(fmt, TAG_SAMPLE_FORMAT,
                                             FIELD_TYPE_OUT['H'],
                                             1,
                                             info["sampleFormat"], 0)
            fmt = st + 'I'
            outputIFD += struct.pack(fmt, 0)

            if softwareLength > 4:
                outputIFD += softwarePackedString

            if date is not None:
                outputIFD += datePackedString

            if imageDescription is not None:
                if descriptionLength > 4:
                    outputIFD += imageDescription

            if stripOffsetsString is not None:
                outputIFD += stripOffsetsString
                outputIFD += stripByteCountsString

            return outputIFD

    if __name__ == "__main__":
        filename = sys.argv[1]
        dtype = numpy.uint16
        if not os.path.exists(filename):
            print("Testing file creation")
            tif = TiffIO(filename, mode='wb+')
            data = numpy.arange(10000).astype(dtype)
            data.shape = 100, 100
            tif.writeImage(data, info={'Title':'1st'})
            tif = None
            if os.path.exists(filename):
                print("Testing image appending")
                tif = TiffIO(filename, mode='rb+')
                tif.writeImage((data * 2).astype(dtype), info={'Title':'2nd'})
                tif = None
        tif = TiffIO(filename)
        print("Number of images = %d" % tif.getNumberOfImages())
        for i in range(tif.getNumberOfImages()):
            info = tif.getInfo(i)
            for key in info:
                if key not in ["colormap"]:
                    print("%s = %s" % (key, info[key]))
                elif info['colormap'] is not None:
                    print("RED   %s = %s" % (key, info[key][0:10, 0]))
                    print("GREEN %s = %s" % (key, info[key][0:10, 1]))
                    print("BLUE  %s = %s" % (key, info[key][0:10, 2]))
            data = tif.getImage(i)[0, 0:10]
            print("data [0, 0:10] = ", data)

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