# $Id$
# a minimalist CCITT G3/G4 libtiff loader for PIL

# you need the 'ctypes' python extension, and the appropriate libtiff
# DLL files ('libtiff3.dll', 'jpeg62.dll', and 'zlib1.dll').  copies
# of the latter are included under ./DLLs.

# this loader has only been tested on a small number of CCITT G4 com-
# pressed bilevel (mode 1) samples, and definitely needs more work to
# handle more TIFF file flavours.

# TODO: add proper function signatures
# TODO: test with more modes and samples
# TODO: handle tiled images
# TODO: test on unix

import Image
import ctypes

import os, sys

if sys.platform == "win32":
    dllroot = os.path.join(os.path.dirname(__file__), "DLLs")
    if os.path.isdir(dllroot):
        os.environ["PATH"] = dllroot + os.pathsep + os.environ["PATH"]

libtiff = ctypes.cdll.libtiff3

##
# Loads a PIL image, using the libtiff library to read CCITT G3/G4
# files.
#
# @param im A PIL Image instance.

def libtiff_load(im):

    if im.format != "TIFF" or not im.tile:
        raise IOError("cannot load this image using libtiff")

    if im.tile[0][0] not in ("group3", "group4"):
        return im

    tif = libtiff.TIFFOpen(im.filename, "r")
    if not tif:
        raise IOError("libtiff failed to open the file")

    out = Image.new(im.mode, im.size, None)

    # allocate transfer buffer
    bufsize = libtiff.TIFFStripSize(tif)
    buf = ctypes.create_string_buffer(bufsize)

    # make sure that PIL and libtiff agrees on the layout
    if libtiff.TIFFNumberOfStrips(tif) != len(im.tile):
        raise IOError("wrong number of strips")

    # check polarity
    photometric_interpretation = im.tag.getscalar(262, 0)
    if photometric_interpretation:
        rawmode = "1" # min is black
    else:
        rawmode = "1;I" # min is white

    # copy strips to the PIL image
    for strip, tile in enumerate(im.tile):
        compression, bbox, offset, info = tile
        result = libtiff.TIFFReadEncodedStrip(tif, strip, buf, -1)
        if result < 0:
            raise IOError("libtiff failed to read strip")
        size = bbox[2]-bbox[0], bbox[3]-bbox[1]
        tile = Image.frombuffer(im.mode, size, buf, "raw", rawmode)
        out.paste(tile, bbox)

    libtiff.TIFFClose(tif)

    # update source image object
    im.tile = []
    im.im = out.im

    return im

# --------------------------------------------------------------------
# demo code

if __name__ == "__main__":

    import sys

    im = Image.open(sys.argv[1])
    print "mode", im.mode
    print "size", im.size
    print "tile", im.tile
    if im.format == "TIFF":
        libtiff_load(im)
    im.show()