# pydicom_PIL.py
"""View DICOM images using Python image Library (PIL)

Usage:
>>> import dicom
>>> from dicom.contrib.pydicom_PIL import show_PIL
>>> ds = dicom.read_file("filename")
>>> show_PIL(ds)

Requires Numpy:  http://numpy.scipy.org/
and Python Imaging Library:   http://www.pythonware.com/products/pil/

"""
# Copyright (c) 2009 Darcy Mason, Adit Panchal
# This file is part of pydicom, relased under an MIT license.
#    See the file license.txt included with this distribution, also
#    available at http://pydicom.googlecode.com

# Based on image.py from pydicom version 0.9.3,
#    LUT code added by Adit Panchal
# Tested on Python 2.5.4 (32-bit) on Mac OS X 10.6
#    using numpy 1.3.0 and PIL 1.1.7b1

have_PIL = True
try:
    import PIL.Image
except:
    have_PIL = False

have_numpy = True
try:
    import numpy as np
except:
    have_numpy = False


def get_LUT_value(data, window, level):
    """Apply the RGB Look-Up Table for the given data and window/level value."""
    if not have_numpy:
        raise ImportError("Numpy is not available. See http://numpy.scipy.org/ to download and install")

    return np.piecewise(data,
                        [data <= (level - 0.5 - (window - 1) / 2),
                         data > (level - 0.5 + (window - 1) / 2)],
                        [0, 255, lambda data: ((data - (level - 0.5)) / (window - 1) + 0.5) * (255 - 0)])


# Display an image using the Python Imaging Library (PIL)
def show_PIL(dataset):
    if not have_PIL:
        raise ImportError("Python Imaging Library is not available. See http://www.pythonware.com/products/pil/ to download and install")
    if ('PixelData' not in dataset):
        raise TypeError("Cannot show image -- DICOM dataset does not have pixel data")
    if ('WindowWidth' not in dataset) or ('WindowCenter' not in dataset):  # can only apply LUT if these values exist
        bits = dataset.BitsAllocated
        samples = dataset.SamplesPerPixel
        if bits == 8 and samples == 1:
            mode = "L"
        elif bits == 8 and samples == 3:
            mode = "RGB"
        elif bits == 16:
            mode = "I;16"  # not sure about this -- PIL source says is 'experimental' and no documentation. Also, should bytes swap depending on endian of file and system??
        else:
            raise TypeError("Don't know PIL mode for %d BitsAllocated and %d SamplesPerPixel" % (bits, samples))

        # PIL size = (width, height)
        size = (dataset.Columns, dataset.Rows)

        im = PIL.Image.frombuffer(mode, size, dataset.PixelData, "raw", mode, 0, 1)  # Recommended to specify all details by http://www.pythonware.com/library/pil/handbook/image.htm

    else:
        image = get_LUT_value(dataset.pixel_array, dataset.WindowWidth, dataset.WindowCenter)
        im = PIL.Image.fromarray(image).convert('L')  # Convert mode to L since LUT has only 256 values: http://www.pythonware.com/library/pil/handbook/image.htm

    im.show()