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"""
A collection of image utilities using the Python Imaging Library (PIL).

Note that PIL is not a dependency of SciPy and this module is not
available on systems that don't have PIL installed.

"""
# Functions which need the PIL

import numpy
import tempfile

from numpy import amin, amax, ravel, asarray, cast, arange, \
     ones, newaxis, transpose, mgrid, iscomplexobj, sum, zeros, uint8, \
     issubdtype, array

try:
    from PIL import Image, ImageFilter
except ImportError:
    import Image
    import ImageFilter


__all__ = ['fromimage','toimage','imsave','imread','bytescale',
           'imrotate','imresize','imshow','imfilter','radon']


# Returns a byte-scaled image
def bytescale(data, cmin=None, cmax=None, high=255, low=0):
    """
Byte scales an array (image).

Byte scaling means converting the input image to uint8 dtype and scaling
the range to ``(low, high)`` (default 0-255).
If the input image already has dtype uint8, no scaling is done.

Parameters
----------
data : ndarray
PIL image data array.
cmin : scalar, optional
Bias scaling of small values. Default is ``data.min()``.
cmax : scalar, optional
Bias scaling of large values. Default is ``data.max()``.
high : scalar, optional
Scale max value to `high`. Default is 255.
low : scalar, optional
Scale min value to `low`. Default is 0.

Returns
-------
img_array : uint8 ndarray
The byte-scaled array.

Examples
--------
>>> img = array([[ 91.06794177, 3.39058326, 84.4221549 ],
[ 73.88003259, 80.91433048, 4.88878881],
[ 51.53875334, 34.45808177, 27.5873488 ]])
>>> bytescale(img)
array([[255, 0, 236],
[205, 225, 4],
[140, 90, 70]], dtype=uint8)
>>> bytescale(img, high=200, low=100)
array([[200, 100, 192],
[180, 188, 102],
[155, 135, 128]], dtype=uint8)
>>> bytescale(img, cmin=0, cmax=255)
array([[91, 3, 84],
[74, 81, 5],
[52, 34, 28]], dtype=uint8)

"""
    if data.dtype == uint8:
        return data

    if high < low:
        raise ValueError("`high` should be larger than `low`.")

    if cmin is None:
        cmin = data.min()
    if cmax is None:
        cmax = data.max()

    cscale = cmax - cmin
    if cscale < 0:
        raise ValueError("`cmax` should be larger than `cmin`.")
    elif cscale == 0:
        cscale = 1

    scale = float(high - low) / cscale
    bytedata = (data * 1.0 - cmin) * scale + 0.4999
    bytedata[bytedata > high] = high
    bytedata[bytedata < 0] = 0
    return cast[uint8](bytedata) + cast[uint8](low)

def imread(name,flatten=0):
    """
Read an image file from a filename.

Parameters
----------
name : str
The file name to be read.
flatten : bool, optional
If True, flattens the color layers into a single gray-scale layer.

Returns
-------
imread : ndarray
The array obtained by reading image from file `name`.

Notes
-----
The image is flattened by calling convert('F') on
the resulting image object.

"""

    im = Image.open(name)
    return fromimage(im,flatten=flatten)

def imsave(name, arr):
    """
Save an array as an image.

Parameters
----------
filename : str
Output filename.
image : ndarray, MxN or MxNx3 or MxNx4
Array containing image values. If the shape is ``MxN``, the array
represents a grey-level image. Shape ``MxNx3`` stores the red, green
and blue bands along the last dimension. An alpha layer may be
included, specified as the last colour band of an ``MxNx4`` array.

Examples
--------
Construct an array of gradient intensity values and save to file:

>>> x = np.zeros((255, 255))
>>> x = np.zeros((255, 255), dtype=np.uint8)
>>> x[:] = np.arange(255)
>>> imsave('/tmp/gradient.png', x)

Construct an array with three colour bands (R, G, B) and store to file:

>>> rgb = np.zeros((255, 255, 3), dtype=np.uint8)
>>> rgb[..., 0] = np.arange(255)
>>> rgb[..., 1] = 55
>>> rgb[..., 2] = 1 - np.arange(255)
>>> imsave('/tmp/rgb_gradient.png', rgb)

"""
    im = toimage(arr)
    im.save(name)
    return

def fromimage(im, flatten=0):
    """
Return a copy of a PIL image as a numpy array.

Parameters
----------
im : PIL image
Input image.
flatten : bool
If true, convert the output to grey-scale.

Returns
-------
fromimage : ndarray
The different colour bands/channels are stored in the
third dimension, such that a grey-image is MxN, an
RGB-image MxNx3 and an RGBA-image MxNx4.

"""
    if not Image.isImageType(im):
        raise TypeError("Input is not a PIL image.")
    if flatten:
        im = im.convert('F')
    elif im.mode == '1':
        # workaround for crash in PIL, see #1613.
        im.convert('L')

    return array(im)

_errstr = "Mode is unknown or incompatible with input array shape."

def toimage(arr, high=255, low=0, cmin=None, cmax=None, pal=None,
            mode=None, channel_axis=None):
    """Takes a numpy array and returns a PIL image.

The mode of the PIL image depends on the array shape and the `pal` and
`mode` keywords.

For 2-D arrays, if `pal` is a valid (N,3) byte-array giving the RGB values
(from 0 to 255) then ``mode='P'``, otherwise ``mode='L'``, unless mode
is given as 'F' or 'I' in which case a float and/or integer array is made.

Notes
-----
For 3-D arrays, the `channel_axis` argument tells which dimension of the
array holds the channel data.

For 3-D arrays if one of the dimensions is 3, the mode is 'RGB'
by default or 'YCbCr' if selected.

The numpy array must be either 2 dimensional or 3 dimensional.

"""
    data = asarray(arr)
    if iscomplexobj(data):
        raise ValueError("Cannot convert a complex-valued array.")
    shape = list(data.shape)
    valid = len(shape)==2 or ((len(shape)==3) and \
                              ((3 in shape) or (4 in shape)))
    if not valid:
        raise ValueError("'arr' does not have a suitable array shape for any mode.")
    if len(shape) == 2:
        shape = (shape[1],shape[0]) # columns show up first
        if mode == 'F':
            data32 = data.astype(numpy.float32)
            image = Image.fromstring(mode,shape,data32.tostring())
            return image
        if mode in [None, 'L', 'P']:
            bytedata = bytescale(data,high=high,low=low,cmin=cmin,cmax=cmax)
            image = Image.fromstring('L',shape,bytedata.tostring())
            if pal is not None:
                image.putpalette(asarray(pal,dtype=uint8).tostring())
                # Becomes a mode='P' automagically.
            elif mode == 'P': # default gray-scale
                pal = arange(0,256,1,dtype=uint8)[:,newaxis] * \
                      ones((3,),dtype=uint8)[newaxis,:]
                image.putpalette(asarray(pal,dtype=uint8).tostring())
            return image
        if mode == '1': # high input gives threshold for 1
            bytedata = (data > high)
            image = Image.fromstring('1',shape,bytedata.tostring())
            return image
        if cmin is None:
            cmin = amin(ravel(data))
        if cmax is None:
            cmax = amax(ravel(data))
        data = (data*1.0 - cmin)*(high-low)/(cmax-cmin) + low
        if mode == 'I':
            data32 = data.astype(numpy.uint32)
            image = Image.fromstring(mode,shape,data32.tostring())
        else:
            raise ValueError(_errstr)
        return image

    # if here then 3-d array with a 3 or a 4 in the shape length.
    # Check for 3 in datacube shape --- 'RGB' or 'YCbCr'
    if channel_axis is None:
        if (3 in shape):
            ca = numpy.flatnonzero(asarray(shape) == 3)[0]
        else:
            ca = numpy.flatnonzero(asarray(shape) == 4)
            if len(ca):
                ca = ca[0]
            else:
                raise ValueError("Could not find channel dimension.")
    else:
        ca = channel_axis

    numch = shape[ca]
    if numch not in [3,4]:
        raise ValueError("Channel axis dimension is not valid.")

    bytedata = bytescale(data,high=high,low=low,cmin=cmin,cmax=cmax)
    if ca == 2:
        strdata = bytedata.tostring()
        shape = (shape[1],shape[0])
    elif ca == 1:
        strdata = transpose(bytedata,(0,2,1)).tostring()
        shape = (shape[2],shape[0])
    elif ca == 0:
        strdata = transpose(bytedata,(1,2,0)).tostring()
        shape = (shape[2],shape[1])
    if mode is None:
        if numch == 3: mode = 'RGB'
        else: mode = 'RGBA'


    if mode not in ['RGB','RGBA','YCbCr','CMYK']:
        raise ValueError(_errstr)

    if mode in ['RGB', 'YCbCr']:
        if numch != 3:
            raise ValueError("Invalid array shape for mode.")
    if mode in ['RGBA', 'CMYK']:
        if numch != 4:
            raise ValueError("Invalid array shape for mode.")

    # Here we know data and mode is correct
    image = Image.fromstring(mode, shape, strdata)
    return image

def imrotate(arr,angle,interp='bilinear'):
    """
Rotate an image counter-clockwise by angle degrees.

Parameters
----------
arr : nd_array
Input array of image to be rotated.
angle : float
The angle of rotation.
interp : str, optional
Interpolation


Returns
-------
imrotate : nd_array
The rotated array of image.

Notes
-----

Interpolation methods can be:
* 'nearest' : for nearest neighbor
* 'bilinear' : for bilinear
* 'cubic' : cubic
* 'bicubic' : for bicubic

"""
    arr = asarray(arr)
    func = {'nearest':0,'bilinear':2,'bicubic':3,'cubic':3}
    im = toimage(arr)
    im = im.rotate(angle,resample=func[interp])
    return fromimage(im)

def imshow(arr):
    """
Simple showing of an image through an external viewer.

Uses the image viewer specified by the environment variable
SCIPY_PIL_IMAGE_VIEWER, or if that is not defined then `see`,
to view a temporary file generated from array data.

Parameters
----------
arr : ndarray
Array of image data to show.

Returns
-------
None

Examples
--------
>>> a = np.tile(np.arange(255), (255,1))
>>> from scipy import misc
>>> misc.pilutil.imshow(a)

"""
    im = toimage(arr)
    fnum,fname = tempfile.mkstemp('.png')
    try:
        im.save(fname)
    except:
        raise RuntimeError("Error saving temporary image data.")

    import os
    os.close(fnum)

    cmd = os.environ.get('SCIPY_PIL_IMAGE_VIEWER','see')
    status = os.system("%s %s" % (cmd,fname))

    os.unlink(fname)
    if status != 0:
        raise RuntimeError('Could not execute image viewer.')

def imresize(arr, size, interp='bilinear', mode=None):
    """
Resize an image.

Parameters
----------
arr : nd_array
The array of image to be resized.

size : int, float or tuple
* int - Percentage of current size.
* float - Fraction of current size.
* tuple - Size of the output image.

interp : str
Interpolation to use for re-sizing ('nearest', 'bilinear', 'bicubic'
or 'cubic').

mode : str
The PIL image mode ('P', 'L', etc.).

Returns
-------
imresize : ndarray
The resized array of image.

"""
    im = toimage(arr, mode=mode)
    ts = type(size)
    if issubdtype(ts,int):
        size = size / 100.0
    elif issubdtype(type(size),float):
        size = (array(im.size)*size).astype(int)
    else:
        size = (size[1],size[0])
    func = {'nearest':0,'bilinear':2,'bicubic':3,'cubic':3}
    imnew = im.resize(size, resample=func[interp])
    return fromimage(imnew)


def imfilter(arr,ftype):
    """
Simple filtering of an image.

Parameters
----------
arr : ndarray
The array of Image in which the filter is to be applied.
ftype : str
The filter that has to be applied. Legal values are:
'blur', 'contour', 'detail', 'edge_enhance', 'edge_enhance_more',
'emboss', 'find_edges', 'smooth', 'smooth_more', 'sharpen'.

Returns
-------
imfilter : ndarray
The array with filter applied.

Raises
------
ValueError
*Unknown filter type.* . If the filter you are trying
to apply is unsupported.

"""
    _tdict = {'blur':ImageFilter.BLUR,
              'contour':ImageFilter.CONTOUR,
              'detail':ImageFilter.DETAIL,
              'edge_enhance':ImageFilter.EDGE_ENHANCE,
              'edge_enhance_more':ImageFilter.EDGE_ENHANCE_MORE,
              'emboss':ImageFilter.EMBOSS,
              'find_edges':ImageFilter.FIND_EDGES,
              'smooth':ImageFilter.SMOOTH,
              'smooth_more':ImageFilter.SMOOTH_MORE,
              'sharpen':ImageFilter.SHARPEN
              }

    im = toimage(arr)
    if ftype not in _tdict.keys():
        raise ValueError("Unknown filter type.")
    return fromimage(im.filter(_tdict[ftype]))


def radon(arr,theta=None):
    """`radon` is deprecated in scipy 0.11, and will be removed in 0.12

For this functionality, please use the "radon" function in scikits-image.

"""
    if theta is None:
        theta = mgrid[0:180]
    s = zeros((arr.shape[1],len(theta)), float)
    k = 0
    for th in theta:
        im = imrotate(arr,-th)
        s[:,k] = sum(im,axis=0)
        k += 1
    return s


radon = numpy.deprecate(radon)
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