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colors.py

00001 """
A class for converting color arguments to RGB or RGBA

This class instantiates a single instance colorConverter that is used
to convert matlab color strings to RGB.  RGB is a tuple of float RGB
values in the range 0-1.

Commands which take color arguments can use several formats to specify
the colors.  For the basic builtin colors, you can use a single letter

      b  : blue
      g  : green
      r  : red
      c  : cyan
      m  : magenta
      y  : yellow
      k  : black
      w  : white

Gray shades can be given as a string encoding a float in the 0-1
range, e.g.::

    color = '0.75'

For a greater range of colors, you have two options.  You can specify
the color using an html hex string, as in::

      color = '#eeefff'

or you can pass an *R* , *G* , *B* tuple, where each of *R* , *G* , *B*
are in the range [0,1].

Finally, legal html names for colors, like 'red', 'burlywood' and
'chartreuse' are supported.
"""
import re
import numpy as np
from numpy import ma
import matplotlib.cbook as cbook

cnames = {
    'aliceblue'            : '#F0F8FF',
    'antiquewhite'         : '#FAEBD7',
    'aqua'                 : '#00FFFF',
    'aquamarine'           : '#7FFFD4',
    'azure'                : '#F0FFFF',
    'beige'                : '#F5F5DC',
    'bisque'               : '#FFE4C4',
    'black'                : '#000000',
    'blanchedalmond'       : '#FFEBCD',
    'blue'                 : '#0000FF',
    'blueviolet'           : '#8A2BE2',
    'brown'                : '#A52A2A',
    'burlywood'            : '#DEB887',
    'cadetblue'            : '#5F9EA0',
    'chartreuse'           : '#7FFF00',
    'chocolate'            : '#D2691E',
    'coral'                : '#FF7F50',
    'cornflowerblue'       : '#6495ED',
    'cornsilk'             : '#FFF8DC',
    'crimson'              : '#DC143C',
    'cyan'                 : '#00FFFF',
    'darkblue'             : '#00008B',
    'darkcyan'             : '#008B8B',
    'darkgoldenrod'        : '#B8860B',
    'darkgray'             : '#A9A9A9',
    'darkgreen'            : '#006400',
    'darkkhaki'            : '#BDB76B',
    'darkmagenta'          : '#8B008B',
    'darkolivegreen'       : '#556B2F',
    'darkorange'           : '#FF8C00',
    'darkorchid'           : '#9932CC',
    'darkred'              : '#8B0000',
    'darksalmon'           : '#E9967A',
    'darkseagreen'         : '#8FBC8F',
    'darkslateblue'        : '#483D8B',
    'darkslategray'        : '#2F4F4F',
    'darkturquoise'        : '#00CED1',
    'darkviolet'           : '#9400D3',
    'deeppink'             : '#FF1493',
    'deepskyblue'          : '#00BFFF',
    'dimgray'              : '#696969',
    'dodgerblue'           : '#1E90FF',
    'firebrick'            : '#B22222',
    'floralwhite'          : '#FFFAF0',
    'forestgreen'          : '#228B22',
    'fuchsia'              : '#FF00FF',
    'gainsboro'            : '#DCDCDC',
    'ghostwhite'           : '#F8F8FF',
    'gold'                 : '#FFD700',
    'goldenrod'            : '#DAA520',
    'gray'                 : '#808080',
    'green'                : '#008000',
    'greenyellow'          : '#ADFF2F',
    'honeydew'             : '#F0FFF0',
    'hotpink'              : '#FF69B4',
    'indianred'            : '#CD5C5C',
    'indigo'               : '#4B0082',
    'ivory'                : '#FFFFF0',
    'khaki'                : '#F0E68C',
    'lavender'             : '#E6E6FA',
    'lavenderblush'        : '#FFF0F5',
    'lawngreen'            : '#7CFC00',
    'lemonchiffon'         : '#FFFACD',
    'lightblue'            : '#ADD8E6',
    'lightcoral'           : '#F08080',
    'lightcyan'            : '#E0FFFF',
    'lightgoldenrodyellow' : '#FAFAD2',
    'lightgreen'           : '#90EE90',
    'lightgrey'            : '#D3D3D3',
    'lightpink'            : '#FFB6C1',
    'lightsalmon'          : '#FFA07A',
    'lightseagreen'        : '#20B2AA',
    'lightskyblue'         : '#87CEFA',
    'lightslategray'       : '#778899',
    'lightsteelblue'       : '#B0C4DE',
    'lightyellow'          : '#FFFFE0',
    'lime'                 : '#00FF00',
    'limegreen'            : '#32CD32',
    'linen'                : '#FAF0E6',
    'magenta'              : '#FF00FF',
    'maroon'               : '#800000',
    'mediumaquamarine'     : '#66CDAA',
    'mediumblue'           : '#0000CD',
    'mediumorchid'         : '#BA55D3',
    'mediumpurple'         : '#9370DB',
    'mediumseagreen'       : '#3CB371',
    'mediumslateblue'      : '#7B68EE',
    'mediumspringgreen'    : '#00FA9A',
    'mediumturquoise'      : '#48D1CC',
    'mediumvioletred'      : '#C71585',
    'midnightblue'         : '#191970',
    'mintcream'            : '#F5FFFA',
    'mistyrose'            : '#FFE4E1',
    'moccasin'             : '#FFE4B5',
    'navajowhite'          : '#FFDEAD',
    'navy'                 : '#000080',
    'oldlace'              : '#FDF5E6',
    'olive'                : '#808000',
    'olivedrab'            : '#6B8E23',
    'orange'               : '#FFA500',
    'orangered'            : '#FF4500',
    'orchid'               : '#DA70D6',
    'palegoldenrod'        : '#EEE8AA',
    'palegreen'            : '#98FB98',
    'palevioletred'        : '#AFEEEE',
    'papayawhip'           : '#FFEFD5',
    'peachpuff'            : '#FFDAB9',
    'peru'                 : '#CD853F',
    'pink'                 : '#FFC0CB',
    'plum'                 : '#DDA0DD',
    'powderblue'           : '#B0E0E6',
    'purple'               : '#800080',
    'red'                  : '#FF0000',
    'rosybrown'            : '#BC8F8F',
    'royalblue'            : '#4169E1',
    'saddlebrown'          : '#8B4513',
    'salmon'               : '#FA8072',
    'sandybrown'           : '#FAA460',
    'seagreen'             : '#2E8B57',
    'seashell'             : '#FFF5EE',
    'sienna'               : '#A0522D',
    'silver'               : '#C0C0C0',
    'skyblue'              : '#87CEEB',
    'slateblue'            : '#6A5ACD',
    'slategray'            : '#708090',
    'snow'                 : '#FFFAFA',
    'springgreen'          : '#00FF7F',
    'steelblue'            : '#4682B4',
    'tan'                  : '#D2B48C',
    'teal'                 : '#008080',
    'thistle'              : '#D8BFD8',
    'tomato'               : '#FF6347',
    'turquoise'            : '#40E0D0',
    'violet'               : '#EE82EE',
    'wheat'                : '#F5DEB3',
    'white'                : '#FFFFFF',
    'whitesmoke'           : '#F5F5F5',
    'yellow'               : '#FFFF00',
    'yellowgreen'          : '#9ACD32',
    }


# add british equivs
for k, v in cnames.items():
    if k.find('gray')>=0:
        k = k.replace('gray', 'grey')
        cnames[k] = v

def is_color_like(c):
    try:
        colorConverter.to_rgb(c)
        return True
    except ValueError:
        return False


def rgb2hex(rgb):
    'Given a len 3 rgb tuple of 0-1 floats, return the hex string'
    return '#%02x%02x%02x' % tuple([round(val*255) for val in rgb])

hexColorPattern = re.compile("\A#[a-fA-F0-9]{6}\Z")

00204 def hex2color(s):
    """
    Take a hex string *s* and return the corresponding rgb 3-tuple
    Example: #efefef -> (0.93725, 0.93725, 0.93725)
    """
    if not isinstance(s, basestring):
        raise TypeError('hex2color requires a string argument')
    if hexColorPattern.match(s) is None:
        raise ValueError('invalid hex color string "%s"' % s)
    return tuple([int(n, 16)/255.0 for n in (s[1:3], s[3:5], s[5:7])])

class ColorConverter:
    colors = {
        'b' : (0.0, 0.0, 1.0),
        'g' : (0.0, 0.5, 0.0),
        'r' : (1.0, 0.0, 0.0),
        'c' : (0.0, 0.75, 0.75),
        'm' : (0.75, 0, 0.75),
        'y' : (0.75, 0.75, 0),
        'k' : (0.0, 0.0, 0.0),
        'w' : (1.0, 1.0, 1.0),
        }

    cache = {}
    def to_rgb(self, arg):
        """
        Returns an *RGB* tuple of three floats from 0-1.

        *arg* can be an *RGB* or *RGBA* sequence or a string in any of
        several forms:

            1) a letter from the set 'rgbcmykw'
            2) a hex color string, like '#00FFFF'
            3) a standard name, like 'aqua'
            4) a float, like '0.4', indicating gray on a 0-1 scale

        if *arg* is *RGBA*, the *A* will simply be discarded.
        """
        try: return self.cache[arg]
        except KeyError: pass
        except TypeError: # could be unhashable rgb seq
            arg = tuple(arg)
            try: return self.cache[arg]
            except KeyError: pass
            except TypeError:
                raise ValueError(
                      'to_rgb: arg "%s" is unhashable even inside a tuple'
                                    % (str(arg),))

        try:
            if cbook.is_string_like(arg):
                color = self.colors.get(arg, None)
                if color is None:
                    str1 = cnames.get(arg, arg)
                    if str1.startswith('#'):
                        color = hex2color(str1)
                    else:
                        fl = float(arg)
                        if fl < 0 or fl > 1:
                            raise ValueError(
                                   'gray (string) must be in range 0-1')
                        color = tuple([fl]*3)
            elif cbook.iterable(arg):
                if len(arg) > 4 or len(arg) < 3:
                    raise ValueError(
                           'sequence length is %d; must be 3 or 4'%len(arg))
                color = tuple(arg[:3])
                if [x for x in color if (float(x) < 0) or  (x > 1)]:
                    # This will raise TypeError if x is not a number.
                    raise ValueError('number in rbg sequence outside 0-1 range')
            else:
                raise ValueError('cannot convert argument to rgb sequence')

            self.cache[arg] = color

        except (KeyError, ValueError, TypeError), exc:
            raise ValueError('to_rgb: Invalid rgb arg "%s"\n%s' % (str(arg), exc))
            # Error messages could be improved by handling TypeError
            # separately; but this should be rare and not too hard
            # for the user to figure out as-is.
        return color

    def to_rgba(self, arg, alpha=None):
        """
        Returns an *RGBA* tuple of four floats from 0-1.

        For acceptable values of *arg*, see :meth:`to_rgb`.
        If *arg* is an *RGBA* sequence and *alpha* is not *None*,
        *alpha* will replace the original *A*.
        """
        try:
            if not cbook.is_string_like(arg) and cbook.iterable(arg):
                if len(arg) == 4:
                    if [x for x in arg if (float(x) < 0) or  (x > 1)]:
                        # This will raise TypeError if x is not a number.
                        raise ValueError('number in rbga sequence outside 0-1 range')
                    if alpha is None:
                        return tuple(arg)
                    if alpha < 0.0 or alpha > 1.0:
                        raise ValueError("alpha must be in range 0-1")
                    return arg[0], arg[1], arg[2], arg[3] * alpha
                r,g,b = arg[:3]
                if [x for x in (r,g,b) if (float(x) < 0) or  (x > 1)]:
                    raise ValueError('number in rbg sequence outside 0-1 range')
            else:
                r,g,b = self.to_rgb(arg)
            if alpha is None:
                alpha = 1.0
            return r,g,b,alpha
        except (TypeError, ValueError), exc:
            raise ValueError('to_rgba: Invalid rgba arg "%s"\n%s' % (str(arg), exc))

    def to_rgba_array(self, c, alpha=None):
        """
        Returns an Numpy array of *RGBA* tuples.

        Accepts a single mpl color spec or a sequence of specs.
        If the sequence is a list or array, the items are changed in place,
        but an array copy is still returned.

        Special case to handle "no color": if *c* is "none" (case-insensitive),
        then an empty array will be returned.  Same for an empty list.
        """
        try:
            if c.lower() == 'none':
                return np.zeros((0,4), dtype=np.float_)
        except AttributeError:
            pass
        if len(c) == 0:
            return np.zeros((0,4), dtype=np.float_)
        try:
            result = [self.to_rgba(c, alpha)]
        except ValueError:
            # If c is a list it must be maintained as the same list
            # with modified items so that items can be appended to
            # it. This is needed for examples/dynamic_collections.py.
            if not isinstance(c, (list, np.ndarray)): # specific; don't need duck-typing
                c = list(c)
            for i, cc in enumerate(c):
                c[i] = self.to_rgba(cc, alpha)  # change in place
            result = c
        return np.asarray(result, np.float_)

colorConverter = ColorConverter()

00349 def makeMappingArray(N, data):
    """Create an *N* -element 1-d lookup table

    *data* represented by a list of x,y0,y1 mapping correspondences.
    Each element in this list represents how a value between 0 and 1
    (inclusive) represented by x is mapped to a corresponding value
    between 0 and 1 (inclusive). The two values of y are to allow
    for discontinuous mapping functions (say as might be found in a
    sawtooth) where y0 represents the value of y for values of x
    <= to that given, and y1 is the value to be used for x > than
    that given). The list must start with x=0, end with x=1, and
    all values of x must be in increasing order. Values between
    the given mapping points are determined by simple linear interpolation.

    The function returns an array "result" where ``result[x*(N-1)]``
    gives the closest value for values of x between 0 and 1.
    """
    try:
        adata = np.array(data)
    except:
        raise TypeError("data must be convertable to an array")
    shape = adata.shape
    if len(shape) != 2 and shape[1] != 3:
        raise ValueError("data must be nx3 format")

    x  = adata[:,0]
    y0 = adata[:,1]
    y1 = adata[:,2]

    if x[0] != 0. or x[-1] != 1.0:
        raise ValueError(
           "data mapping points must start with x=0. and end with x=1")
    if np.sometrue(np.sort(x)-x):
        raise ValueError(
           "data mapping points must have x in increasing order")
    # begin generation of lookup table
    x = x * (N-1)
    lut = np.zeros((N,), np.float)
    xind = np.arange(float(N))
    ind = np.searchsorted(x, xind)[1:-1]

    lut[1:-1] = ( ((xind[1:-1] - x[ind-1]) / (x[ind] - x[ind-1]))
                  * (y0[ind] - y1[ind-1]) + y1[ind-1])
    lut[0] = y1[0]
    lut[-1] = y0[-1]
    # ensure that the lut is confined to values between 0 and 1 by clipping it
    np.clip(lut, 0.0, 1.0)
    #lut = where(lut > 1., 1., lut)
    #lut = where(lut < 0., 0., lut)
    return lut


00401 class Colormap:
    """Base class for all scalar to rgb mappings

        Important methods:

            * :meth:`set_bad`
            * :meth:`set_under`
            * :meth:`set_over`
    """
00410     def __init__(self, name, N=256):
        """
        Public class attributes:
            :attr:`N` : number of rgb quantization levels
            :attr:`name` : name of colormap

        """
        self.name = name
        self.N = N
        self._rgba_bad = (0.0, 0.0, 0.0, 0.0) # If bad, don't paint anything.
        self._rgba_under = None
        self._rgba_over = None
        self._i_under = N
        self._i_over = N+1
        self._i_bad = N+2
        self._isinit = False


00428     def __call__(self, X, alpha=1.0, bytes=False):
        """
        *X* is either a scalar or an array (of any dimension).
        If scalar, a tuple of rgba values is returned, otherwise
        an array with the new shape = oldshape+(4,). If the X-values
        are integers, then they are used as indices into the array.
        If they are floating point, then they must be in the
        interval (0.0, 1.0).
        Alpha must be a scalar.
        If bytes is False, the rgba values will be floats on a
        0-1 scale; if True, they will be uint8, 0-255.
        """

        if not self._isinit: self._init()
        alpha = min(alpha, 1.0) # alpha must be between 0 and 1
        alpha = max(alpha, 0.0)
        self._lut[:-3, -1] = alpha
        mask_bad = None
        if not cbook.iterable(X):
            vtype = 'scalar'
            xa = np.array([X])
        else:
            vtype = 'array'
            xma = ma.asarray(X)
            xa = xma.filled(0)
            mask_bad = ma.getmask(xma)
        if xa.dtype.char in np.typecodes['Float']:
            np.putmask(xa, xa==1.0, 0.9999999) #Treat 1.0 as slightly less than 1.
            xa = (xa * self.N).astype(int)
        # Set the over-range indices before the under-range;
        # otherwise the under-range values get converted to over-range.
        np.putmask(xa, xa>self.N-1, self._i_over)
        np.putmask(xa, xa<0, self._i_under)
        if mask_bad is not None and mask_bad.shape == xa.shape:
            np.putmask(xa, mask_bad, self._i_bad)
        if bytes:
            lut = (self._lut * 255).astype(np.uint8)
        else:
            lut = self._lut
        rgba = np.empty(shape=xa.shape+(4,), dtype=lut.dtype)
        lut.take(xa, axis=0, mode='clip', out=rgba)
                    #  twice as fast as lut[xa];
                    #  using the clip or wrap mode and providing an
                    #  output array speeds it up a little more.
        if vtype == 'scalar':
            rgba = tuple(rgba[0,:])
        return rgba

00476     def set_bad(self, color = 'k', alpha = 1.0):
        '''Set color to be used for masked values.
        '''
        self._rgba_bad = colorConverter.to_rgba(color, alpha)
        if self._isinit: self._set_extremes()

00482     def set_under(self, color = 'k', alpha = 1.0):
        '''Set color to be used for low out-of-range values.
           Requires norm.clip = False
        '''
        self._rgba_under = colorConverter.to_rgba(color, alpha)
        if self._isinit: self._set_extremes()

00489     def set_over(self, color = 'k', alpha = 1.0):
        '''Set color to be used for high out-of-range values.
           Requires norm.clip = False
        '''
        self._rgba_over = colorConverter.to_rgba(color, alpha)
        if self._isinit: self._set_extremes()

    def _set_extremes(self):
        if self._rgba_under:
            self._lut[self._i_under] = self._rgba_under
        else:
            self._lut[self._i_under] = self._lut[0]
        if self._rgba_over:
            self._lut[self._i_over] = self._rgba_over
        else:
            self._lut[self._i_over] = self._lut[self.N-1]
        self._lut[self._i_bad] = self._rgba_bad

00507     def _init():
        '''Generate the lookup table, self._lut'''
        raise NotImplementedError("Abstract class only")

    def is_gray(self):
        if not self._isinit: self._init()
        return (np.alltrue(self._lut[:,0] == self._lut[:,1])
                    and np.alltrue(self._lut[:,0] == self._lut[:,2]))


00517 class LinearSegmentedColormap(Colormap):
    """Colormap objects based on lookup tables using linear segments.

    The lookup transfer function is a simple linear function between
    defined intensities. There is no limit to the number of segments
    that may be defined. Though as the segment intervals start containing
    fewer and fewer array locations, there will be inevitable quantization
    errors
    """
00526     def __init__(self, name, segmentdata, N=256):
        """Create color map from linear mapping segments

        segmentdata argument is a dictionary with a red, green and blue
        entries. Each entry should be a list of x, y0, y1 tuples.
        See makeMappingArray for details
        """
        self.monochrome = False  # True only if all colors in map are identical;
                                 # needed for contouring.
        Colormap.__init__(self, name, N)
        self._segmentdata = segmentdata

    def _init(self):
        self._lut = np.ones((self.N + 3, 4), np.float)
        self._lut[:-3, 0] = makeMappingArray(self.N, self._segmentdata['red'])
        self._lut[:-3, 1] = makeMappingArray(self.N, self._segmentdata['green'])
        self._lut[:-3, 2] = makeMappingArray(self.N, self._segmentdata['blue'])
        self._isinit = True
        self._set_extremes()


00547 class ListedColormap(Colormap):
    """Colormap object generated from a list of colors.

    This may be most useful when indexing directly into a colormap,
    but it can also be used to generate special colormaps for ordinary
    mapping.
    """
00554     def __init__(self, colors, name = 'from_list', N = None):
        """
        Make a colormap from a list of colors.

        *colors*
            a list of matplotlib color specifications,
            or an equivalent Nx3 floating point array (*N* rgb values)
        *name*
            a string to identify the colormap
        *N*
            the number of entries in the map.  The default is *None*,
            in which case there is one colormap entry for each
            element in the list of colors.  If::

                N < len(colors)

            the list will be truncated at *N*.  If::

                N > len(colors)

            the list will be extended by repetition.
        """
        self.colors = colors
        self.monochrome = False  # True only if all colors in map are identical;
                                 # needed for contouring.
        if N is None:
            N = len(self.colors)
        else:
            if cbook.is_string_like(self.colors):
                self.colors = [self.colors] * N
                self.monochrome = True
            elif cbook.iterable(self.colors):
                self.colors = list(self.colors) # in case it was a tuple
                if len(self.colors) == 1:
                    self.monochrome = True
                if len(self.colors) < N:
                    self.colors = list(self.colors) * N
                del(self.colors[N:])
            else:
                try: gray = float(self.colors)
                except TypeError: pass
                else:  self.colors = [gray] * N
                self.monochrome = True
        Colormap.__init__(self, name, N)


    def _init(self):
        rgb = np.array([colorConverter.to_rgb(c)
                    for c in self.colors], np.float)
        self._lut = np.zeros((self.N + 3, 4), np.float)
        self._lut[:-3, :-1] = rgb
        self._lut[:-3, -1] = 1
        self._isinit = True
        self._set_extremes()


00610 class Normalize:
    """
    Normalize a given value to the 0-1 range
    """
00614     def __init__(self, vmin=None, vmax=None, clip=False):
        """
        If *vmin* or *vmax* is not given, they are taken from the input's
        minimum and maximum value respectively.  If *clip* is *True* and
        the given value falls outside the range, the returned value
        will be 0 or 1, whichever is closer. Returns 0 if::

            vmin==vmax

        Works with scalars or arrays, including masked arrays.  If
        *clip* is *True*, masked values are set to 1; otherwise they
        remain masked.  Clipping silently defeats the purpose of setting
        the over, under, and masked colors in the colormap, so it is
        likely to lead to surprises; therefore the default is
        *clip* = *False*.
        """
        self.vmin = vmin
        self.vmax = vmax
        self.clip = clip

    def __call__(self, value, clip=None):
        if clip is None:
            clip = self.clip

        if cbook.iterable(value):
            vtype = 'array'
            val = ma.asarray(value).astype(np.float)
        else:
            vtype = 'scalar'
            val = ma.array([value]).astype(np.float)

        self.autoscale_None(val)
        vmin, vmax = self.vmin, self.vmax
        if vmin > vmax:
            raise ValueError("minvalue must be less than or equal to maxvalue")
        elif vmin==vmax:
            return 0.0 * val
        else:
            if clip:
                mask = ma.getmask(val)
                val = ma.array(np.clip(val.filled(vmax), vmin, vmax),
                                mask=mask)
            result = (val-vmin) * (1.0/(vmax-vmin))
        if vtype == 'scalar':
            result = result[0]
        return result

    def inverse(self, value):
        if not self.scaled():
            raise ValueError("Not invertible until scaled")
        vmin, vmax = self.vmin, self.vmax

        if cbook.iterable(value):
            val = ma.asarray(value)
            return vmin + val * (vmax - vmin)
        else:
            return vmin + value * (vmax - vmin)


00673     def autoscale(self, A):
        '''
        Set *vmin*, *vmax* to min, max of *A*.
        '''
        self.vmin = ma.minimum(A)
        self.vmax = ma.maximum(A)

    def autoscale_None(self, A):
        ' autoscale only None-valued vmin or vmax'
        if self.vmin is None: self.vmin = ma.minimum(A)
        if self.vmax is None: self.vmax = ma.maximum(A)

    def scaled(self):
        'return true if vmin and vmax set'
        return (self.vmin is not None and self.vmax is not None)

00689 class LogNorm(Normalize):
    """
    Normalize a given value to the 0-1 range on a log scale
    """
    def __call__(self, value, clip=None):
        if clip is None:
            clip = self.clip

        if cbook.iterable(value):
            vtype = 'array'
            val = ma.asarray(value).astype(np.float)
        else:
            vtype = 'scalar'
            val = ma.array([value]).astype(np.float)

        self.autoscale_None(val)
        vmin, vmax = self.vmin, self.vmax
        if vmin > vmax:
            raise ValueError("minvalue must be less than or equal to maxvalue")
        elif vmin<=0:
            raise ValueError("values must all be positive")
        elif vmin==vmax:
            return 0.0 * val
        else:
            if clip:
                mask = ma.getmask(val)
                val = ma.array(np.clip(val.filled(vmax), vmin, vmax),
                                mask=mask)
            result = (ma.log(val)-np.log(vmin))/(np.log(vmax)-np.log(vmin))
        if vtype == 'scalar':
            result = result[0]
        return result

    def inverse(self, value):
        if not self.scaled():
            raise ValueError("Not invertible until scaled")
        vmin, vmax = self.vmin, self.vmax

        if cbook.iterable(value):
            val = ma.asarray(value)
            return vmin * ma.power((vmax/vmin), val)
        else:
            return vmin * pow((vmax/vmin), value)

00733 class BoundaryNorm(Normalize):
    '''
    Generate a colormap index based on discrete intervals.

    Unlike :class:`Normalize` or :class:`LogNorm`,
    :class:`BoundaryNorm` maps values to integers instead of to the
    interval 0-1.

    Mapping to the 0-1 interval could have been done via
    piece-wise linear interpolation, but using integers seems
    simpler, and reduces the number of conversions back and forth
    between integer and floating point.
    '''
00746     def __init__(self, boundaries, ncolors, clip=False):
        '''
        *boundaries*
            a monotonically increasing sequence
        *ncolors*
            number of colors in the colormap to be used

        If::

            b[i] <= v < b[i+1]

        then v is mapped to color j;
        as i varies from 0 to len(boundaries)-2,
        j goes from 0 to ncolors-1.

        Out-of-range values are mapped to -1 if low and ncolors
        if high; these are converted to valid indices by
        :meth:`Colormap.__call__` .
        '''
        self.clip = clip
        self.vmin = boundaries[0]
        self.vmax = boundaries[-1]
        self.boundaries = np.asarray(boundaries)
        self.N = len(self.boundaries)
        self.Ncmap = ncolors
        if self.N-1 == self.Ncmap:
            self._interp = False
        else:
            self._interp = True

    def __call__(self, x, clip=None):
        if clip is None:
            clip = self.clip
        x = ma.asarray(x)
        mask = ma.getmaskarray(x)
        xx = x.filled(self.vmax+1)
        if clip:
            np.clip(xx, self.vmin, self.vmax)
        iret = np.zeros(x.shape, dtype=np.int16)
        for i, b in enumerate(self.boundaries):
            iret[xx>=b] = i
        if self._interp:
            iret = (iret * (float(self.Ncmap-1)/(self.N-2))).astype(np.int16)
        iret[xx<self.vmin] = -1
        iret[xx>=self.vmax] = self.Ncmap
        ret = ma.array(iret, mask=mask)
        if ret.shape == () and not mask:
            ret = int(ret)  # assume python scalar
        return ret

    def inverse(self, value):
        return ValueError("BoundaryNorm is not invertible")


00800 class NoNorm(Normalize):
    '''
    Dummy replacement for Normalize, for the case where we
    want to use indices directly in a
    :class:`~matplotlib.cm.ScalarMappable` .
    '''
    def __call__(self, value, clip=None):
        return value

    def inverse(self, value):
        return value

# compatibility with earlier class names that violated convention:
normalize = Normalize
no_norm = NoNorm

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