Script created by Nicolas P. Rougier to visualize 2D numpy arrays on terminal

numpy_termshow.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Terminal visualization of 2D numpy arrays
# Copyright (c) 2009  Nicolas P. Rougier
#
# This program is free software: you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free Software
# Foundation, either version 3 of the License, or (at your option) any later
# version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with
# this program.  If not, see <http://www.gnu.org/licenses/>.
# ------------------------------------------------------------------------------
""" Terminal visualization of 2D numpy arrays
    Using extended color capability of terminal (256 colors), the imshow function
    renders a 2D numpy array within terminal.
"""
import sys
import numpy

class ColorMap:
    ''' A colormap is used to map scalar values to colors. It is build by
        adding couples of (value,color) where value must be between 0 and 1.
        The 'scale' method allows to specify the range of the colormap and
        the 'color' method then returns a color for any value. '''

    def __init__ (self, colors):
        self.colors = colors
        self.min    = 0
        self.max    = 1

    def scale (self, min, max):
        self.min, self.max = min,max

    def color (self, value):
        ''' Return the color corresponding to value. '''
        if not len(self.colors):
            return (0,0,0)
        elif len(self.colors) == 1:
            return self.colors[0][1]
        elif value < self.min:
            return self.colors[0][1]
        elif value > self.max:
            return self.colors[-1][1]
        value = (value-self.min)/(self.max-self.min)
        sup_color = self.colors[0]
        inf_color = self.colors[-1]
        for i in range (len(self.colors)-1):
            if value < self.colors[i+1][0]:
                inf_color = self.colors[i]
                sup_color = self.colors[i+1]
                break
        r = (value-inf_color[0]) / (sup_color[0] - inf_color[0])
        if r < 0: r = -r
        color = [sup_color[1][0]*r + inf_color[1][0]*(1-r),
                 sup_color[1][1]*r + inf_color[1][1]*(1-r),
                 sup_color[1][2]*r + inf_color[1][2]*(1-r)]
        return color

# Some colormaps
CM_IceAndFire = ColorMap([(0.00, (0.0, 0.0, 1.0)),
                         (0.25, (0.0, 0.5, 1.0)),
                         (0.50, (1.0, 1.0, 1.0)),
                         (0.75, (1.0, 1.0, 0.0)),
                         (1.00, (1.0, 0.0, 0.0))])
CM_Ice = ColorMap([(0.00, (0.0, 0.0, 1.0)),
                   (0.50, (0.5, 0.5, 1.0)),
                   (1.00, (1.0, 1.0, 1.0))])
CM_Fire = ColorMap([(0.00, (1.0, 1.0, 1.0)),
                    (0.50, (1.0, 1.0, 0.0)),
                    (1.00, (1.0, 0.0, 0.0))])
CM_Hot = ColorMap([(0.00, (0.0, 0.0, 0.0)),
                   (0.33, (1.0, 0.0, 0.0)),
                   (0.66, (1.0, 1.0, 0.0)),
                   (1.00, (1.0, 1.0, 1.0))])
CM_Grey = ColorMap([(0.00, (0.0, 0.0, 0.0)),
                    (1.00, (1.0, 1.0, 1.0))])



def imshow (Z, vmin=None, vmax=None, cmap=CM_Hot, show_cmap=True):
    ''' Show a 2D numpy array using terminal colors '''

    if len(Z.shape) != 2:
        print "Cannot display non 2D array"
        return

    vmin = vmin or Z.min()
    vmax = vmax or Z.max()
    cmap.scale (vmin, vmax)

    # Build initialization string that setup terminal colors
    init = ''
    for i in range(240):
        v = cmap.min + (i/240.0)* (cmap.max - cmap.min)
        r,g,b = cmap.color (v)
        init += "\x1b]4;%d;rgb:%02x/%02x/%02x\x1b\\" % (16+i, int(r*255),int(g*255),int(b*255))

    # Build array data string
    data = ''
    for i in range(Z.shape[0]):
        for j in range(Z.shape[1]):
            c = 16 + int( ((Z[Z.shape[0]-i-1,j]-cmap.min) / (cmap.max-cmap.min))*239)
            if (c < 16):
                c=16
            elif (c > 255):
                c=255
            data += "\x1b[48;5;%dm  " % c
            u = cmap.max - (i/float(Z.shape[0]-1)) * ((cmap.max-cmap.min))
        if show_cmap:
            data += "\x1b[0m  "
            data += "\x1b[48;5;%dm  " % (16 + (1-i/float(Z.shape[0]))*239)
            data += "\x1b[0m %+.2f" % u
        data += "\n"

    sys.stdout.write(init+'\n')
    sys.stdout.write(data)


if __name__ == '__main__':
    def func3(x,y):
        return (1- x/2 + x**5 + y**3)*numpy.exp(-x**2-y**2)
    dx, dy = .2, .2
    x = numpy.arange(-3.0, 3.0, dx)
    y = numpy.arange(-3.0, 3.0, dy)
    X,Y = numpy.meshgrid(x, y)
    Z = numpy.array (func3(X, Y))
    imshow (Z, cmap=CM_Hot)