form_colormap.py

import codecs
import re
import numpy as np
import matplotlib.colors as cmx

def form_colormap(filepath, proportion=True, sep=False, spacing='c'):
    '''
    read text file containing colortable, and then form the colormap according to
    the argument given.
    sample text file structure: value, R, G, B

    Parameters
    ----------
    filepath: string
        The path of the colormap txt file.
    proportion: boolean, default is True
        When proportion is True, LinearSegmentedColormap will be formed 
        by the input values.
    sep: boolean, default is False
        When sep is True, the colormap will be a set of color blocks 
        (no color gradient).
    spacing: string, default is 'c', only used when sep is False.
        When spacing is 'c', the color blocks will be equally spaced. 
        A ListedColormap will be returned.
        When spacing is 'v', the length of color blocks will be based 
        on the input values. A LinearSegmentedColormap will be returned.
    '''
    inidict = {'red':None, 'green':None, 'blue':None}
    file_object = codecs.open(filepath, mode='r', encoding='GBK')
    all_the_text = file_object.read().strip()
    file_object.close()
    contents = re.split('[\s]+', all_the_text)
    nlin = int(len(contents) / 4)
    arr = np.array(contents)
    arr = arr.reshape(nlin, 4)
    if sep == True:
        if spacing == 'c':
            ar1 = arr.transpose()
            value = []
            count = 0
            while count < len(ar1[1]):
                value.append((int(ar1[1][count]) / 255, int(ar1[2][count]) / 255, 
                              int(ar1[3][count]) / 255))
                count = count + 1
            return cmx.ListedColormap(value, 256)
        elif spacing == 'v':
            value = []
            r = []
            g = []
            b = []
            for i in arr:
                value.append(float(i[0]))
                r.append(int(i[1]) / 255)
                g.append(int(i[2]) / 255)
                b.append(int(i[3]) / 255)
                if len(value) > 1:
                    if value[-1] < value[-2]:
                        raise ValueError('Values must be in order')
            inivalue = value[0]
            maxvalue = value[-1]
            drange = maxvalue - inivalue
            rpart = []
            gpart = []
            bpart = []
            count = 0
            try:
                while count < len(value):
                    tupr = ((value[count] - inivalue) / drange, r[count], r[count])
                    tupg = ((value[count] - inivalue) / drange, g[count], g[count])
                    tupb = ((value[count] - inivalue) / drange, b[count], b[count])
                    tupra = ((value[count + 1] - inivalue-1e-5) / drange, r[count], r[count])
                    tupga = ((value[count + 1] - inivalue-1e-5) / drange, g[count], g[count])
                    tupba = ((value[count + 1] - inivalue-1e-5) / drange, b[count], b[count])
                    rpart.append(tupr)
                    rpart.append(tupra)
                    gpart.append(tupg)
                    gpart.append(tupga)
                    bpart.append(tupb)
                    bpart.append(tupba)
                    count=count+1
            except IndexError:
                rpart.append((1, r[count], r[count]))
                gpart.append((1, g[count], g[count]))
                bpart.append((1, b[count], b[count]))
            inidict['red'] = rpart
            inidict['green'] = gpart
            inidict['blue'] = bpart
            return cmx.LinearSegmentedColormap('my_colormap', inidict, 256)

    elif sep == False:
        value = []
        r = []
        g = []
        b = []
        for i in arr:
            value.append(float(i[0]))
            r.append(int(i[1]) / 255)
            g.append(int(i[2]) / 255)
            b.append(int(i[3]) / 255)
            if len(value) > 1:
                if value[-1] < value[-2]:
                    raise ValueError('Values must be in order')
        inivalue = value[0]
        maxvalue = value[-1]
        drange = maxvalue-inivalue
        rpart = []
        gpart = []
        bpart = []
        if proportion == True:
            count = 0
            while count < len(value):
                tupr = ((value[count] - inivalue) / drange, r[count], r[count])
                tupg = ((value[count] - inivalue) / drange, g[count], g[count])
                tupb = ((value[count] - inivalue) / drange, b[count], b[count])
                rpart.append(tupr)
                gpart.append(tupg)
                bpart.append(tupb)
                count=count + 1
        elif proportion == False:
            count = 0
            while count < len(value):
                tupr = (count / len(value), r[count], r[count])
                tupg = (count / len(value), g[count], g[count])
                tupb = (count / len(value), b[count], b[count])
                rpart.append(tupr)
                gpart.append(tupg)
                bpart.append(tupb)
                count = count + 1
        inidict['red'] = rpart
        inidict['green'] = gpart
        inidict['blue'] = bpart
        return cmx.LinearSegmentedColormap('my_colormap', inidict, 256)

if __name__ == '__main__':
    cdict=form_colormap('C:\\Users\\ww\\Documents\\Visual Studio 2015\\Projects\\colormap\\wxbell cape.txt', sep=True, spacing='v')