text_utils.py

from __future__ import division
from __future__ import print_function

import scipy
import numpy as np
import matplotlib.pyplot as plt 
import scipy.io as sio
import os.path as osp
import random, os
import cv2
# import cPickle as cp
import pickle as cp
import scipy.signal as ssig
import scipy.stats as sstat
import pygame, pygame.locals
from pygame import freetype
#import Image
from PIL import Image
import math
from common import *

xrange = range


def sample_weighted(p_dict):
    ps = list(p_dict.keys())
    return p_dict[np.random.choice(ps,p=ps)]

def my_sample_weighted(p_dict):
    keys = list(p_dict.keys())
    ps = list(p_dict.values())
    return keys[np.random.choice(len(keys), p=ps)]

def move_bb(bbs, t):
    """
    Translate the bounding-boxes in by t_x,t_y.
    BB : 2x4xn
    T  : 2-long np.array
    """
    return bbs + t[:,None,None]

def crop_safe(arr, rect, bbs=[], pad=0):
    """
    ARR : arr to crop
    RECT: (x,y,w,h) : area to crop to
    BBS : nx4 xywh format bounding-boxes
    PAD : percentage to pad

    Does safe cropping. Returns the cropped rectangle and
    the adjusted bounding-boxes
    """
    rect = np.array(rect)
    rect[:2] -= pad
    rect[2:] += 2*pad
    v0 = [max(0,rect[0]), max(0,rect[1])]
    v1 = [min(arr.shape[0], rect[0]+rect[2]), min(arr.shape[1], rect[1]+rect[3])]
    arr = arr[v0[0]:v1[0],v0[1]:v1[1],...]
    if len(bbs) > 0:
        for i in xrange(len(bbs)):
            bbs[i,0] -= v0[0]
            bbs[i,1] -= v0[1]
        return arr, bbs
    else:
        return arr


class BaselineState(object):
    curve = lambda this, a: lambda x: a*x*x
    differential = lambda this, a: lambda x: 2*a*x
    a = [2, 0.05]

    # PARAM: curve
    def get_sample(self):
        """
        Returns the functions for the curve and differential for a and b
        """
        sgn = 1.0
        if np.random.rand() < 0.5:
            sgn = -1

        a = self.a[1]*np.random.randn() + sgn*self.a[0]
        return {
            'curve': self.curve(a),
            'diff': self.differential(a),
        }

class RenderFont(object):
    """
    Outputs a rasterized font sample.
        Output is a binary mask matrix cropped closesly with the font.
        Also, outputs ground-truth bounding boxes and text string
    """

    def __init__(self, data_dir='data'):
        pygame.init()

        # distribution over the type of text:
        # whether to get a single word, paragraph or a line:
        self.p_text = {0.0 : 'WORD',
                       0.0 : 'LINE',
                       1.0 : 'PARA'}

        ## TEXT PLACEMENT PARAMETERS:
        self.f_shrink = 0.90
        self.max_shrink_trials = 5 # 0.9^5 ~= 0.6
        # the minimum number of characters that should fit in a mask
        # to define the maximum font height.
        self.min_nchar = 1
        self.min_font_h = 16 #px : 0.6*12 ~ 7px <= actual minimum height
        self.max_font_h = 120 #px
        self.p_flat = 0.10

        # curved baseline:
        self.p_curved = 1.0
        self.baselinestate = BaselineState()

        # text-source : gets english text:
        self.text_source = TextSource(min_nchar=self.min_nchar,
                                      fn=osp.join(data_dir,'newsgroup/newsgroup.txt'))

        # get font-state object:
        self.font_state = FontState(data_dir)

    def render_multiline(self,font,text):
        """
        renders multiline TEXT on the pygame surface SURF with the
        font style FONT.
        A new line in text is denoted by \n, no other characters are 
        escaped. Other forms of white-spaces should be converted to space.

        returns the updated surface, words and the character bounding boxes.
        """
        # get the number of lines
        lines = text.split('\n')
        lengths = [len(l) for l in lines]

        # font parameters:
        line_spacing = font.get_sized_height() + 1
        # PARAM: line spacing
        
        # initialize the surface to proper size:
        line_bounds = font.get_rect(lines[np.argmax(lengths)])
        fsize = (round(5.0*line_bounds.width), round(1.25*line_spacing*len(lines)))
        surf = pygame.Surface(fsize, pygame.locals.SRCALPHA, 32)

        bbs = []
        space = font.get_rect('O')
        # PARAM: space width
        if np.random.rand() < 1:
            spacewidth = space.width * np.clip(np.random.randn()*0.5+0.5, 0.2, 1.5)
        else:
            spacewidth = space.width * np.clip(np.random.randn()*0.5+2.0, 1.0, 3.0)
        x, y = 0, 0
        for l in lines:
            x = 0 # carriage-return
            y += line_spacing # line-feed

            for ch in l: # render each character
                if ch.isspace(): # just shift
                    x += spacewidth
                else:
                    # render the character
                    ch_bounds = font.render_to(surf, (x,y), ch)
                    ch_bounds.x = x + ch_bounds.x
                    ch_bounds.y = y - ch_bounds.y
                    x += ch_bounds.width
                    bbs.append(np.array(ch_bounds))

        # get the union of characters for cropping:
        r0 = pygame.Rect(bbs[0])
        rect_union = r0.unionall(bbs)

        # get the words:
        words = ' '.join(text.split())

        # crop the surface to fit the text:
        bbs = np.array(bbs)
        surf_arr, bbs = crop_safe(pygame.surfarray.pixels_alpha(surf), rect_union, bbs, pad=5)
        surf_arr = surf_arr.swapaxes(0,1)
        # self.visualize_bb(surf_arr,bbs)
        return surf_arr, words, bbs, None

    def render_curved(self, font, word_text):
        """
        use curved baseline for rendering word
        """
        wl = len(word_text)
        isword = word_text.find('\n') == -1 \
            and len(word_text.split()) <= 5 \
            and len(word_text)/len(word_text.split()) > 2

        # do curved iff, the length of the word <= 10
        if not isword or wl > 20 or np.random.rand() > self.p_curved:
            #return self.render_multiline(font, word_text)
            return None, None, None, None
        # create the surface:
        lspace = font.get_sized_height() + 1
        try:
            lbound = font.get_rect(word_text)
        except:
            return None, None, None, None
        fsize = (round(3.0*lbound.width), round(lspace*10))
        surf = pygame.Surface(fsize, pygame.locals.SRCALPHA, 32)

        # rho = (2 + np.random.rand()*10)*lbound.width
        rho = lbound.width * (1.0 + np.random.rand()**3 * 3)
        rho_signal = -1 if np.random.rand() < 0.5 else 1
        ravg = (rho - math.sqrt(rho*rho - lbound.width*lbound.width)) / 2
        yfunc = lambda x: (math.sqrt(rho*rho - x*x) - ravg) * rho_signal
        tfunc = lambda x: -int(round(math.degrees(math.asin(x/rho)))) * rho_signal

        # baseline state
        mid_idx = wl//2
        # BS = self.baselinestate.get_sample()
        # curve = [BS['curve'](i-mid_idx) for i in xrange(wl)]
        # curve[mid_idx] = -np.sum(curve) / (wl-1)
        # rots  = [-int(math.degrees(math.atan(BS['diff'](i-mid_idx)/(font.size/2)))) for i in xrange(wl)]

        bbs = []
        rotated_angles = []
        # place middle char
        rect = font.get_rect(word_text[mid_idx])
        rect.centerx = surf.get_rect().centerx
        rect.centery = fsize[1] / 2 + rect.height + yfunc(0)
        # rect.centery +=  yfunc(0)
        try:
            rotated_angle = tfunc(0)
            ch_bounds = font.render_to(surf, rect, word_text[mid_idx], rotation=rotated_angle)
        except ValueError:
            rotated_angle = 0
            ch_bounds = font.render_to(surf, rect, word_text[mid_idx])

        ch_bounds.x = rect.x + ch_bounds.x
        ch_bounds.y = rect.y - ch_bounds.y
        mid_ch_bb = np.array(ch_bounds)

        # render chars to the left and right:
        last_rect = rect
        ch_idx = []
        # trueindex = 0
        olddeltax = 0.0

        if word_text[mid_idx] != ' ':
            bbs.append(ch_bounds)
            rotated_angles.append(rotated_angle)

        for i in xrange(wl):
            #skip the middle character
            if i==mid_idx: 
                # if word_text[mid_idx] != ' ':
                    # bbs.append(mid_ch_bb)
                    # ch_idx.append(trueindex)
                    # trueindex += 1
                continue

            if i < mid_idx: #left-chars
                i = mid_idx-1-i
            elif i==mid_idx+1: #right-chars begin
                last_rect = rect
                olddeltax = 0.0

            ch = word_text[i]

            newrect = font.get_rect(ch)
            newrect.y = last_rect.y
            if i > mid_idx:
                newrect.topleft = (last_rect.topright[0]+2, newrect.topleft[1])
            else:
                newrect.topright = (last_rect.topleft[0]-2, newrect.topleft[1])
            deltax = surf.get_rect().centerx-newrect.centerx
            # newrect.centery = max(newrect.height, min(fsize[1] - newrect.height, surf.get_rect().centery + rect.height + yfunc(deltax)))
            # newrect.centery = surf.get_rect().centery + rect.height
            newrect.centery += yfunc(deltax) - yfunc(olddeltax)
            olddeltax = deltax
            try:
                rotated_angle = tfunc(deltax)
                bbrect = font.render_to(surf, newrect, ch, rotation=rotated_angle)
            except ValueError:
                rotated_angle = 0
                bbrect = font.render_to(surf, newrect, ch)
            bbrect.x = newrect.x + bbrect.x
            bbrect.y = newrect.y - bbrect.y
            if ch != ' ':
                if i > mid_idx:
                    bbs.append(np.array(bbrect))
                    rotated_angles.append(rotated_angle)
                else:
                    bbs = [np.array(bbrect)] + bbs
                    rotated_angles = [rotated_angle] + rotated_angles
                # ch_idx.append(trueindex)
                # bbs.append(np.array(bbrect))
                # trueindex += 1
            last_rect = newrect
        
        # correct the bounding-box order:
        # bbs_sequence_order = [None for i in ch_idx]
        # for idx,i in enumerate(ch_idx):
        #     bbs_sequence_order[i] = bbs[idx]
        # bbs = bbs_sequence_order

        # get the union of characters for cropping:
        r0 = pygame.Rect(bbs[0])
        rect_union = r0.unionall(bbs)

        # crop the surface to fit the text:
        bbs = np.array(bbs)
        # print(bbs.shape)
        for bb in bbs:
            if bb[0] < 0 or bb[1] < 0 or bb[2]+bb[0] > fsize[0] or bb[3]+bb[1] > fsize[1]:
                return None, None, None, None
        surf_arr, bbs = crop_safe(pygame.surfarray.pixels_alpha(surf), rect_union, bbs, pad=5)
        surf_arr = surf_arr.swapaxes(0,1)
        return surf_arr, word_text, bbs, rotated_angles


    def get_nline_nchar(self,mask_size,font_height,font_width):
        """
        Returns the maximum number of lines and characters which can fit
        in the MASK_SIZED image.
        """
        H,W = mask_size
        nline = int(np.ceil(H/(2*font_height)))
        nchar = int(np.floor(W/font_width))
        return nline,nchar

    def place_text(self, text_arrs, back_arr, bbs):
        areas = [-np.prod(ta.shape) for ta in text_arrs]
        order = np.argsort(areas)

        locs = [None for i in range(len(text_arrs))]
        out_arr = np.zeros_like(back_arr)
        for i in order:            
            ba = np.clip(back_arr.copy().astype(np.float), 0, 255)
            ta = np.clip(text_arrs[i].copy().astype(np.float), 0, 255)
            ba[ba > 127] = 1e8
            intersect = ssig.fftconvolve(ba,ta[::-1,::-1],mode='valid')
            safemask = intersect < 1e8

            if not np.any(safemask): # no collision-free position:
                #warn("COLLISION!!!")
                return back_arr,locs[:i],bbs[:i],order[:i]

            minloc = np.transpose(np.nonzero(safemask))
            loc = minloc[np.random.choice(minloc.shape[0]),:]
            locs[i] = loc

            # update the bounding-boxes:
            bbs[i] = move_bb(bbs[i],loc[::-1])

            # blit the text onto the canvas
            w,h = text_arrs[i].shape
            out_arr[loc[0]:loc[0]+w,loc[1]:loc[1]+h] += text_arrs[i]

        return out_arr, locs, bbs, order

    def robust_HW(self,mask):
        m = mask.copy()
        m = (~mask).astype('float')/255
        rH = np.median(np.sum(m,axis=0))
        rW = np.median(np.sum(m,axis=1))
        return rH,rW

    def sample_font_height_px(self,h_min,h_max):
        if np.random.rand() < self.p_flat:
            rnd = np.random.rand()
        else:
            rnd = np.random.beta(2.0,2.0)

        h_range = h_max - h_min
        f_h = np.floor(h_min + h_range*rnd)
        return f_h

    def bb_xywh2coords(self,bbs):
        """
        Takes an nx4 bounding-box matrix specified in x,y,w,h
        format and outputs a 2x4xn bb-matrix, (4 vertices per bb).
        """
        n,_ = bbs.shape
        coords = np.zeros((2,4,n))
        for i in xrange(n):
            coords[:,:,i] = bbs[i,:2][:,None]
            coords[0,1,i] += bbs[i,2]
            coords[:,2,i] += bbs[i,2:4]
            coords[1,3,i] += bbs[i,3]
        return coords


    # def rotate_boxes(self, bbs, rots):
    #     """
    #     Rotate the bbs giving the rots.
    #     Args:
    #         bbs list: [(x,y,w,h), ...]
    #         rots list: [float]
    #     Returns:
    #         rotated_bbs list: [[4x2], ...]
    #     """
    #     if rots is None: # in render_multiline(), no rotation
    #         new_bbs = []
    #         for bb in bbs:
    #             pt1 = [bb[0], bb[1]]
    #             pt2 = [bb[0]+bb[2], bb[1]]
    #             pt3 = [bb[0]+bb[2], bb[1]+bb[3]]
    #             pt4 = [bb[0], bb[1]+bb[3]]
    #             pts = np.array([pt1, pt2, pt3, pt4])
    #             new_bbs.append(pts)
    #         return new_bbs
    #     else:
    #         rotated_bbs = []
    #         for bb, rot in zip(bbs, rots):
    #             pt1 = [bb[0], bb[1]]
    #             pt2 = [bb[0]+bb[2], bb[1]]
    #             pt3 = [bb[0]+bb[2], bb[1]+bb[3]]
    #             pt4 = [bb[0], bb[1]+bb[3]]
    #             center_pt = [bb[0]+bb[2]/2, bb[1]+bb[3]/2]
    #             pts = np.array([pt1, pt2, pt3, pt4])
    #             pts = np.expand_dims(pts, 0)
    #             M = cv2.getRotationMatrix2D((center_pt[0], center_pt[1]), rot, 1.0)
    #             padded_boxes = np.insert(pts, 2, 1, axis=2) # [1, 4, 3]
    #             warped_boxes = np.matmul(padded_boxes, M.transpose())
    #             warped_boxes = warped_boxes.astype(np.int)
    #             rotated_bbs.append(warped_boxes)
    #         return rotated_bbs


    def rotate_boxes(self, bbs, rots):
        """
        Rotate the bbs giving the rots.
        Args:
            bbs array: [2, 4, n]
            rots list: [float]
        Returns:
            rotated_bbs array: [2, 4, n]
        """
        if rots is None:
            return bbs
        else:
            n = bbs.shape[-1]
            rotated_bbs = np.zeros((2,4,n))
            for i in range(n):
                pts = bbs[:,:,i] # [2, 4]
                centerx = np.sum(pts[0,:]) / 4.
                centery = np.sum(pts[1,:]) / 4.
                # pts = np.expand_dims(pts, 0)
                # pts = np.transpose(pts, (0, 2, 1)) # [1, 4, 2]
                # pts = np.insert(pts, 2, 1, axis=2) # [1, 4, 3]
                pts = np.transpose(pts, (1,0)) # [4, 2]
                pts = np.insert(pts, 2, 1, axis=1) # [4, 3]
                M = cv2.getRotationMatrix2D((centerx, centery), rots[i], 1.0)
                rotated_bb = np.matmul(pts, M.transpose())
                rotated_bb = rotated_bb.astype(np.int)
                rotated_bbs[:,:,i] = rotated_bb.transpose()
            return rotated_bbs


    def render_sample(self,font,mask):
        """
        Places text in the "collision-free" region as indicated
        in the mask -- 255 for unsafe, 0 for safe.
        The text is rendered using FONT, the text content is TEXT.
        """
        #H,W = mask.shape
        H,W = self.robust_HW(mask)
        f_asp = self.font_state.get_aspect_ratio(font)

        # find the maximum height in pixels:
        max_font_h = min(0.9*H, (1/f_asp)*W/(self.min_nchar+1))
        max_font_h = min(max_font_h, self.max_font_h)
        if max_font_h < self.min_font_h: # not possible to place any text here
            return #None

        # let's just place one text-instance for now
        ## TODO : change this to allow multiple text instances?
        i = 0
        while i < self.max_shrink_trials and max_font_h > self.min_font_h:
            # if i > 0:
            #     print colorize(Color.BLUE, "shrinkage trial : %d"%i, True)

            # sample a random font-height:
            f_h_px = self.sample_font_height_px(self.min_font_h, max_font_h)
            #print "font-height : %.2f (min: %.2f, max: %.2f)"%(f_h_px, self.min_font_h,max_font_h)
            # convert from pixel-height to font-point-size:
            f_h = self.font_state.get_font_size(font, f_h_px)

            # update for the loop
            max_font_h = f_h_px 
            i += 1

            font.size = f_h # set the font-size

            # compute the max-number of lines/chars-per-line:
            nline,nchar = self.get_nline_nchar(mask.shape[:2],f_h,f_h*f_asp)
            #print "  > nline = %d, nchar = %d"%(nline, nchar)

            assert nline >= 1 and nchar >= self.min_nchar

            # sample text:
            text_type = sample_weighted(self.p_text)
            text = self.text_source.sample(nline,nchar,text_type)
            if len(text)==0 or np.any([len(line)==0 for line in text]):
                continue
            #print colorize(Color.GREEN, text)

            # render the text:
            txt_arr,txt,bb,rots = self.render_curved(font, ' '.join(text.split('&')))
            if bb is None:
                continue

            bb = self.bb_xywh2coords(bb)

            # make sure that the text-array is not bigger than mask array:
            if np.any(np.r_[txt_arr.shape[:2]] > np.r_[mask.shape[:2]]):
                #warn("text-array is bigger than mask")
                continue

            # position the text within the mask:
            text_mask,loc,bb, _ = self.place_text([txt_arr], mask, [bb])
            if rots is not None and len(bb) > 0: # bb size: [2, 4, n]
                assert(bb[0].shape[-1] == len(rots))
            if len(bb) > 0:
                rotated_bbs = self.rotate_boxes(bb[0], rots)
            if len(loc) > 0:#successful in placing the text collision-free:
                # return text_mask,loc[0],bb[0],''.join(text.split('&'))
                return text_mask, loc[0], rotated_bbs, ''.join(text.split('&'))
        return #None


    def visualize_bb(self, text_arr, bbs):
        ta = text_arr.copy()
        for r in bbs:
            cv2.rectangle(ta, (r[0],r[1]), (r[0]+r[2],r[1]+r[3]), color=128, thickness=1)
        plt.imshow(ta,cmap='gray')
        plt.show()

    def visualize_rotated_bb(self, text_arr, bbs):
        ta = text_arr.copy()
        for bb in bbs:
            bb = np.array(bb, np.int)
            bb = bb.reshape((-1,1,2))
            cv2.polylines(ta,[bb],True,color=128,thickness=1)
        plt.imshow(ta,cmap='gray')
        plt.show()

    def visualize_text_mask_bb(self, text_mask, bbs):
        tm = text_mask.copy()
        num_words = len(bbs)
        for i in range(num_words):
            bbs_i = bbs[i]
            num_chars = bbs_i.shape[-1]
            bbs_i = np.transpose(bbs_i, (2,1,0)).astype(np.uint8)
            print(len(list(bbs_i)))
            cv2.drawContours(tm, list(bbs_i), -1, (0,255,0), 3)
        plt.imshow(tm,cmap='gray')
        plt.show()


class FontState(object):
    """
    Defines the random state of the font rendering  
    """
    size = [50, 10]  # normal dist mean, std
    underline = 0.05
    strong = 0.5
    oblique = 0.2
    wide = 0.5
    strength = [0.05, 0.1]  # uniform dist in this interval
    underline_adjustment = [1.0, 2.0]  # normal dist mean, std
    kerning = [2, 5, 0, 20]  # beta distribution alpha, beta, offset, range (mean is a/(a+b))
    border = 0.25
    random_caps = -1 ## don't recapitalize : retain the capitalization of the lexicon
    capsmode = [str.lower, str.upper, str.capitalize]  # lower case, upper case, proper noun
    curved = 0.2
    random_kerning = 0.2
    random_kerning_amount = 0.1


    def __init__(self, data_dir='data'):

        char_freq_path = osp.join(data_dir, 'models/char_freq.cp')        
        font_model_path = osp.join(data_dir, 'models/font_px2pt.cp')

        # get character-frequencies in the English language:
        with open(char_freq_path,'rb') as f:
            char_freq = cp.load(f, encoding='bytes')
        self.char_freq = {}
        for k,v in char_freq.items():
            self.char_freq[k.decode('utf-8')] = v

        # get the model to convert from pixel to font pt size:
        with open(font_model_path,'rb') as f:
            self.font_model = cp.load(f)

        # get the names of fonts to use:
        self.FONT_LIST = osp.join(data_dir, 'fonts/fontlist.txt')
        self.fonts = [os.path.join(data_dir,'fonts',f.strip()) for f in open(self.FONT_LIST)]


    def get_aspect_ratio(self, font, size=None):
        """
        Returns the median aspect ratio of each character of the font.
        """
        if size is None:
            size = 12 # doesn't matter as we take the RATIO
        chars = ''.join(self.char_freq.keys())
        w = np.array(self.char_freq.values())

        # get the [height,width] of each character:
        try:
            sizes = font.get_metrics(chars,size)
            good_idx = [i for i in xrange(len(sizes)) if sizes[i] is not None]
            sizes,w = [sizes[i] for i in good_idx], w[good_idx]
            sizes = np.array(sizes).astype('float')[:,[3,4]]        
            r = np.abs(sizes[:,1]/sizes[:,0]) # width/height
            good = np.isfinite(r)
            r = r[good]
            w = w[good]
            w /= np.sum(w)
            r_avg = np.sum(w*r)
            return r_avg
        except Exception:
            return 1.0

    def get_font_size(self, font, font_size_px):
        """
        Returns the font-size which corresponds to FONT_SIZE_PX pixels font height.
        """
        m = self.font_model[font.name]
        return m[0]*font_size_px + m[1] #linear model


    def sample(self):
        """
        Samples from the font state distribution
        """
        return {
            'font': self.fonts[int(np.random.randint(0, len(self.fonts)))],
            'size': self.size[1]*np.random.randn() + self.size[0],
            'underline': np.random.rand() < self.underline,
            'underline_adjustment': max(2.0, min(-2.0, self.underline_adjustment[1]*np.random.randn() + self.underline_adjustment[0])),
            'strong': np.random.rand() < self.strong,
            'oblique': np.random.rand() < self.oblique,
            'strength': (self.strength[1] - self.strength[0])*np.random.rand() + self.strength[0],
            'char_spacing': int(self.kerning[3]*(np.random.beta(self.kerning[0], self.kerning[1])) + self.kerning[2]),
            'border': np.random.rand() < self.border,
            'random_caps': np.random.rand() < self.random_caps,
            'capsmode': random.choice(self.capsmode),
            'curved': np.random.rand() < self.curved,
            'random_kerning': np.random.rand() < self.random_kerning,
            'random_kerning_amount': self.random_kerning_amount,
        }

    def init_font(self,fs):
        """
        Initializes a pygame font.
        FS : font-state sample
        """

        # PARAM: underline, strong, oblique, strength
        font = freetype.Font(fs['font'], size=fs['size'])
        font.underline = fs['underline']
        font.underline_adjustment = fs['underline_adjustment']
        font.strong = fs['strong']
        font.oblique = fs['oblique']
        font.strength = fs['strength']
        char_spacing = fs['char_spacing']
        font.antialiased = True
        font.origin = True
        return font


class TextSource(object):
    """
    Provides text for words, paragraphs, sentences.
    """
    def __init__(self, min_nchar, fn):
        """
        TXT_FN : path to file containing text data.
        """
        self.min_nchar = min_nchar
        self.fdict = {'WORD':self.sample_word,
                      'LINE':self.sample_line,
                      'PARA':self.sample_para}

        with open(fn,'r') as f:
            self.txt = [l.strip() for l in f.readlines()]

        # distribution over line/words for LINE/PARA:
        self.p_line_nline = np.array([0.85, 0.10, 0.05])
        self.p_line_nword = [4,3,12]  # normal: (mu, std)
        self.p_para_nline = [1.0,1.0]#[1.7,3.0] # beta: (a, b), max_nline
        self.p_para_nword = [1.7,3.0,10] # beta: (a,b), max_nword

        # probability to center-align a paragraph:
        self.center_para = 0.5


    def check_symb_frac(self, txt, f=0.35):
        """
        T/F return : T iff fraction of symbol/special-charcters in
                     txt is less than or equal to f (default=0.25).
        """
        return np.sum([not ch.isalnum() for ch in txt])/(len(txt)+0.0) <= f

    def is_good(self, txt, f=0.35):
        """
        T/F return : T iff the lines in txt (a list of txt lines)
                     are "valid".
                     A given line l is valid iff:
                         1. It is not empty.
                         2. symbol_fraction > f
                         3. Has at-least self.min_nchar characters
                         4. Not all characters are i,x,0,O,-
        """
        def is_txt(l):
            char_ex = ['i','I','o','O','0','-']
            chs = [ch in char_ex for ch in l]
            return not np.all(chs)

        return [ (len(l)> self.min_nchar
                 and self.check_symb_frac(l,f)
                 and is_txt(l)) for l in txt ]

    def center_align(self, lines):
        """
        PADS lines with space to center align them
        lines : list of text-lines.
        """
        ls = [len(l) for l in lines]
        max_l = max(ls)
        for i in xrange(len(lines)):
            l = lines[i].strip()
            dl = max_l-ls[i]
            lspace = dl//2
            rspace = dl-lspace
            lines[i] = ' '*lspace+l+' '*rspace
        return lines

    def get_lines(self, nline, nword, nchar_max, f=0.35, niter=100):
        def h_lines(niter=100):
            lines = ['']
            iter = 0
            while not np.all(self.is_good(lines,f)) and iter < niter:
                iter += 1
                line_start = np.random.choice(len(self.txt)-nline)
                lines = [self.txt[line_start+i] for i in range(nline)]
            return lines

        lines = ['']
        iter = 0
        while not np.all(self.is_good(lines,f)) and iter < niter:
            iter += 1
            lines = h_lines(niter=100)
            # get words per line:
            nline = len(lines)
            for i in range(nline):
                words = lines[i].split()
                dw = len(words)-nword[i]
                if dw > 0:
                    first_word_index = random.choice(range(dw+1))
                    lines[i] = ' '.join(words[first_word_index:first_word_index+nword[i]])

                while len(lines[i]) > nchar_max: #chop-off characters from end:
                    if not np.any([ch.isspace() for ch in lines[i]]):
                        lines[i] = ''
                    else:
                        lines[i] = lines[i][:len(lines[i])-lines[i][::-1].find(' ')].strip()
        
        if not np.all(self.is_good(lines,f)):
            return #None
        else:
            return lines

    def sample(self, nline_max,nchar_max,kind='WORD'):
        return self.fdict[kind](nline_max,nchar_max)
        
    def sample_word(self,nline_max,nchar_max,niter=100):
        # print("sample_word")

        rand_line = self.txt[np.random.choice(len(self.txt))]                
        words = rand_line.split()
        rand_word = random.choice(words)

        iter = 0
        while iter < niter and (not self.is_good([rand_word])[0] or len(rand_word)>nchar_max):
            rand_line = self.txt[np.random.choice(len(self.txt))]                
            words = rand_line.split()
            rand_word = random.choice(words)
            iter += 1

        if not self.is_good([rand_word])[0] or len(rand_word)>nchar_max:
            return []
        else:
            return rand_word


    def sample_line(self,nline_max,nchar_max):
        # print("sample_line")

        nline = nline_max+1
        while nline > nline_max:
            nline = np.random.choice([1,2,3], p=self.p_line_nline)

        # get number of words:
        nword = [self.p_line_nword[2]*sstat.beta.rvs(a=self.p_line_nword[0], b=self.p_line_nword[1])
                 for _ in xrange(nline)]
        nword = [max(1,int(np.ceil(n))) for n in nword]

        lines = self.get_lines(nline, nword, nchar_max, f=0.35)
        if lines is not None:
            return '\n'.join(lines)
        else:
            return []

    def sample_para(self,nline_max,nchar_max):
        # print("sample_para")

        spacing_dict = {
            0: 0.7,
            1: 0.25,
            2: 0.05
        }

        if nchar_max == 0:
            spacing = 0
        else:
            spacing = my_sample_weighted(spacing_dict)
            while spacing+1 > nchar_max:
                spacing = my_sample_weighted(spacing_dict)

        nchar_max = nchar_max // (spacing + 1)


        # get number of lines in the paragraph:
        nline = nline_max*sstat.beta.rvs(a=self.p_para_nline[0], b=self.p_para_nline[1])
        nline = max(1, int(np.ceil(nline)))

        # get number of words:
        nword = [self.p_para_nword[2]*sstat.beta.rvs(a=self.p_para_nword[0], b=self.p_para_nword[1])
                 for _ in xrange(nline)]
        nword = [max(1,int(np.ceil(n))) for n in nword]

        lines = self.get_lines(nline, nword, nchar_max, f=0.35)
        if lines is not None:
            # center align the paragraph-text:
            if np.random.rand() < self.center_para:
                lines = self.center_align(lines)
            return ('&'*spacing).join(list('\n'.join(lines)))
        else:
            return []