diff --git a/examples/captcha.cpp b/examples/captcha.cpp
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+/*
+ #
+ #  File        : captcha.cpp
+ #                ( C++ source file )
+ #
+ #  Description : Captcha images generator.
+ #                This file is a part of the CImg Library project.
+ #                ( http://cimg.eu )
+ #
+ #  Copyright   : David Tschumperle
+ #                ( http://tschumperle.users.greyc.fr/ )
+ #
+ #  License     : CeCILL v2.0
+ #                ( http://www.cecill.info/licences/Licence_CeCILL_V2-en.html )
+ #
+ #  This software is governed by the CeCILL  license under French law and
+ #  abiding by the rules of distribution of free software.  You can  use,
+ #  modify and/ or redistribute the software under the terms of the CeCILL
+ #  license as circulated by CEA, CNRS and INRIA at the following URL
+ #  "http://www.cecill.info".
+ #
+ #  As a counterpart to the access to the source code and  rights to copy,
+ #  modify and redistribute granted by the license, users are provided only
+ #  with a limited warranty  and the software's author,  the holder of the
+ #  economic rights,  and the successive licensors  have only  limited
+ #  liability.
+ #
+ #  In this respect, the user's attention is drawn to the risks associated
+ #  with loading,  using,  modifying and/or developing or reproducing the
+ #  software by the user in light of its specific status of free software,
+ #  that may mean  that it is complicated to manipulate,  and  that  also
+ #  therefore means  that it is reserved for developers  and  experienced
+ #  professionals having in-depth computer knowledge. Users are therefore
+ #  encouraged to load and test the software's suitability as regards their
+ #  requirements in conditions enabling the security of their systems and/or
+ #  data to be ensured and,  more generally, to use and operate it in the
+ #  same conditions as regards security.
+ #
+ #  The fact that you are presently reading this means that you have had
+ #  knowledge of the CeCILL license and that you accept its terms.
+ #
+*/
+
+#ifndef cimg_debug
+#define cimg_debug 1
+#endif
+#include "CImg.h"
+using namespace cimg_library;
+#undef min
+#undef max
+
+// Main procedure
+//----------------
+int main(int argc,char **argv) {
+
+  // Read command line parameters
+  //------------------------------
+  cimg_usage("Simple captcha generator.");
+  const char *file_o       = cimg_option("-o",(const char*)0,"Output image file");
+  const bool add_border    = cimg_option("-b",true,"Add border to captcha image");
+  const bool visu          = cimg_option("-visu",true,"Enable visualization if no output file");
+
+  // Generate captcha text (6 char max).
+  //------------------------------------
+  const char *predef_words[] = {
+    "aarrgh", "abacas", "abacus", "abakas", "abamps", "abased", "abaser", "abases", "abasia", "abated", "abater",
+    "abates", "abatis", "abator", "baobab", "barbal", "barbed", "barbel", "barber", "barbes", "barbet", "barbie",
+    "barbut", "barcas", "barded", "bardes", "bardic", "barege", "cavies", "cavils", "caving", "cavity", "cavort",
+    "cawing", "cayman", "cayuse", "ceased", "ceases", "cebids", "ceboid", "cecity", "cedarn", "dicast", "dicers",
+    "dicier", "dicing", "dicker", "dickey", "dickie", "dicots", "dictum", "didact", "diddle", "diddly", "didies",
+    "didoes", "emails", "embalm", "embank", "embark", "embars", "embays", "embeds", "embers", "emblem", "embody",
+    "emboli", "emboly", "embosk", "emboss", "fluffy", "fluids", "fluish", "fluked", "flukes", "flukey", "flumed",
+    "flumes", "flumps", "flunks", "flunky", "fluors", "flurry", "fluted", "genome", "genoms", "genres", "genros",
+    "gentes", "gentil", "gentle", "gently", "gentry", "geodes", "geodic", "geoids", "gerahs", "gerbil", "hotter",
+    "hottie", "houdah", "hounds", "houris", "hourly", "housed", "housel", "houser", "houses", "hovels", "hovers",
+    "howdah", "howdie", "inland", "inlays", "inlets", "inlier", "inmate", "inmesh", "inmost", "innage", "innate",
+    "inners", "inning", "inpour", "inputs", "inroad", "joypop", "jubbah", "jubhah", "jubile", "judder", "judged",
+    "judger", "judges", "judoka", "jugate", "jugful", "jugged", "juggle", "jugula", "knifer", "knifes", "knight",
+    "knives", "knobby", "knocks", "knolls", "knolly", "knosps", "knotty", "knouts", "knower", "knowns", "knubby",
+    "legate", "legato", "legend", "legers", "legged", "leggin", "legion", "legist", "legits", "legman", "legmen",
+    "legong", "legume", "lehuas", "mammal", "mammas", "mammee", "mammer", "mammet", "mammey", "mammie", "mammon",
+    "mamzer", "manage", "manana", "manats", "manche", "manege", "nihils", "nilgai", "nilgau", "nilled", "nimble",
+    "nimbly", "nimbus", "nimmed", "nimrod", "ninety", "ninjas", "ninons", "ninths", "niobic", "offish", "offkey",
+    "offset", "oftest", "ogdoad", "oghams", "ogival", "ogives", "oglers", "ogling", "ogress", "ogrish", "ogrism",
+    "ohmage", "papaws", "papaya", "papers", "papery", "pappus", "papula", "papule", "papyri", "parade", "paramo",
+    "parang", "paraph", "parcel", "pardah", "quasar", "quatre", "quaver", "qubits", "qubyte", "queans", "queasy",
+    "queazy", "queens", "queers", "quelea", "quells", "quench", "querns", "raised", "raiser", "raises", "raisin",
+    "raitas", "rajahs", "rakees", "rakers", "raking", "rakish", "rallye", "ralphs", "ramada", "ramate", "savory",
+    "savour", "savoys", "sawers", "sawfly", "sawing", "sawlog", "sawney", "sawyer", "saxony", "sayeds", "sayers",
+    "sayest", "sayids", "tondos", "toneme", "toners", "tongas", "tonged", "tonger", "tongue", "tonics", "tonier",
+    "toning", "tonish", "tonlet", "tonner", "tonnes", "uredia", "uredos", "ureide", "uremia", "uremic", "ureter",
+    "uretic", "urgent", "urgers", "urging", "urials", "urinal", "urines", "uropod", "villus", "vimina", "vinals",
+    "vincas", "vineal", "vinery", "vinier", "vinify", "vining", "vinous", "vinyls", "violas", "violet", "violin",
+    "webfed", "weblog", "wechts", "wedded", "wedder", "wedeln", "wedels", "wedged", "wedges", "wedgie", "weeded",
+    "weeder", "weekly", "weened", "xystoi", "xystos", "xystus", "yabber", "yabbie", "yachts", "yacked", "yaffed",
+    "yagers", "yahoos", "yairds", "yakked", "yakker", "yakuza", "zigged", "zigzag", "zillah", "zinced", "zincic",
+    "zincky", "zinebs", "zinged", "zinger", "zinnia", "zipped", "zipper", "zirams", "zircon" };
+  cimg::srand();
+  const char *const captcha_text = predef_words[std::rand()%(sizeof(predef_words)/sizeof(char*))];
+
+  // Create captcha image
+  //----------------------
+
+  // Write colored and distorted text
+  CImg<unsigned char> captcha(256,64,1,3,0), color(3);
+  char letter[2] = { 0 };
+  for (unsigned int k = 0; k<6; ++k) {
+    CImg<unsigned char> tmp;
+    *letter = captcha_text[k];
+    if (*letter) {
+      cimg_forX(color,i) color[i] = (unsigned char)(128 + (std::rand()%127));
+      tmp.draw_text((int)(2 + 8*cimg::rand()),
+                    (int)(12*cimg::rand()),
+                    letter,color.data(),0,1,std::rand()%2?38:57).resize(-100,-100,1,3);
+      const unsigned int dir = std::rand()%4, wph = tmp.width() + tmp.height();
+      cimg_forXYC(tmp,x,y,v) {
+        const int val = dir==0?x + y:(dir==1?x + tmp.height() - y:(dir==2?y + tmp.width() - x:
+                                                                   tmp.width() - x + tmp.height() - y));
+        tmp(x,y,v) = (unsigned char)std::max(0.0f,std::min(255.0f,1.5f*tmp(x,y,v)*val/wph));
+      }
+      if (std::rand()%2) tmp = (tmp.get_dilate(3)-=tmp);
+      tmp.blur((float)cimg::rand()*0.8f).normalize(0,255);
+      const float sin_offset = (float)cimg::rand(-1,1)*3, sin_freq = (float)cimg::rand(-1,1)/7;
+      cimg_forYC(captcha,y,v) captcha.get_shared_row(y,0,v).shift((int)(4*std::cos(y*sin_freq + sin_offset)));
+      captcha.draw_image(6 + 40*k,tmp);
+    }
+  }
+
+  // Add geometric and random noise
+  CImg<unsigned char> copy = (+captcha).fill(0);
+  for (unsigned int l = 0; l<3; ++l) {
+    if (l) copy.blur(0.5f).normalize(0,148);
+    for (unsigned int k = 0; k<10; ++k) {
+      cimg_forX(color,i) color[i] = (unsigned char)(128 + cimg::rand()*127);
+      if (cimg::rand()<0.5f) copy.draw_circle((int)(cimg::rand()*captcha.width()),
+                                              (int)(cimg::rand()*captcha.height()),
+                                              (int)(cimg::rand()*30),
+                                              color.data(),0.6f,~0U);
+      else copy.draw_line((int)(cimg::rand()*captcha.width()),
+                          (int)(cimg::rand()*captcha.height()),
+                          (int)(cimg::rand()*captcha.width()),
+                          (int)(cimg::rand()*captcha.height()),
+                          color.data(),0.6f);
+    }
+  }
+  captcha|=copy;
+  captcha.noise(10,2);
+
+  if (add_border)
+    captcha.draw_rectangle(0,0,captcha.width() - 1,captcha.height() - 1,
+                           CImg<unsigned char>::vector(255,255,255).data(),1.0f,~0U);
+  captcha = (+captcha).fill(255) - captcha;
+
+  // Write output image and captcha text
+  //-------------------------------------
+  std::printf("%s\n",captcha_text);
+  if (file_o) captcha.save(file_o);
+  else if (visu) {
+    CImgDisplay disp(CImg<unsigned char>(512,128,1,3,180).draw_image(128,32,captcha),captcha_text,0);
+    while (!disp.is_closed() && !disp.key()) { disp.wait(); if (disp.is_resized()) disp.resize(disp).wait(100); }
+  }
+  return 0;
+}