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Added OpenALPR library
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Matt Hill
372
src/openalpr/binarize_wolf.cpp
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372
src/openalpr/binarize_wolf.cpp
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/*
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* Copyright (c) 2013 New Designs Unlimited, LLC
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* Opensource Automated License Plate Recognition [http://www.openalpr.com]
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*
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* This file is part of OpenAlpr.
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*
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* OpenAlpr is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License
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* version 3 as published by the Free Software Foundation
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**************************************************************
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* Binarization with several methods
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* (0) Niblacks method
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* (1) Sauvola & Co.
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* ICDAR 1997, pp 147-152
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* (2) by myself - Christian Wolf
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* Research notebook 19.4.2001, page 129
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* (3) by myself - Christian Wolf
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* 20.4.2007
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*
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* See also:
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* Research notebook 24.4.2001, page 132 (Calculation of s)
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**************************************************************/
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#include "binarize_wolf.h"
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// *************************************************************
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// glide a window across the image and
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// create two maps: mean and standard deviation.
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// *************************************************************
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float calcLocalStats (Mat &im, Mat &map_m, Mat &map_s, int winx, int winy) {
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float m,s,max_s, sum, sum_sq, foo;
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int wxh = winx/2;
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int wyh = winy/2;
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int x_firstth= wxh;
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int y_lastth = im.rows-wyh-1;
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int y_firstth= wyh;
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float winarea = winx*winy;
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max_s = 0;
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for (int j = y_firstth ; j<=y_lastth; j++)
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{
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// Calculate the initial window at the beginning of the line
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sum = sum_sq = 0;
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for (int wy=0 ; wy<winy; wy++)
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for (int wx=0 ; wx<winx; wx++) {
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foo = im.uget(wx,j-wyh+wy);
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sum += foo;
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sum_sq += foo*foo;
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}
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m = sum / winarea;
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s = sqrt ((sum_sq - (sum*sum)/winarea)/winarea);
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if (s > max_s)
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max_s = s;
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map_m.fset(x_firstth, j, m);
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map_s.fset(x_firstth, j, s);
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// Shift the window, add and remove new/old values to the histogram
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for (int i=1 ; i <= im.cols-winx; i++) {
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// Remove the left old column and add the right new column
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for (int wy=0; wy<winy; ++wy) {
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foo = im.uget(i-1,j-wyh+wy);
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sum -= foo;
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sum_sq -= foo*foo;
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foo = im.uget(i+winx-1,j-wyh+wy);
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sum += foo;
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sum_sq += foo*foo;
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}
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m = sum / winarea;
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s = sqrt ((sum_sq - (sum*sum)/winarea)/winarea);
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if (s > max_s)
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max_s = s;
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map_m.fset(i+wxh, j, m);
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map_s.fset(i+wxh, j, s);
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}
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}
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return max_s;
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}
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/**********************************************************
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* The binarization routine
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**********************************************************/
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void NiblackSauvolaWolfJolion (Mat im, Mat output, NiblackVersion version,
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int winx, int winy, float k) {
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float dR = BINARIZEWOLF_DEFAULTDR;
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float m, s, max_s;
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float th=0;
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double min_I, max_I;
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int wxh = winx/2;
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int wyh = winy/2;
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int x_firstth= wxh;
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int x_lastth = im.cols-wxh-1;
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int y_lastth = im.rows-wyh-1;
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int y_firstth= wyh;
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int mx, my;
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// Create local statistics and store them in a float matrices
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Mat map_m = Mat::zeros (im.rows, im.cols, CV_32F);
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Mat map_s = Mat::zeros (im.rows, im.cols, CV_32F);
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max_s = calcLocalStats (im, map_m, map_s, winx, winy);
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minMaxLoc(im, &min_I, &max_I);
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Mat thsurf (im.rows, im.cols, CV_32F);
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// Create the threshold surface, including border processing
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// ----------------------------------------------------
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for (int j = y_firstth ; j<=y_lastth; j++) {
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// NORMAL, NON-BORDER AREA IN THE MIDDLE OF THE WINDOW:
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for (int i=0 ; i <= im.cols-winx; i++) {
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m = map_m.fget(i+wxh, j);
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s = map_s.fget(i+wxh, j);
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// Calculate the threshold
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switch (version) {
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case NIBLACK:
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th = m + k*s;
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break;
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case SAUVOLA:
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th = m * (1 + k*(s/dR-1));
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break;
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case WOLFJOLION:
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th = m + k * (s/max_s-1) * (m-min_I);
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break;
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default:
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cerr << "Unknown threshold type in ImageThresholder::surfaceNiblackImproved()\n";
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exit (1);
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}
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thsurf.fset(i+wxh,j,th);
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if (i==0) {
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// LEFT BORDER
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for (int i=0; i<=x_firstth; ++i)
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thsurf.fset(i,j,th);
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// LEFT-UPPER CORNER
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if (j==y_firstth)
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for (int u=0; u<y_firstth; ++u)
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for (int i=0; i<=x_firstth; ++i)
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thsurf.fset(i,u,th);
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// LEFT-LOWER CORNER
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if (j==y_lastth)
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for (int u=y_lastth+1; u<im.rows; ++u)
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for (int i=0; i<=x_firstth; ++i)
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thsurf.fset(i,u,th);
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}
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// UPPER BORDER
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if (j==y_firstth)
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for (int u=0; u<y_firstth; ++u)
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thsurf.fset(i+wxh,u,th);
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// LOWER BORDER
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if (j==y_lastth)
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for (int u=y_lastth+1; u<im.rows; ++u)
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thsurf.fset(i+wxh,u,th);
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}
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// RIGHT BORDER
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for (int i=x_lastth; i<im.cols; ++i)
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thsurf.fset(i,j,th);
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// RIGHT-UPPER CORNER
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if (j==y_firstth)
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for (int u=0; u<y_firstth; ++u)
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for (int i=x_lastth; i<im.cols; ++i)
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thsurf.fset(i,u,th);
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// RIGHT-LOWER CORNER
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if (j==y_lastth)
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for (int u=y_lastth+1; u<im.rows; ++u)
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for (int i=x_lastth; i<im.cols; ++i)
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thsurf.fset(i,u,th);
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}
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for (int y=0; y<im.rows; ++y)
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for (int x=0; x<im.cols; ++x)
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{
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if (im.uget(x,y) >= thsurf.fget(x,y))
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{
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output.uset(x,y,255);
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}
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else
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{
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output.uset(x,y,0);
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}
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}
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}
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/**********************************************************
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* The main function
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**********************************************************/
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/**********************************************************
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* Usage
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**********************************************************/
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/*
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static void usage (char *com) {
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cerr << "usage: " << com << " [ -x <winx> -y <winy> -k <parameter> ] [ version ] <inputimage> <outputimage>\n\n"
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<< "version: n Niblack (1986) needs white text on black background\n"
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<< " s Sauvola et al. (1997) needs black text on white background\n"
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<< " w Wolf et al. (2001) needs black text on white background\n"
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<< "\n"
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<< "Default version: w (Wolf et al. 2001)\n"
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<< "\n"
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<< "example:\n"
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<< " " << com << " w in.pgm out.pgm\n"
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<< " " << com << " in.pgm out.pgm\n"
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<< " " << com << " s -x 50 -y 50 -k 0.6 in.pgm out.pgm\n";
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}
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int main (int argc, char **argv)
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{
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char version;
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int c;
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int winx=0, winy=0;
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float optK=0.5;
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bool didSpecifyK=false;
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NiblackVersion versionCode;
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char *inputname, *outputname, *versionstring;
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cerr << "===========================================================\n"
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<< "Christian Wolf, LIRIS Laboratory, Lyon, France.\n"
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<< "christian.wolf@liris.cnrs.fr\n"
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<< "Version " << BINARIZEWOLF_VERSION << endl
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<< "===========================================================\n";
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// Argument processing
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while ((c = getopt (argc, argv, "x:y:k:")) != EOF) {
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switch (c) {
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case 'x':
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winx = atof(optarg);
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break;
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case 'y':
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winy = atof(optarg);
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break;
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case 'k':
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optK = atof(optarg);
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didSpecifyK = true;
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break;
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case '?':
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usage (*argv);
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cerr << "\nProblem parsing the options!\n\n";
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exit (1);
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}
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}
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switch(argc-optind)
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{
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case 3:
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versionstring=argv[optind];
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inputname=argv[optind+1];
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outputname=argv[optind+2];
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break;
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case 2:
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versionstring=(char *) "w";
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inputname=argv[optind];
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outputname=argv[optind+1];
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break;
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default:
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usage (*argv);
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exit (1);
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}
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cerr << "Adaptive binarization\n"
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<< "Threshold calculation: ";
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// Determine the method
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version = versionstring[0];
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switch (version)
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{
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case 'n':
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versionCode = NIBLACK;
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cerr << "Niblack (1986)\n";
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break;
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case 's':
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versionCode = SAUVOLA;
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cerr << "Sauvola et al. (1997)\n";
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break;
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case 'w':
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versionCode = WOLFJOLION;
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cerr << "Wolf and Jolion (2001)\n";
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break;
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default:
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usage (*argv);
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cerr << "\nInvalid version: '" << version << "'!";
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}
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cerr << "parameter k=" << optK << endl;
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if (!didSpecifyK)
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cerr << "Setting k to default value " << optK << endl;
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// Load the image in grayscale mode
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Mat input = imread(inputname,CV_LOAD_IMAGE_GRAYSCALE);
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if ((input.rows<=0) || (input.cols<=0)) {
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cerr << "*** ERROR: Couldn't read input image " << inputname << endl;
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exit(1);
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}
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// Treat the window size
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if (winx==0||winy==0) {
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cerr << "Input size: " << input.cols << "x" << input.rows << endl;
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winy = (int) (2.0 * input.rows-1)/3;
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winx = (int) input.cols-1 < winy ? input.cols-1 : winy;
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// if the window is too big, than we asume that the image
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// is not a single text box, but a document page: set
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// the window size to a fixed constant.
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if (winx > 100)
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winx = winy = 40;
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cerr << "Setting window size to [" << winx
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<< "," << winy << "].\n";
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}
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// Threshold
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Mat output (input.rows, input.cols, CV_8U);
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NiblackSauvolaWolfJolion (input, output, versionCode, winx, winy, optK);
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// Write the tresholded file
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cerr << "Writing binarized image to file '" << outputname << "'.\n";
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imwrite (outputname, output);
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return 0;
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}
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*/
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