537 lines
17 KiB
Text
537 lines
17 KiB
Text
/*
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This is a Optical-Character-Recognition program
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Copyright (C) 2000-2006 Joerg Schulenburg
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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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 General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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Joerg.Schulenburg@physik.uni-magdeburg.de */
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/* Filter by tree, filter by number methods added by
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* William Webber, william@williamwebber.com. */
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#include "pgm2asc.h"
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#include <assert.h>
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#include <string.h>
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/*
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* Defining this causes assert() calls to be turned off runtime.
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*
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* This is normally taken care of by make.
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*/
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/* #define NDEBUG */
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// ------------------ (&~7)-pixmap-functions ------------------------
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/* test if pixel marked?
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* Returns: 0 if not marked, least 3 bits if marked.
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*/
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int marked (pix * p, int x, int y) {
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if (x < 0 || y < 0 || x >= p->x || y >= p->y)
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return 0;
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return (pixel_atp(p, x, y) & 7);
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}
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#define Nfilt3 6 /* number of 3x3 filter */
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/*
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* Filters to correct possible scanning or image errors.
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*
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* Each of these filters represents a 3x3 pixel area.
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* 0 represents a white or background pixel, 1 a black or
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* foreground pixel, and 2 represents a pixel of either value.
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* Note that this differs from the meaning of pixel values in
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* the image, where a high value means "white" (background),
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* and a low value means "black" (foreground).
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*
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* These filters are applied to the 3x3 environment of a pixel
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* to be retrieved from the image, centered around that pixel
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* (that is, the to-be-retrieved pixel corresponds with the
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* the fifth position of the filter).
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* If the filter matches that pixel environment, then
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* the returned value of the pixel is inverted (black->white
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* or white->black).
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*
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* So, for instance, the second filter below matches this
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* pattern:
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*
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* 000
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* X0X
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* 000
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*
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* and "fills in" the middle (retrieved) pixel to rejoin a line
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* that may have been broken by a scanning or image error.
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*/
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const char filt3[Nfilt3][9]={
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{0,0,0, 0,0,1, 1,0,0}, /* (-1,-1) (0,-1) (1,-1) (-1,0) (0,0) ... */
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{0,0,0, 1,0,1, 0,0,0},
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{1,0,0, 0,0,1, 0,0,0},
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{1,1,0, 0,1,0, 2,1,1},
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{0,0,1, 0,0,0, 2,1,0},
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{0,1,0, 0,0,0, 1,2,0}
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};
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/* 2=ignore_pixel, 0=white_background, 1=black_pixel */
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/*
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* Filter by matrix uses the above matrix of filters directly. Pixel
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* environments to be filtered are compared pixel by pixel against
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* these filters.
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*
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* Filter by number converts these filters into integer representations
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* and stores them in a table. Pixel environments are similarly
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* converted to integers, and looked up in the table.
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*
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* Filter by tree converts these filters into a binary tree. Pixel
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* environments are matched by traversing the tree.
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*
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* A typical performance ratio for these three methods is 20:9:7
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* respectively (i.e., the tree method takes around 35% of the
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* time of the matrix method).
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*/
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#define FILTER_BY_MATRIX 0
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#define FILTER_BY_NUMBER 1
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#define FILTER_BY_TREE 2
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#define FILTER_METHOD FILTER_BY_TREE
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/*
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* Defining FILTER_CHECKED causes filter results from either the tree
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* or the number method to be checked against results of the other
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* two methods to ensure correctness. This is for bug checking purposes
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* only.
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*/
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/* #define FILTER_CHECKED */
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/*
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* Defining FILTER_STATISTICS causes statistics to be kept on how many
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* times the filters are tried, how many times a filter matches, and
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* of these matches how many flip a black pixel to white, and how many
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* the reverse. These statistics are printed to stderr at the end of
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* the program run. Currently, statistics are only kept if the tree
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* filter method is being used.
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*/
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/* #define FILTER_STATISTICS */
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#ifdef FILTER_STATISTICS
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static int filter_tries = 0;
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static int filter_matches = 0;
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static int filter_blackened = 0;
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static int filter_whitened = 0;
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#endif
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#ifdef FILTER_STATISTICS
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void print_filter_stats() {
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fprintf(stderr, "\n# Error filter statistics: tries %d, matches %d, "
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"blackened %d, whitened %d\n",
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filter_tries, filter_matches, filter_blackened, filter_whitened);
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}
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#endif
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#if FILTER_METHOD == FILTER_BY_MATRIX || defined(FILTER_CHECKED)
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/*
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* Filter the pixel at (x,y) by directly applying the matrix.
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*/
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int pixel_filter_by_matrix(pix * p, int x, int y) {
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int i;
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static char c33[9];
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memset(c33, 0, sizeof(c33));
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/* copy environment of a point (only highest bit)
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bbg: FASTER now. It has 4 ifs less at least, 8 at most. */
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if (x > 0) { c33[3] = pixel_atp(p,x-1, y )>>7;
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if (y > 0) c33[0] = pixel_atp(p,x-1,y-1)>>7;
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if (y+1 < p->y) c33[6] = pixel_atp(p,x-1,y+1)>>7;
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}
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if (x+1 < p->x) { c33[5] = pixel_atp(p,x+1, y )>>7;
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if (y > 0) c33[2] = pixel_atp(p,x+1,y-1)>>7;
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if (y+1 < p->y) c33[8] = pixel_atp(p,x+1,y+1)>>7;
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}
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if (y > 0) c33[1] = pixel_atp(p, x ,y-1)>>7;
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c33[4] = pixel_atp(p, x , y )>>7;
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if (y+1 < p->y) c33[7] = pixel_atp(p, x ,y+1)>>7;
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/* do filtering */
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for (i = 0; i < Nfilt3; i++)
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if( ( (filt3[i][0]>>1) || c33[0]!=(1 & filt3[i][0]) )
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&& ( (filt3[i][1]>>1) || c33[1]!=(1 & filt3[i][1]) )
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&& ( (filt3[i][2]>>1) || c33[2]!=(1 & filt3[i][2]) )
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&& ( (filt3[i][3]>>1) || c33[3]!=(1 & filt3[i][3]) )
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&& ( (filt3[i][4]>>1) || c33[4]!=(1 & filt3[i][4]) )
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&& ( (filt3[i][5]>>1) || c33[5]!=(1 & filt3[i][5]) )
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&& ( (filt3[i][6]>>1) || c33[6]!=(1 & filt3[i][6]) )
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&& ( (filt3[i][7]>>1) || c33[7]!=(1 & filt3[i][7]) )
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&& ( (filt3[i][8]>>1) || c33[8]!=(1 & filt3[i][8]) ) ) {
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return ((filt3[i][4])?JOB->cfg.cs:0);
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}
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return pixel_atp(p, x, y) & ~7;
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}
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#endif
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#if FILTER_METHOD == FILTER_BY_NUMBER || defined(FILTER_CHECKED)
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#define NUM_TABLE_SIZE 512 /* max value of 9-bit value */
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/*
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* Recursively generates entries in the number table for a matrix filter.
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*
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* gen_num_filt is the number representation of the matrix filter.
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* This generation is handled recursively because this is the easiest
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* way to handle 2 (either value) entries in the filter, which lead
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* to 2 distinct entries in the number table (one for each alternate
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* value).
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*/
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void rec_generate_number_table(char * num_table, const char * filter,
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int i, unsigned short gen_num_filt) {
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if (i == 9) {
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/* Invert the value of the number representation, to reflect the
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* fact that the "white" is 0 in the filter, 1 (high) in the image. */
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gen_num_filt = ~gen_num_filt;
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gen_num_filt &= 0x01ff;
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assert(gen_num_filt < NUM_TABLE_SIZE);
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num_table[gen_num_filt] = 1;
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} else {
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if (filter[i] == 0 || filter[i] == 2)
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rec_generate_number_table(num_table, filter, i + 1, gen_num_filt);
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if (filter[i] == 1 || filter[i] == 2) {
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gen_num_filt |= (1 << (8 - i));
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rec_generate_number_table(num_table, filter, i + 1, gen_num_filt);
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}
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}
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}
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/*
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* Filter the pixel at (x, y) using a number table.
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*
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* Each filter can be converted into a 9-bit representation, where
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* filters containing 2 (either value) pixels are converted into
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* a separate numerical representation for each pixel, where position
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* i in the filter corresponds to bit i in the number. Each resulting
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* numerical representation N is represented as a 1 value in the Nth
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* position of a lookup table. A pixel's environment is converted in
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* the same way to a numeric representation P, and that environment
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* matches a filter if num_table[P] == 1.
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*/
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int pixel_filter_by_number(pix * p, int x, int y) {
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unsigned short val = 0;
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static char num_table[NUM_TABLE_SIZE];
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static int num_table_generated = 0;
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if (!num_table_generated) {
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int f;
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memset(num_table, 0, sizeof(num_table));
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for (f = 0; f < Nfilt3; f++)
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rec_generate_number_table(num_table, filt3[f], 0, 0);
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num_table_generated = 1;
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}
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/* calculate a numeric value for the 3x3 square around the pixel. */
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if (x > 0) { val |= (pixel_atp(p,x-1, y )>>7) << (8 - 3);
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if (y > 0) val |= (pixel_atp(p,x-1,y-1)>>7) << (8 - 0);
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if (y+1 < p->y) val |= (pixel_atp(p,x-1,y+1)>>7) << (8 - 6);
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}
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if (x+1 < p->x) { val |= (pixel_atp(p,x+1, y )>>7) << (8 - 5);
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if (y > 0) val |= (pixel_atp(p,x+1,y-1)>>7) << (8 - 2);
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if (y+1 < p->y) val |= (pixel_atp(p,x+1,y+1)>>7) << (8 - 8);
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}
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if (y > 0) val |= (pixel_atp(p, x ,y-1)>>7) << (8 - 1);
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val |= (pixel_atp(p, x , y )>>7) << (8 - 4);
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if (y+1 < p->y) val |= (pixel_atp(p, x ,y+1)>>7) << (8 - 7);
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assert(val < NUM_TABLE_SIZE);
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if (num_table[val])
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return (val & (1 << 4)) ? 0 : JOB->cfg.cs;
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else
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return pixel_atp(p, x, y) & ~7;
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}
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#endif
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#if FILTER_METHOD == FILTER_BY_TREE || defined(FILTER_CHECKED)
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#define TREE_ARRAY_SIZE 1024
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/* 1+ number of nodes in a complete binary tree of height 10 */
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/*
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* Recursively generate a tree representation of a filter.
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*/
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void rec_generate_tree(char * tree, const char * filter, int i, int n) {
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assert(i >= 0 && i <= 9);
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assert(n < TREE_ARRAY_SIZE);
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if (i == 9) {
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if (filter[4] == 0)
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tree[n] = 2;
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else
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tree[n] = 1;
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return;
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}
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/* first iteration has n == -1, does not set any values of the tree,
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just to find whether to start to the left or the right */
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if (n != -1)
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tree[n] = 1;
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if (filter[i] == 0)
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rec_generate_tree(tree, filter, i + 1, n * 2 + 2);
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else if (filter[i] == 1)
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rec_generate_tree(tree, filter, i + 1, n * 2 + 3);
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else {
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rec_generate_tree(tree, filter, i + 1, n * 2 + 2);
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rec_generate_tree(tree, filter, i + 1, n * 2 + 3);
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}
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}
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/*
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* Filter the pixel at (x, y) using the tree method.
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*
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* Each filter is represented by a single branch of a binary
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* tree, except for filters contain "either value" entries, which
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* bifurcate at that point in the branch. Each white pixel in the filter
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* is a left branch in the tree, each black pixel a right branch. The
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* final node of a branch indicates whether this filter turns a white
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* pixel black, or a black one white.
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*
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* We match a pixel's environment against this tree by similarly
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* using the pixels in that environment to traverse the tree. If
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* we run out of nodes before getting to the end of a branch, then
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* the environment doesn't match against any of the filters represented
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* by the tree. Otherwise, we return the value specified by the
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* final node.
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*
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* Since the total tree size, even including missing nodes, is small
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* (2 ^ 10), we can use a standard array representation of a binary
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* tree, where for the node tree[n], the left child is tree[2n + 2],
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* and the right tree[2n + 3]. The only information we want
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* from a non-leaf node is whether it exists (that is, is part of
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* a filter-representing branch). We represent this with the value
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* 1 at the node's slot in the array, the contrary by 0. For the
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* leaf node, 0 again represents non-existence, 1 that the filter
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* represented by this branch turns a black pixel white, and 2 a
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* white pixel black.
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*/
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int pixel_filter_by_tree(pix * p, int x, int y) {
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static char tree[TREE_ARRAY_SIZE];
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static int tree_generated = 0;
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int n;
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int pixel_val = pixel_atp(p, x, y) & ~7;
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#ifdef FILTER_STATISTICS
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static int registered_filter_stats = 0;
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if (!registered_filter_stats) {
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atexit(print_filter_stats);
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registered_filter_stats = 1;
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}
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filter_tries++;
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#endif /* FILTER_STATISTICS */
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if (!tree_generated) {
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int f;
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memset(tree, 0, sizeof(tree));
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for (f = 0; f < Nfilt3; f++) {
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const char * filter = filt3[f];
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rec_generate_tree(tree, filter, 0, -1);
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}
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tree_generated = 1;
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}
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n = -1;
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/* Note that for the image, low is black, high is white, whereas
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* for the filter, 0 is white, 1 is black. For the image, then,
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* high (white) means go left, low (black) means go right. */
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#define IS_BLACK(_dx,_dy) !(pixel_atp(p, x + (_dx), y + (_dy)) >> 7)
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#define IS_WHITE(_dx,_dy) (pixel_atp(p, x + (_dx), y + (_dy)) >> 7)
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#define GO_LEFT n = n * 2 + 2
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#define GO_RIGHT n = n * 2 + 3
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#define CHECK_NO_MATCH if (tree[n] == 0) return pixel_val
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/* Top row */
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if (y == 0) {
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/* top 3 pixels off edge == black == right
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n = 2 * (2 * (2 * -1 + 3) + 3) + 3 = 13 */
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n = 13;
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} else {
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if (x == 0 || IS_BLACK(-1, -1))
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GO_RIGHT;
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else
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GO_LEFT;
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if (IS_WHITE(0, -1))
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GO_LEFT;
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else
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GO_RIGHT;
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CHECK_NO_MATCH;
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if (x + 1 == p->x || IS_BLACK(+1, -1))
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GO_RIGHT;
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else
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GO_LEFT;
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CHECK_NO_MATCH;
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}
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/* Second row */
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if (x == 0 || IS_BLACK(-1, 0))
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GO_RIGHT;
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else
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GO_LEFT;
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CHECK_NO_MATCH;
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if (IS_WHITE(0, 0))
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GO_LEFT;
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else
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GO_RIGHT;
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CHECK_NO_MATCH;
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if (x + 1 == p->x || IS_BLACK(+1, 0))
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GO_RIGHT;
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else
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GO_LEFT;
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CHECK_NO_MATCH;
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/* bottom row */
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if (y + 1 == p->y) {
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/* bottom 3 pixels off edge == black == right
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n' = 2 * (2 * (2n + 3) + 3) + 3
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= 2 * (4n + 9) + 3
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= 8n + 21 */
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n = 8 * n + 21;
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} else {
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if (x == 0 || IS_BLACK(-1, +1))
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GO_RIGHT;
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else
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GO_LEFT;
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CHECK_NO_MATCH;
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if (IS_WHITE(0, 1))
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GO_LEFT;
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else
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GO_RIGHT;
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CHECK_NO_MATCH;
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if (x + 1 == p->x || IS_BLACK(+1, +1))
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GO_RIGHT;
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else
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GO_LEFT;
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}
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assert(n < TREE_ARRAY_SIZE);
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assert(tree[n] == 0 || tree[n] == 1 || tree[n] == 2);
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CHECK_NO_MATCH;
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#ifdef FILTER_STATISTICS
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filter_matches++;
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#endif
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if (tree[n] == 1) {
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#ifdef FILTER_STATISTICS
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if (pixel_atp(p, x, y) < JOB->cfg.cs)
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filter_whitened++;
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#endif
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return JOB->cfg.cs;
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} else {
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#ifdef FILTER_STATISTICS
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if (pixel_atp(p, x, y) >= JOB->cfg.cs)
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filter_blackened++;
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#endif
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return 0;
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}
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}
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#endif /* FILTER_METHOD == FILTER_BY_TREE */
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/*
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* This simple filter attempts to correct "fax"-like scan errors.
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*/
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int pixel_faxfilter(pix *p, int x, int y) {
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int r; // filter
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r = pixel_atp(p,x,y)&~7;
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/* {2,2,2, 2,0,1, 2,1,0} */
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if ((r&128) && (~pixel_atp(p,x+1, y )&128)
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&& (~pixel_atp(p, x ,y+1)&128)
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&& ( pixel_atp(p,x+1,y+1)&128))
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r = 64; /* faxfilter */
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else
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/* {2,2,2, 1,0,2, 0,1,2} */
|
|
if ((r&128) && (~pixel_atp(p,x-1, y )&128)
|
|
&& (~pixel_atp(p, x ,y+1)&128)
|
|
&& ( pixel_atp(p,x-1,y+1)&128))
|
|
r = 64; /* faxfilter */
|
|
return r & ~7;
|
|
}
|
|
|
|
#ifdef FILTER_CHECKED
|
|
/*
|
|
* Print out the 3x3 environment of a pixel as a 9-bit binary.
|
|
*
|
|
* For debugging purposes only.
|
|
*/
|
|
void print_pixel_env(FILE * out, pix * p, int x, int y) {
|
|
int x0, y0;
|
|
for (y0 = y - 1; y0 < y + 2; y0++) {
|
|
for (x0 = x - 1; x0 < x + 2; x0++) {
|
|
if (x0 < 0 || x0 >= p->x || y0 < 0 || y0 >= p->y)
|
|
fputc('?', out);
|
|
else if (pixel_atp(p, x0, y0) >> 7)
|
|
fputc('0', out);
|
|
else
|
|
fputc('1', out);
|
|
}
|
|
}
|
|
}
|
|
#endif
|
|
|
|
/* this function is heavily used
|
|
* test if pixel was set, remove low bits (marks) --- later with error-correction
|
|
* result depends on n_run, if n_run>0 filter are used
|
|
* Returns: pixel-color (without marks)
|
|
*/
|
|
int getpixel(pix *p, int x, int y){
|
|
if ( x < 0 || y < 0 || x >= p->x || y >= p->y )
|
|
return 255 & ~7;
|
|
|
|
/* filter will be used only once later, when vectorization replaces pixel
|
|
* processing
|
|
*/
|
|
if (JOB->tmp.n_run > 0) { /* use the filters (correction of errors) */
|
|
#if FILTER_METHOD == FILTER_BY_NUMBER
|
|
int pix = pixel_filter_by_number(p, x, y);
|
|
#ifdef FILTER_CHECKED
|
|
int pix2 = pixel_filter_by_matrix(p, x, y);
|
|
if (pix != pix2) {
|
|
fprintf(stderr,
|
|
"# BUG: pixel_filter: by number: %d; by matrix: %d, "
|
|
"by atp %d; env: ", pix, pix2, pixel_atp(p, x, y) & ~7);
|
|
print_pixel_env(stderr, p, x, y);
|
|
fputc('\n', stderr);
|
|
}
|
|
#endif /* FILTER_CHECKED */
|
|
return pix;
|
|
#elif FILTER_METHOD == FILTER_BY_MATRIX
|
|
return pixel_filter_by_matrix(p, x, y);
|
|
#elif FILTER_METHOD == FILTER_BY_TREE
|
|
int pix = pixel_filter_by_tree(p, x, y);
|
|
#ifdef FILTER_CHECKED
|
|
int pix2 = pixel_filter_by_matrix(p, x, y);
|
|
int pix3 = pixel_filter_by_number(p, x, y);
|
|
if (pix != pix2 || pix != pix3) {
|
|
fprintf(stderr,
|
|
"# BUG: pixel_filter: tree: %d; matrix: %d, "
|
|
"number: %d, atp %d; env: ", pix, pix2, pix3,
|
|
pixel_atp(p, x, y) & ~7);
|
|
print_pixel_env(stderr, p, x, y);
|
|
fputc('\n', stderr);
|
|
}
|
|
#endif /* FILTER_CHECKED */
|
|
return pix;
|
|
#else
|
|
#error FILTER_METHOD not defined
|
|
#endif /* FILTER_BY_NUMBER */
|
|
}
|
|
|
|
return (pixel_atp(p,x,y) & ~7);
|
|
}
|
|
|
|
/* modify pixel, test if out of range */
|
|
void put(pix * p, int x, int y, int ia, int io) {
|
|
if (x < p->x && x >= 0 && y >= 0 && y < p->y)
|
|
pixel_atp(p, x, y) = (pixel_atp(p, x, y) & ia) | io;
|
|
}
|