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/* thin-image.c: thin binary image
Copyright (C) 2001, 2002 Martin Weber
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License
as published by the Free Software Foundation; either version 2.1 of
the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA. */
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "mallocvar.h"
#include "thin-image.h"
#include "logreport.h"
#include "message.h"
#include "bitmap.h"
#define PIXEL_SET(p, new) ((void)memcpy((p), (new), sizeof(Pixel)))
#define PIXEL_EQUAL(p1, p2) \
((p1)[0] == (p2)[0] && (p1)[1] == (p2)[1] && (p1)[2] == (p2)[2])
typedef unsigned char Pixel[3]; /* RGB pixel data type */
void thin3(bitmap_type *image, Pixel colour);
void thin1(bitmap_type *image, unsigned char colour);
/* -------------------------------- ThinImage - Thin binary image. --------------------------- *
*
* Description:
* Thins the supplied binary image using Rosenfeld's parallel
* thinning algorithm.
*
* On Entry:
* image = Image to thin.
*
* -------------------------------------------------------------------------------------------- */
/* Direction masks: */
/* N S W E */
static unsigned int masks[] = { 0200, 0002, 0040, 0010 };
/* True if pixel neighbor map indicates the pixel is 8-simple and */
/* not an end point and thus can be deleted. The neighborhood */
/* map is defined as an integer of bits abcdefghi with a non-zero */
/* bit representing a non-zero pixel. The bit assignment for the */
/* neighborhood is: */
/* */
/* a b c */
/* d e f */
/* g h i */
static unsigned char todelete[512] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
static pixel background;
void
thin_image(bitmap_type *image, bool bgSpec, pixel bg,
at_exception_type * exp)
{
/* This is nasty as we need to call thin once for each
* colour in the image the way I do this is to keep a second
* copy of the bitmap and to use this to keep
* track of which colours have not yet been processed,
* trades time for pathological case memory.....*/
long m, n, num_pixels;
bitmap_type bm;
unsigned int const spp = image->np;
unsigned int const width = image->width;
unsigned int const height = image->height;
if (bgSpec)
background = bg;
else
PPM_ASSIGN(background, 255, 255, 255);
/* Clone the image */
bm.height = image->height;
bm.width = image->width;
bm.np = image->np;
MALLOCARRAY(bm.bitmap, height * width * spp);
if (bm.bitmap == NULL)
pm_error("Unable to get memory for thin image bitmap clone");
memcpy(bm.bitmap, image->bitmap, height * width * spp);
num_pixels = height * width;
switch (spp)
{
case 3:
{
Pixel *ptr = (Pixel*)bm.bitmap;
Pixel bg_color;
bg_color[0] = PPM_GETR(background);
bg_color[1] = PPM_GETG(background);
bg_color[2] = PPM_GETB(background);
for (n = num_pixels - 1; n >= 0L; --n)
{
Pixel p;
PIXEL_SET(p, ptr[n]);
if (!PIXEL_EQUAL(p, bg_color))
{
/* we have a new colour in the image */
LOG3("Thinning colour (%x, %x, %x)\n", p[0], p[1], p[2]);
for (m = n - 1; m >= 0L; --m)
{
if (PIXEL_EQUAL(ptr[m], p))
PIXEL_SET(ptr[m], bg_color);
}
thin3(image, p);
}
}
break;
}
case 1:
{
unsigned char * const ptr = bm.bitmap;
unsigned char bg_color;
if (PPM_ISGRAY(background))
bg_color = PPM_GETR(background);
else
bg_color = ppm_luminosity(background);
for (n = num_pixels - 1; n >= 0L; --n)
{
unsigned char c = ptr[n];
if (c != bg_color)
{
LOG1 ("Thinning colour %x\n", c);
for (m = n - 1; m >= 0L; --m)
if (ptr[m] == c) ptr[m] = bg_color;
thin1(image, c);
}
}
break;
}
default:
{
LOG1 ("thin_image: Don't know how to interpret %u-plane images", spp);
at_exception_fatal(exp, "thin_image: wrong plane images are passed");
goto cleanup;
}
}
cleanup:
free (bm.bitmap);
}
void thin3(bitmap_type *image, Pixel colour)
{
Pixel *ptr, *y_ptr, *y1_ptr;
Pixel bg_color;
unsigned int xsize, ysize; /* Image resolution */
unsigned int x, y; /* Pixel location */
unsigned int i; /* Pass index */
unsigned int pc = 0; /* Pass count */
unsigned int count = 1; /* Deleted pixel count */
unsigned int p, q; /* Neighborhood maps of adjacent*/
/* cells */
unsigned char *qb; /* Neighborhood maps of previous*/
/* scanline */
unsigned int m; /* Deletion direction mask */
bg_color[0] = PPM_GETR(background);
bg_color[1] = PPM_GETG(background);
bg_color[2] = PPM_GETB(background);
LOG (" Thinning image.....\n ");
xsize = image->width;
ysize = image->height;
MALLOCARRAY_NOFAIL(qb, xsize);
qb[xsize-1] = 0; /* Used for lower-right pixel */
ptr = (Pixel*)image->bitmap;
while ( count ) { /* Scan image while deletions */
pc++;
count = 0;
for ( i = 0 ; i < 4 ; i++ ) {
m = masks[i];
/* Build initial previous scan buffer. */
p = PIXEL_EQUAL(ptr[0], colour);
for ( x = 0 ; x < xsize-1 ; x++ )
qb[x] = (unsigned char) (p = ((p<<1)&0006) | (unsigned int) PIXEL_EQUAL(ptr[x+1],
colour));
/* Scan image for pixel deletion candidates. */
y_ptr = ptr; y1_ptr = ptr + xsize;
for (y = 0; y < ysize - 1; y++, y_ptr += xsize, y1_ptr += xsize)
{
q = qb[0];
p = ((q<<2)&0330) | (unsigned int) PIXEL_EQUAL(y1_ptr[0], colour);
for ( x = 0 ; x < xsize-1 ; x++ ) {
q = qb[x];
p = ((p<<1)&0666) | ((q<<3)&0110) |
(unsigned int) PIXEL_EQUAL(y1_ptr[x+1], colour);
qb[x] = (unsigned char) p;
if ((i != 2 || x != 0) && ((p&m) == 0) && todelete[p] ) {
count++; /* delete the pixel */
PIXEL_SET(y_ptr[x], bg_color);
}
}
/* Process right edge pixel. */
p = (p<<1)&0666;
if (i != 3 && (p&m) == 0 && todelete[p] ) {
count++;
PIXEL_SET(y_ptr[xsize-1], bg_color);
}
}
if (i != 1)
{
/* Process bottom scan line. */
q = qb[0];
p = ((q<<2)&0330);
y_ptr = ptr + xsize * (ysize - 1);
for ( x = 0 ; x < xsize ; x++ ) {
q = qb[x];
p = ((p<<1)&0666) | ((q<<3)&0110);
if ((i != 2 || x != 0) && (p&m) == 0 && todelete[p]) {
count++;
PIXEL_SET(y_ptr[x], bg_color);
}
}
}
}
LOG2 ("ThinImage: pass %d, %d pixels deleted\n", pc, count);
}
free (qb);
}
void thin1(bitmap_type *image, unsigned char colour)
{
unsigned char *ptr, *y_ptr, *y1_ptr;
unsigned char bg_color;
unsigned int xsize, ysize; /* Image resolution */
unsigned int x, y; /* Pixel location */
unsigned int i; /* Pass index */
unsigned int pc = 0; /* Pass count */
unsigned int count = 1; /* Deleted pixel count */
unsigned int p, q; /* Neighborhood maps of adjacent*/
/* cells */
unsigned char *qb; /* Neighborhood maps of previous*/
/* scanline */
unsigned int m; /* Deletion direction mask */
if (PPM_ISGRAY(background))
bg_color = PPM_GETR(background);
else
bg_color = ppm_luminosity(background);
LOG (" Thinning image.....\n ");
xsize = image->width;
ysize = image->height;
MALLOCARRAY_NOFAIL(qb, xsize);
qb[xsize-1] = 0; /* Used for lower-right pixel */
ptr = image->bitmap;
while ( count ) { /* Scan image while deletions */
pc++;
count = 0;
for ( i = 0 ; i < 4 ; i++ ) {
m = masks[i];
/* Build initial previous scan buffer. */
p = (ptr[0] == colour);
for ( x = 0 ; x < xsize-1 ; x++ )
qb[x] = (unsigned char) (p = ((p<<1)&0006) | (unsigned int)(ptr[x+1] == colour));
/* Scan image for pixel deletion candidates. */
y_ptr = ptr; y1_ptr = ptr + xsize;
for (y = 0; y < ysize - 1; y++, y_ptr += xsize, y1_ptr += xsize)
{
q = qb[0];
p = ((q<<2)&0330) | (y1_ptr[0] == colour);
for ( x = 0 ; x < xsize-1 ; x++ ) {
q = qb[x];
p = ((p<<1)&0666) | ((q<<3)&0110) | (unsigned int) (y1_ptr[x+1]==colour);
qb[x] = (unsigned char) p;
if ( ((p&m) == 0) && todelete[p] ) {
count++;
y_ptr[x] = bg_color; /* delete the pixel */
}
}
/* Process right edge pixel. */
p = (p<<1)&0666;
if ( (p&m) == 0 && todelete[p] ) {
count++;
y_ptr[xsize-1] = bg_color;
}
}
/* Process bottom scan line. */
q = qb[0];
p = ((q<<2)&0330);
y_ptr = ptr + xsize * (ysize - 1);
for ( x = 0 ; x < xsize ; x++ ) {
q = qb[x];
p = ((p<<1)&0666) | ((q<<3)&0110);
if ( (p&m) == 0 && todelete[p] ) {
count++;
y_ptr[x] = bg_color;
}
}
}
LOG2("thin1: pass %d, %d pixels deleted\n", pc, count);
}
free (qb);
}
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