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The C Users' Group Library 1994 August
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wc-cdrom-cusersgrouplibrary-1994-08.iso
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v_11_08
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1993-05-05
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/***************************************************************
* file: ZONE.C
* purpose: text region detection via cellular automata
**************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "zone.h"
/* local data */
static ZONE zone_list[MAX_ZONES]; /* this could be dynamically allocated */
static int zone_count;
/* local prototypes */
static unsigned char *sample_page(int *dx,int *dy,int *samplex,int *sampley);
static void cut_vertical_lines(unsigned char *image,int dx,int dy);
static void block_zones(unsigned char *image,int dx,int dy,int coarseness);
static void sequence_zones(unsigned char *image,int dx,int dy,int order);
static int extract_zone(unsigned char *image,int dx,int dy,int x,int y,ZONE *zone_ptr);
static void overlap_zones(ZONE *zone_array,int *array_size);
/************************************************
* function: int zone(int coarseness)
* The process steps are:
* 1) Sample the page
* 2) Cut vertical lines from the page
* 3) Block out zones via cellular automata
* 4) Extract the zones
* 5) Sequence zones
* parameters: coarseness value 0-5, order (COLUMN or ROW)
* returns: 1 if OK or 0 if error, see errno
************************************************/
int zone(int coarseness,int order)
{
unsigned char *image;
int dx,dy;
int samplex,sampley;
int i;
if (coarseness < 0 || coarseness > 5)
{ /* test coarseness parameter */
errno = EINVAL;
return 0;
}
/* get a scaled copy of the page */
image = sample_page(&dx,&dy,&samplex,&sampley);
if (image == NULL) /* memory? */
return 0;
#if CUT_VERTICAL_LINES
cut_vertical_lines(image,dx,dy); /* remove boxes around text */
#endif
block_zones(image,dx,dy,coarseness); /* block out zones */
sequence_zones(image,dx,dy,order);
for (i = 0 ; i < zone_count ; i++)
{ /* translate to full page */
zone_list[i].x1 *= samplex;
zone_list[i].y1 *= sampley;
zone_list[i].x2 *= samplex;
zone_list[i].y2 *= sampley;
}
free(image); /* clean up */
return 1;
}
/**************** LOCAL FUNCTIONS ****************/
/************************************************
* function: static unsigned char *sample_page(int *dx,int *dy,int *samplex,int *sampley)
* Sample the page. Normally, the entire page is stored in memory. Since
* the memory requirements are typically a megabyte, the page, in DOS
* machines, is somewhere in extended memory. So that this demo can
* work on machines lacking extended memory, I sampled the page when I
* scaled it for display. See display_sample() below. However, I
* have #ifed around the code that is normally used to sample the page
* from the memory image. You need to provide two functions, as well as
* the extended memory handler. They are void memory_info(DISPLAY_BOX *);
* which gets the x/y extents of the image, and (unsigned char *
* memory_ptr(int y); which returns a pointer to a scan line in the memory
* image. Sample_page() creates a standardized, reduced image suitable for
* cellular automation. The sample has each byte, not bit, representing a
* pixel area. The byte is 0xff if black or 0x00 if white.
* The sampling procedure is important for region finding. If possible
* it should be a function of the density of the original image. If
* the image isn't square, for example a 200x100 fax file, then the
* x and y sampling should be adjusted accordingly. Since I don't
* have dpi information here, I am scaling it to a typical, 200dpi,
* value after it was adjusted for screen display.
* Note: Bit 7 is leftmost and 0 is rightmost; 1 bits are black, 0 are white.
* parameters: pointers to storage for the byte width and height of the sampled
* image and the sample bit distance in x and y
* returns: pointer to sampled page or NULL if no memory
************************************************/
static unsigned char *sample_page(int *dx,int *dy,int *samplex,int *sampley)
{
static unsigned char bit_mask[] = {0x80,0x40,0x20,0x10,0x08,0x04,0x02,0x01};
unsigned char *image,*line_ptr,*line_ptr2,*buff_ptr;
DISPLAY_BOX file;
unsigned int x,y,width,height;
memory_info(&file); /* need to provide this, gets file dimensions */
/* from memory image of file */
*samplex = SAMPLE_200_X; /* sample sizes */
*sampley = SAMPLE_200_Y;
*dx = file.width / *samplex; /* extent of sample */
*dy = file.height / *sampley;
while (((long)*dx * (long)*dy) > MAX_MALLOC)
{ /* adjust sampling to fit memory restrictions */
(*samplex)++;
(*sampley)++;
*dx = file.width / *samplex;
*dy = file.height / *sampley;
}
if ((image = malloc(*dx * *dy)) == NULL) /* allocate sample buffer */
return NULL;
memset(image,WHITE,*dx * *dy); /* set to white */
width = *dx * *samplex;
height = *dy * *sampley;
if (*samplex >= 8)
{ /* byte sampling */
for (y = 0, buff_ptr = image ; y < height ; y += *sampley)
{ /* for each y sample */
/* need to provide memory_ptr which gets a pointer
* to a scan line from the memory image of the file */
line_ptr = memory_ptr(y);
line_ptr2 = memory_ptr(y + *sampley/2); /* double sample in y */
for (x = 0 ; x < width ; x += *samplex, buff_ptr++)
if (*(line_ptr+(x>>3)) | *(line_ptr2+(x>>3)))
*buff_ptr = BLACK; /* if byte has black, set sample */
}
}
else
{ /* bit sampling */
for (y = 0, buff_ptr = image ; y < height ; y += *sampley)
{ /* for each y sample */
/* need to provide memory_ptr which gets a pointer
* to a scan line from the memory image of the file */
line_ptr = memory_ptr(y);
line_ptr2 = memory_ptr(y + *sampley/2); /* double sample in y */
for (x = 0 ; x < width ; x += *samplex, buff_ptr++)
if ((*(line_ptr+(x>>3)) | *(line_ptr2+(x>>3))) & bit_mask[x&7])
*buff_ptr = BLACK; /* if bit is black, set sample */
}
}
return image;
}
#if CUT_VERTICAL_LINES
/************************************************
* function: static void cut_vertical_lines(unsigned char *image,int dx,int dy)
* Remove vertical lines from sample. The purpose of this function is to
* unbox text. Removing the vertical box lines accomplishes this. Trying
* to remove the horizontal lines is dangerous because you might also remove
* the text.
* parameters: pointer to sampled image buffer and x/y extents of buffer
* returns: nothing
************************************************/
static void cut_vertical_lines(unsigned char *image,int dx,int dy)
{
int x,y,count,y1;
unsigned char *ptr,*qtr;
for (x = 0 ; x < dx ; x++) /* scan image left to right */
{
ptr = image+x;
count = 0;
for (y = 0 ; y < dy ; y++, ptr += dx)
{ /* scan up and down counting line pixels */
if (*ptr)
count++;
else
count = 0;
if (count >= VERTICAL_LINE_SIZE)
{ /* we have a veritcal line */
for (y1=y, qtr=ptr ; *ptr!=WHITE && y>=0 ; y--, ptr-=dx)
*ptr = WHITE; /* white out moving up */
for (y=y1+1, ptr=qtr+dx ; *ptr!=WHITE && y<dy ; ptr+=dx)
*ptr = WHITE; /* white out moving down */
count = 0; /* reset counter */
}
}
}
}
#endif
/************************************************
* function: static void block_zones(unsigned char *image,int dx,int dy,int coarseness)
* Use cellular automata to create blocks from image. Each block represents
* a region of text. There are two steps to the process. First, use cellular
* automata to sketch the reason. Second, use the coarseness (0-5) to coalesce
* the regions. A higher coarseness value will make larger zones.
* parameters: pointer to image buffer, x/y extents of buffer and coarseness
* of zoning (0-5)
* returns: nothing
************************************************/
static void block_zones(unsigned char *image,int dx,int dy,int coarseness)
{
int i,j,x,y,score;
unsigned char *line,*pixel;
for (y=1, line=image+dx ; y < dy-1 ; y++, line+=dx)
{ /* walk through buffer scanning for neighbors */
for (x=1, pixel=line+1 ; x < dx-1 ; x++, pixel++)
{
score = 0;
if (*(pixel-1) & ALIVE) /* left */
score++;
if (*(pixel+1) & ALIVE) /* right */
score++;
if (*(pixel-dx) & ALIVE) /* up */
score++;
if (*(pixel+dx) & ALIVE) /* down */
score++;
if (*pixel == WHITE && score >= LIFE_SCORE)
*pixel = PREGNANT;
else if (*pixel == BLACK && score <= DEATH_SCORE)
*pixel = SICK;
}
}
for (pixel = image ; pixel < image + dy * dx ; pixel++)
{ /* birth and bury */
if (*pixel == PREGNANT)
*pixel = BLACK;
else if (*pixel == SICK)
*pixel = WHITE;
}
if (coarseness <= 0) /* no need to coalesce */
return;
/* coalesce regions, based on coarseness, i.e. coarseness == 2
* will close all horizontal/vertical gaps of 2 pixels */
for (y=0, line=image+1 ; y < dy ; y++, line+=dx)
{ /* coalesce horizontally */
for (x=1, pixel=line ; x < dx-coarseness ; x++, pixel++)
{
if (*pixel == WHITE && *(pixel-1) == BLACK)
{
for (i = 1 ; i <= coarseness ; i++)
{
if (*(pixel+i))
{
for (i = 0 ; i < coarseness ; i++, pixel++)
*pixel = BLACK;
pixel--;
x += coarseness-1;
break;
}
}
}
}
}
for (x=0, line=image+dx ; x < dx ; x++, line++)
{ /* coalesce vertically */
for (y=1, pixel=line ; y < dy-coarseness ; y++, pixel+=dx)
{
if (*pixel == WHITE && *(pixel-dx) == BLACK)
{
for (i=1, j=dx ; i <= coarseness ; i++, j+=dx)
{
if (*(pixel+j))
{
for (i = 0 ; i < coarseness ; i++, pixel+=dx)
*pixel = BLACK;
pixel -= dx;
y += (coarseness-1);
break;
}
}
}
}
}
}
/************************************************
* function: static void sequence_zones(unsigned char *image,int dx,int dy,int order)
* Extract zones from buffer, place in zone_list, update zone_count and
* sequence zones so they are in either COLUMN_MAJOR or ROW_MAJOR reading order.
* parameters: pointer to image buffer and x/y extents of image in buffer
* order, COLUMN_MAJOR or ROW_MAJOR
* returns: nothing
************************************************/
static void sequence_zones(unsigned char *image,int dx,int dy,int order)
{
int x,y,i,j,index,fudge_x,fudge_y;
unsigned char *ptr;
ZONE temp;
for (y=0, zone_count=0 ; y < dy && zone_count < MAX_ZONES ; y+=MIN_Y_ZONE)
{ /* extract zones from block images in y order */
ptr = image + y * dx;
for (x = 0 ; x < dx ; x += MIN_X_ZONE)
if (*(ptr+x)) /* found point */
{
if (zone_count >= MAX_ZONES)
break;
while (x > 0 && *(ptr+x-1)) /* back up to left side */
x--;
if (extract_zone(image,dx,dy,x,y,zone_list+zone_count))
zone_count++; /* get zone */
}
}
if (zone_count == 0)
{ /* if no zones, make the entire page one big zone */
zone_list[0].x1 = zone_list[0].y1 = 0;
zone_list[0].x2 = dx-1;
zone_list[0].y2 = dy-1;
zone_count = 1;
return;
}
overlap_zones(zone_list,&zone_count); /* remove overlap */
if (order == COLUMN_MAJOR)
{
for (i = 0 ; i < zone_count-1 ; i++)
{ /* sort on x1 */
for (j = i+1 ; j < zone_count ; j++)
{
if (zone_list[j].x1 < zone_list[i].x1)
{
temp = zone_list[i];
zone_list[i] = zone_list[j];
zone_list[j] = temp;
}
}
}
for (i = 0 ; i < zone_count-1 ; i++)
{ /* order zones left to right, up to down */
x = zone_list[i].x2;
y = zone_list[i].y1;
fudge_x = zone_list[i].x1+dx/20; /* 5% slippage on alignment */
for (j = i+1, index = -1 ; j < zone_count ; j++)
{ /* find any zones above and within x extent of zone_list[i] */
if (zone_list[j].x1 > x)
break;
if (zone_list[j].y1 < y && zone_list[j].x1 <= fudge_x)
{
x = zone_list[j].x2;
y = zone_list[j].y1;
index = j;
}
}
if (index != -1)
{
temp = zone_list[i];
zone_list[i] = zone_list[index];
zone_list[index] = temp;
}
}
}
else /* ROW_MAJOR */
{ /* already sorted in y1 order */
for (i = 0 ; i < zone_count-1 ; i++)
{ /* order zones up to down, left to right */
y = zone_list[i].y2;
x = zone_list[i].x1;
fudge_y = zone_list[i].y1+dy/20; /* 5% slippage on alignment */
for (j = i+1, index = -1 ; j < zone_count ; j++)
{ /* find any zones left of and within y extent of zone_list[i] */
if (zone_list[j].y1 > y)
break;
if (zone_list[j].x1 < x && zone_list[j].y1 <= fudge_y)
{
y = zone_list[j].y2;
x = zone_list[j].x1;
index = j;
}
}
if (index != -1)
{
temp = zone_list[i];
zone_list[i] = zone_list[index];
zone_list[index] = temp;
}
}
}
}
/************************************************
* function: static int extract_zone(unsigned char *image,int dx,int dy,int x,int y,ZONE *zone_ptr)
* Extracts a rectangular region from the buffer starting at a point. It does
* this by wlaking the perimeter, recording the min and max x/y dimensions.
* If the region is big enough to be significant, it is saved as a zone and then
* whited out so it won't be reconsidered.
* parameters: pointer to image buffer and dx/dy extents of that buffer.
* x & y point to start extracting the zone.
* pointer to storage for zone
* returns: 1 if zone OK or 0 if not
************************************************/
static int extract_zone(unsigned char *image,int dx,int dy,int x,int y,ZONE *zone_ptr)
{
int ix,iy,minx,miny,maxx,maxy; /* perimeter variables & min/max values */
HEADING dir; /* current direction */
unsigned char *previous,*next,*here; /* buffer pointers */
minx = maxx = ix = x; /* preset min/max x/y and perimeter vars */
miny = maxy = iy = y;
dir = GOING_UP; /* starting direction */
do /* walk perimeter, recording min/max of rectangular region */
{
if (ix < minx) /* update min/max */
minx = ix;
if (ix > maxx)
maxx = ix;
if (iy < miny)
miny = iy;
if (iy > maxy)
maxy = iy;
here = image + iy * dx + ix; /* where are we? */
next = here + dx;
previous = here - dx;
switch (dir) /* based on current direction, */
{ /* look around for next direction */
case GOING_UP:
if (ix > 0 && *(here-1))
{
ix--;
dir = GOING_LEFT;
break;
}
if (iy > 0 && *previous)
{
iy--;
break;
}
if (ix < dx-1 && *(here+1))
{
ix++;
dir = GOING_RIGHT;
break;
}
if (iy < dy-1 && *next)
{
iy++;
dir = GOING_DOWN;
break;
}
break;
case GOING_RIGHT:
if (iy > 0 && *previous)
{
iy--;
dir = GOING_UP;
break;
}
if (ix < dx-1 && *(here+1))
{
ix++;
break;
}
if (iy < dy-1 && *next)
{
iy++;
dir = GOING_DOWN;
break;
}
if (ix > 0 && *(here-1))
{
ix--;
dir = GOING_LEFT;
break;
}
break;
case GOING_DOWN:
if (ix < dx-1 && *(here+1))
{
ix++;
dir = GOING_RIGHT;
break;
}
if (iy < dy-1 && *next)
{
iy++;
break;
}
if (ix > 0 && *(here-1))
{
ix--;
dir = GOING_LEFT;
break;
}
if (iy > 0 && *previous)
{
iy--;
dir = GOING_UP;
break;
}
break;
case GOING_LEFT:
if (iy < dy-1 && *next)
{
iy++;
dir = GOING_DOWN;
break;
}
if (ix > 0 && *(here-1))
{
ix--;
break;
}
if (iy > 0 && *previous)
{
iy--;
dir = GOING_UP;
break;
}
if (ix < dx-1 && *(here+1))
{
ix++;
dir = GOING_RIGHT;
break;
}
break;
}
} while (ix != x || iy != y); /* until we return to the start */
for (iy=miny, here=image+miny*dx+minx ; iy <= maxy ; iy++, here+=dx)
memset(here,WHITE,maxx-minx+1); /* whiteout the region */
if ((maxx-minx+1 < MIN_X_ZONE) || (maxy-miny+1 < MIN_Y_ZONE))
return 0; /* big enough? */
if (minx > 0) /* expand dimensions by one pixel */
minx--;
if (maxx < dx-1)
maxx++;
if (miny > 0)
miny--;
if (maxy < dy-1)
maxy++;
zone_ptr->x1 = minx; /* save zone */
zone_ptr->y1 = miny;
zone_ptr->x2 = maxx;
zone_ptr->y2 = maxy;
return 1;
}
/************************************************
* function: static void overlap_zones(ZONE *zone_array,int *array_size)
* find zones that overlap and combine them
* parameters: pointer to array of zones and pointer to count of zones
* returns: nothing
************************************************/
static void overlap_zones(ZONE *zone_array,int *array_size)
{
int i,j,ax1,ay1,ax2,ay2,bx1,by1,bx2,by2;
for (i = 0 ; i < *array_size-1 ; i++)
{ /* compare each zone against the rest */
ax1 = (zone_array+i)->x1;
ay1 = (zone_array+i)->y1;
ax2 = (zone_array+i)->x2;
ay2 = (zone_array+i)->y2;
for (j = i+1 ; j < *array_size ; j++)
{
bx1 = (zone_array+j)->x1;
by1 = (zone_array+j)->y1;
bx2 = (zone_array+j)->x2;
by2 = (zone_array+j)->y2;
if ((bx1>=ax2) || (ax1>=bx2) || (by1>=ay2) || (ay1>=by2))
continue; /* no overlap */
bx1 = min(bx1,ax1); /* combine zones */
by1 = min(by1,ay1);
bx2 = max(bx2,ax2);
by2 = max(by2,ay2);
(zone_array+i)->x1 = bx1;
(zone_array+i)->y1 = by1;
(zone_array+i)->x2 = bx2;
(zone_array+i)->y2 = by2;
(*array_size)--; /* new zone count */
memmove((char *)(zone_array+j),(char *)(zone_array+j+1),
sizeof(ZONE)*(*array_size-j)); /* shift array to remove zone */
i = -1; /* start all over */
break;
}
}
}