/* Copyright (C) 2001-2007 Peter Selinger.
* This file is part of Potrace. It is free software and it is covered
* by the GNU General Public License. See the file COPYING for details. */
/* $Id: decompose.c 146 2007-04-09 00:43:46Z selinger $ */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <potracelib.h>
#include <curve.h>
#include <lists.h>
#include <auxiliary.h>
#include <bitmap.h>
#include <decompose.h>
#include <progress.h>
/* ---------------------------------------------------------------------- */
/* auxiliary bitmap manipulations */
/* set the excess padding to 0 */
static void bm_clearexcess( potrace_bitmap_t* bm )
{
potrace_word mask;
int y;
if( bm->w % BM_WORDBITS != 0 )
{
mask = BM_ALLBITS << ( BM_WORDBITS - (bm->w % BM_WORDBITS) );
for( y = 0; y<bm->h; y++ )
{
*bm_index( bm, bm->w, y ) &= mask;
}
}
}
struct bbox_s
{
int x0, x1, y0, y1; /* bounding box */
};
typedef struct bbox_s bbox_t;
/* clear the bm, assuming the bounding box is set correctly (faster
* than clearing the whole bitmap) */
static void clear_bm_with_bbox( potrace_bitmap_t* bm, bbox_t* bbox )
{
int imin = (bbox->x0 / BM_WORDBITS);
int imax = ( (bbox->x1 + BM_WORDBITS - 1) / BM_WORDBITS );
int i, y;
for( y = bbox->y0; y<bbox->y1; y++ )
{
for( i = imin; i<imax; i++ )
{
bm_scanline( bm, y )[i] = 0;
}
}
}
/* ---------------------------------------------------------------------- */
/* auxiliary functions */
/* deterministically and efficiently hash (x,y) into a pseudo-random bit */
static inline int detrand( int x, int y )
{
unsigned int z;
static const unsigned char t[256] =
{
/* non-linear sequence: constant term of inverse in GF(8),
* mod x^8+x^4+x^3+x+1 */
0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1,
0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0,
0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1,
1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 1, 1,
0, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 0,
0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0,
0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0,
0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1,
1, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0,
0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 1,
1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
};
/* 0x04b3e375 and 0x05a8ef93 are chosen to contain every possible
* 5-bit sequence */
z = ( (0x04b3e375 * x) ^ y ) * 0x05a8ef93;
z = t[z & 0xff] ^ t[(z >> 8) & 0xff] ^ t[(z >> 16) & 0xff] ^ t[(z >> 24) & 0xff];
return z & 1;
}
/* return the "majority" value of bitmap bm at intersection (x,y). We
* assume that the bitmap is balanced at "radius" 1. */
static int majority( potrace_bitmap_t* bm, int x, int y )
{
int i, a, ct;
for( i = 2; i<5; i++ ) /* check at "radius" i */
{
ct = 0;
for( a = -i + 1; a<=i - 1; a++ )
{
ct += BM_GET( bm, x + a, y + i - 1 ) ? 1 : -1;
ct += BM_GET( bm, x + i - 1, y + a - 1 ) ? 1 : -1;
ct += BM_GET( bm, x + a - 1, y - i ) ? 1 : -1;
ct += BM_GET( bm, x - i, y + a ) ? 1 : -1;
}
if( ct>0 )
{
return 1;
}
else if( ct<0 )
{
return 0;
}
}
return 0;
}
/* ---------------------------------------------------------------------- */
/* decompose image into paths */
/* efficiently invert bits [x,infty) and [xa,infty) in line y. Here xa
* must be a multiple of BM_WORDBITS. */
static void xor_to_ref( potrace_bitmap_t* bm, int x, int y, int xa )
{
int xhi = x & - BM_WORDBITS;
int xlo = x & (BM_WORDBITS - 1); /* = x % BM_WORDBITS */
int i;
if( xhi<xa )
{
for( i = xhi; i < xa; i += BM_WORDBITS )
{
*bm_index( bm, i, y ) ^= BM_ALLBITS;
}
}
else
{
for( i = xa; i < xhi; i += BM_WORDBITS )
{
*bm_index( bm, i, y ) ^= BM_ALLBITS;
}
}
/* note: the following "if" is needed because x86 treats a<<b as
* a<<(b&31). I spent hours looking for this bug. */
if( xlo )
{
*bm_index( bm, xhi, y ) ^= ( BM_ALLBITS << (BM_WORDBITS - xlo) );
}
}
/* a path is represented as an array of points, which are thought to
* lie on the corners of pixels (not on their centers). The path point
* (x,y) is the lower left corner of the pixel (x,y). Paths are
* represented by the len/pt components of a path_t object (which
* also stores other information about the path) */
/* xor the given pixmap with the interior of the given path. Note: the
* path must be within the dimensions of the pixmap. */
static void xor_path( potrace_bitmap_t* bm, path_t* p )
{
int xa, x, y, k, y1;
if( p->priv->len <= 0 ) /* a path of length 0 is silly, but legal */
{
return;
}
y1 = p->priv->pt[p->priv->len - 1].y;
xa = p->priv->pt[0].x & - BM_WORDBITS;
for( k = 0; k<p->priv->len; k++ )
{
x = p->priv->pt[k].x;
y = p->priv->pt[k].y;
if( y != y1 )
{
/* efficiently invert the rectangle [x,xa] x [y,y1] */
xor_to_ref( bm, x, min( y, y1 ), xa );
y1 = y;
}
}
}
/* Find the bounding box of a given path. Path is assumed to be of
* non-zero length. */
static void setbbox_path( bbox_t* bbox, path_t* p )
{
int x, y;
int k;
bbox->y0 = INT_MAX;
bbox->y1 = 0;
bbox->x0 = INT_MAX;
bbox->x1 = 0;
for( k = 0; k<p->priv->len; k++ )
{
x = p->priv->pt[k].x;
y = p->priv->pt[k].y;
if( x < bbox->x0 )
{
bbox->x0 = x;
}
if( x > bbox->x1 )
{
bbox->x1 = x;
}
if( y < bbox->y0 )
{
bbox->y0 = y;
}
if( y > bbox->y1 )
{
bbox->y1 = y;
}
}
}
/* compute a path in the given pixmap, separating black from white.
* Start path at the point (x0,x1), which must be an upper left corner
* of the path. Also compute the area enclosed by the path. Return a
* new path_t object, or NULL on error (note that a legitimate path
* cannot have length 0). Sign is required for correct interpretation
* of turnpolicies. */
static path_t* findpath( potrace_bitmap_t* bm, int x0, int y0, int sign, int turnpolicy )
{
int x, y, dirx, diry, len, size, area;
int c, d, tmp;
point_t* pt, * pt1;
path_t* p = NULL;
x = x0;
y = y0;
dirx = 0;
diry = -1;
len = size = 0;
pt = NULL;
area = 0;
while( 1 )
{
/* add point to path */
if( len>=size )
{
size += 100;
size = (int) ( 1.3 * size );
pt1 = (point_t*) realloc( pt, size * sizeof(point_t) );
if( !pt1 )
{
goto error;
}
pt = pt1;
}
pt[len].x = x;
pt[len].y = y;
len++;
/* move to next point */
x += dirx;
y += diry;
area += x * diry;
/* path complete? */
if( x==x0 && y==y0 )
{
break;
}
/* determine next direction */
c = BM_GET( bm, x + (dirx + diry - 1) / 2, y + (diry - dirx - 1) / 2 );
d = BM_GET( bm, x + (dirx - diry - 1) / 2, y + (diry + dirx - 1) / 2 );
if( c && !d ) /* ambiguous turn */
{
if( turnpolicy == POTRACE_TURNPOLICY_RIGHT
|| (turnpolicy == POTRACE_TURNPOLICY_BLACK && sign == '+')
|| (turnpolicy == POTRACE_TURNPOLICY_WHITE && sign == '-')
|| ( turnpolicy == POTRACE_TURNPOLICY_RANDOM && detrand( x, y ) )
|| ( turnpolicy == POTRACE_TURNPOLICY_MAJORITY && majority( bm, x, y ) )
|| ( turnpolicy == POTRACE_TURNPOLICY_MINORITY && !majority( bm, x, y ) ) )
{
tmp = dirx; /* right turn */
dirx = diry;
diry = -tmp;
}
else
{
tmp = dirx; /* left turn */
dirx = -diry;
diry = tmp;
}
}
else if( c ) /* right turn */
{
tmp = dirx;
dirx = diry;
diry = -tmp;
}
else if( !d ) /* left turn */
{
tmp = dirx;
dirx = -diry;
diry = tmp;
}
} /* while this path */
/* allocate new path object */
p = path_new();
if( !p )
{
goto error;
}
p->priv->pt = pt;
p->priv->len = len;
p->area = area;
p->sign = sign;
return p;
error:
free( pt );
return NULL;
}
/* Give a tree structure to the given path list, based on "insideness"
* testing. I.e., path A is considered "below" path B if it is inside
* path B. The input pathlist is assumed to be ordered so that "outer"
* paths occur before "inner" paths. The tree structure is stored in
* the "childlist" and "sibling" components of the path_t
* structure. The linked list structure is also changed so that
* negative path components are listed immediately after their
* positive parent. Note: some backends may ignore the tree
* structure, others may use it e.g. to group path components. We
* assume that in the input, point 0 of each path is an "upper left"
* corner of the path, as returned by bm_to_pathlist. This makes it
* easy to find an "interior" point. The bm argument should be a
* bitmap of the correct size (large enough to hold all the paths),
* and will be used as scratch space. Return 0 on success or -1 on
* error with errno set. */
static void pathlist_to_tree( path_t* plist, potrace_bitmap_t* bm )
{
path_t* p, * p1;
path_t* heap, * heap1;
path_t* cur;
path_t* head;
path_t** hook, ** hook_in, ** hook_out; /* for fast appending to linked list */
bbox_t bbox;
bm_clear( bm, 0 );
/* save original "next" pointers */
list_forall( p, plist ) {
p->sibling = p->next;
p->childlist = NULL;
}
heap = plist;
/* the heap holds a list of lists of paths. Use "childlist" field
* for outer list, "next" field for inner list. Each of the sublists
* is to be turned into a tree. This code is messy, but it is
* actually fast. Each path is rendered exactly once. We use the
* heap to get a tail recursive algorithm: the heap holds a list of
* pathlists which still need to be transformed. */
while( heap )
{
/* unlink first sublist */
cur = heap;
heap = heap->childlist;
cur->childlist = NULL;
/* unlink first path */
head = cur;
cur = cur->next;
head->next = NULL;
/* render path */
xor_path( bm, head );
setbbox_path( &bbox, head );
/* now do insideness test for each element of cur; append it to
* head->childlist if it's inside head, else append it to
* head->next. */
hook_in = &head->childlist;
hook_out = &head->next;
list_forall_unlink( p, cur ) {
if( p->priv->pt[0].y <= bbox.y0 )
{
list_insert_beforehook( p, hook_out );
/* append the remainder of the list to hook_out */
*hook_out = cur;
break;
}
if( BM_GET( bm, p->priv->pt[0].x, p->priv->pt[0].y - 1 ) )
{
list_insert_beforehook( p, hook_in );
}
else
{
list_insert_beforehook( p, hook_out );
}
}
/* clear bm */
clear_bm_with_bbox( bm, &bbox );
/* now schedule head->childlist and head->next for further
* processing */
if( head->next )
{
head->next->childlist = heap;
heap = head->next;
}
if( head->childlist )
{
head->childlist->childlist = heap;
heap = head->childlist;
}
}
/* copy sibling structure from "next" to "sibling" component */
p = plist;
while( p )
{
p1 = p->sibling;
p->sibling = p->next;
p = p1;
}
/* reconstruct a new linked list ("next") structure from tree
* ("childlist", "sibling") structure. This code is slightly messy,
* because we use a heap to make it tail recursive: the heap
* contains a list of childlists which still need to be
* processed. */
heap = plist;
if( heap )
{
heap->next = NULL; /* heap is a linked list of childlists */
}
plist = NULL;
hook = &plist;
while( heap )
{
heap1 = heap->next;
for( p = heap; p; p = p->sibling )
{
/* p is a positive path */
/* append to linked list */
list_insert_beforehook( p, hook );
/* go through its children */
for( p1 = p->childlist; p1; p1 = p1->sibling )
{
/* append to linked list */
list_insert_beforehook( p1, hook );
/* append its childlist to heap, if non-empty */
if( p1->childlist )
{
list_append( path_t, heap1, p1->childlist );
}
}
}
heap = heap1;
}
return;
}
/* find the next set pixel in a row <= y. Pixels are searched first
* left-to-right, then top-down. In other words, (x,y)<(x',y') if y>y'
* or y=y' and x<x'. If found, return 0 and store pixel in
* (*xp,*yp). Else return 1. Note that this function assumes that
* excess bytes have been cleared with bm_clearexcess. */
static int findnext( potrace_bitmap_t* bm, int* xp, int* yp )
{
int x;
int y;
for( y = *yp; y>=0; y-- )
{
for( x = 0; x<bm->w; x += BM_WORDBITS )
{
if( *bm_index( bm, x, y ) )
{
while( !BM_GET( bm, x, y ) )
{
x++;
}
/* found */
*xp = x;
*yp = y;
return 0;
}
}
}
/* not found */
return 1;
}
/* Decompose the given bitmap into paths. Returns a linked list of
* path_t objects with the fields len, pt, area, sign filled
* in. Returns 0 on success with plistp set, or -1 on error with errno
* set. */
int bm_to_pathlist( const potrace_bitmap_t* bm,
path_t** plistp,
const potrace_param_t* param,
progress_t* progress )
{
int x;
int y;
path_t* p;
path_t* plist = NULL; /* linked list of path objects */
path_t** hook = &plist; /* used to speed up appending to linked list */
potrace_bitmap_t* bm1 = NULL;
int sign;
bm1 = bm_dup( bm );
if( !bm1 )
{
goto error;
}
/* be sure the byte padding on the right is set to 0, as the fast
* pixel search below relies on it */
bm_clearexcess( bm1 );
/* iterate through components */
y = bm1->h - 1;
while( findnext( bm1, &x, &y ) == 0 )
{
/* calculate the sign by looking at the original */
sign = BM_GET( bm, x, y ) ? '+' : '-';
/* calculate the path */
p = findpath( bm1, x, y + 1, sign, param->turnpolicy );
if( p==NULL )
{
goto error;
}
/* update buffered image */
xor_path( bm1, p );
/* if it's a turd, eliminate it, else append it to the list */
if( p->area <= param->turdsize )
{
path_free( p );
}
else
{
list_insert_beforehook( p, hook );
}
if( bm1->h > 0 ) /* to be sure */
{
progress_update( 1 - y / (double) bm1->h, progress );
}
}
pathlist_to_tree( plist, bm1 );
bm_free( bm1 );
*plistp = plist;
progress_update( 1.0, progress );
return 0;
error:
bm_free( bm1 );
list_forall_unlink( p, plist ) {
path_free( p );
}
return -1;
}