sergiotarxz/libvips
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

much faster clustering in im_aconv()

Browse Source 
cluster lines in batches to avoid rescanning the whole space each time
This commit is contained in:
John Cupitt 2011-06-10 12:02:33 +01:00
parent 953a315755
commit c605153852
1 changed files with 93 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

114
libvips/convolution/im_aconv.c
View File

@ -103,6 +103,11 @@ $ vips im_max abs.v
*/
#define MAX_LINES (10000)
/* The number of edges we consider at once in clustering. Higher values are
* faster, but risk pushing up average error in the result.
*/
#define MAX_EDGES (10)
/* Get an (x,y) value from a mask.
*/
#define MASK( M, X, Y ) ((M)->coeff[(X) + (Y) * (M)->xsize])
@ -121,6 +126,19 @@ typedef struct _HLine {
int weight;
} HLine;
/* For clustering. A pair of hlines and their distance. An edge in a graph.
*/
typedef struct _Edge {
/* The index into boxes->hline[].
*/
int a;
int b;
/* The distance between them, see boxes_distance().
*/
int d;
} Edge;
/* An element of a vline.
*/
typedef struct _VElement {
@ -165,6 +183,10 @@ typedef struct _Boxes {
int n_hline;
HLine hline[MAX_LINES];
/* During clustering, the top few edges we are considering.
*/
Edge edge[MAX_EDGES];
/* Scale and sum a set of hlines to make the final value.
*/
int n_velement;
@ -262,44 +284,93 @@ boxes_merge( Boxes *boxes, int a, int b )
boxes->hline[b].weight = 0;
}
/* Find the closest pair of hlines, join them up if the distance is less than
* a threshold. Return non-zero if we made a change.
static int
edge_sortfn( const void *p1, const void *p2 )
{
Edge *a = (Edge *) p1;
Edge *b = (Edge *) p2;
return( a->d - b->d );
}
/* Cluster in batches. Return non-zero if we merged some lines.
*
* This is not as accurate as rescanning the whole space on every merge, but
* it's far faster.
*/
static int
boxes_cluster( Boxes *boxes, int cluster )
boxes_cluster2( Boxes *boxes, int cluster )
{
int i, j;
int best, a, b;
int acted;
int i, j, k;
int worst;
int worst_i;
int merged;
best = 9999999;
for( i = 0; i < MAX_EDGES; i++ ) {
boxes->edge[i].a = -1;
boxes->edge[i].b = -1;
boxes->edge[i].d = 99999;
}
worst_i = 0;
worst = boxes->edge[worst_i].d;
for( i = 0; i < boxes->n_hline; i++ ) {
if( boxes->hline[i].weight == 0 )
continue;
for( j = i + 1; j < boxes->n_hline; j++ ) {
int d;
int distance;
if( boxes->hline[j].weight == 0 )
continue;
d = boxes_distance( boxes, i, j );
if( d < best ) {
best = d;
a = i;
b = j;
distance = boxes_distance( boxes, i, j );
if( distance < worst ) {
boxes->edge[worst_i].a = i;
boxes->edge[worst_i].b = j;
boxes->edge[worst_i].d = distance;
worst_i = 0;
worst = boxes->edge[worst_i].d;
for( k = 0; k < MAX_EDGES; k++ )
if( boxes->edge[k].d > worst ) {
worst = boxes->edge[k].d;
worst_i = k;
}
}
}
}
acted = 0;
if( best < cluster ) {
boxes_merge( boxes, a, b );
acted = 1;
/* Sort to get closest first.
*/
qsort( boxes->edge, MAX_EDGES, sizeof( Edge ), edge_sortfn );
/*
printf( "edges:\n" );
printf( " n a b d:\n" );
for( i = 0; i < MAX_EDGES; i++ )
printf( "%2i) %3d %3d %3d\n", i,
boxes->edge[i].a, boxes->edge[i].b, boxes->edge[i].d );
*/
/* Merge from the top down.
*/
merged = 0;
for( k = 0; k < MAX_EDGES; k++ ) {
Edge *edge = &boxes->edge[k];
if( edge->d > cluster )
break;
if( boxes->hline[edge->a].weight == 0 )
continue;
if( boxes->hline[edge->b].weight == 0 )
continue;
boxes_merge( boxes, edge->a, edge->b );
merged = 1;
}
return( acted );
return( merged );
}
/* Renumber after clustering. We will have removed a lot of hlines ... shuffle
@ -334,7 +405,7 @@ boxes_renumber( Boxes *boxes )
/* Sort by band, then factor, then row.
*/
static int
sortfn( const void *p1, const void *p2 )
velement_sortfn( const void *p1, const void *p2 )
{
VElement *a = (VElement *) p1;
VElement *b = (VElement *) p2;
@ -355,7 +426,8 @@ boxes_vline( Boxes *boxes )
/* Sort to get elements which could form a vline together.
*/
qsort( boxes->velement, boxes->n_velement, sizeof( VElement ), sortfn );
qsort( boxes->velement, boxes->n_velement, sizeof( VElement ),
velement_sortfn );
boxes->n_vline = 0;
for( y = 0; y < boxes->n_velement; ) {
@ -552,7 +624,7 @@ boxes_new( IMAGE *in, IMAGE *out, DOUBLEMASK *mask, int n_layers, int cluster )
VIPS_DEBUG_MSG( "boxes_new: clustering with thresh %d ...\n",
cluster );
while( boxes_cluster( boxes, cluster ) )
while( boxes_cluster2( boxes, cluster ) )
;
VIPS_DEBUG_MSG( "boxes_new: renumbering ...\n" );
boxes_renumber( boxes );