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only save tiles more than 5 from blank 

looks for max absolute difference
This commit is contained in:
John Cupitt 2016-04-26 10:06:59 +01:00
parent 5e933fe8e9
commit 8a31df3214
1 changed files with 9 additions and 3 deletions
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12
libvips/foreign/dzsave.c
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@ -56,7 +56,7 @@
* 9/9/15
* - better overlap handling, thanks robclouth
* 24/11/15
* - don't write empty tiles in google mode
* - don't write almost blank tiles in google mode
* 25/11/15
* - always strip tile metadata
* 16/12/15
@ -1104,6 +1104,12 @@ tile_name( Layer *layer, int x, int y )
return( out );
}
/* Test for tile equal to background colour. In google maps mode, we skip
* blank background tiles.
*
* Don't use exactly equality, since compression artefacts or noise can upset
* this.
*/
static gboolean
tile_equal( VipsImage *image, VipsPel * restrict ink )
{
@ -1131,7 +1137,7 @@ tile_equal( VipsImage *image, VipsPel * restrict ink )
for( x = 0; x < image->Xsize; x++ ) {
for( b = 0; b < bytes; b++ )
if( p[b] != ink[b] ) {
if( VIPS_ABS( p[b] - ink[b] ) > 5 ) {
g_object_unref( region );
return( FALSE );
}
@ -1206,10 +1212,10 @@ strip_work( VipsThreadState *state, void *a )
g_object_unref( x );
#ifdef DEBUG_VERBOSE
#endif /*DEBUG_VERBOSE*/
printf( "strip_work: skipping blank tile %d x %d\n",
state->x / dz->tile_size,
state->y / dz->tile_size );
#endif /*DEBUG_VERBOSE*/
return( 0 );
}