VipsMin stops early if it can

if VipsMin sees a minimum value (eg. 0 for uchar) it'll stop searching
early

ChangeLog

@@ -6,6 +6,7 @@
 - added optional output args, eg. x/y for min
 - CLI supports optional output args
 - in im_vips2tiff, enable YCbCr compression for jpeg write
+- VipsMin stops search early if it can
 
 10/8/11 started 7.26.3
 - don't use G_VALUE_COLLECT_INIT(), many platforms do not have a glib this

TODO

@@ -37,10 +37,6 @@
 
 
 
-- max.c will need an early termination thing for vips_sink ... easy?
-
-
-
 - support planar tiff
 
 

libvips/arithmetic/min.c

@@ -17,6 +17,8 @@
  * 	- rewrite, from im_maxpos()
  * 30/8/11
  * 	- rewrite as a class
+ * 5/9/11
+ * 	- abandon scan if we find minimum possible value
  */
 
 /*
@@ -57,6 +59,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>
+#include <limits.h>
 
 #include <vips/vips.h>
 #include <vips/internal.h>
@@ -178,6 +181,8 @@ vips_min_stop( VipsStatistic *statistic, void *seq )
 	return( 0 );
 }
 
+/* real min with no limits.
+ */
 #define LOOP( TYPE ) { \
 	TYPE *p = (TYPE *) in; \
 	TYPE m; \
@@ -199,6 +204,31 @@ vips_min_stop( VipsStatistic *statistic, void *seq )
 	min->set = TRUE; \
 } 
 
+/* real min with a lower bound.
+ */
+#define LOOPL( TYPE, LOWER ) { \
+	TYPE *p = (TYPE *) in; \
+	TYPE m; \
+	\
+	if( min->set ) \
+		m = min->min; \
+	else \
+		m = p[0]; \
+	\
+	for( i = 0; i < sz; i++ ) { \
+		if( p[i] < m ) { \
+			m = p[i]; \
+			min->x = x + i / bands; \
+			min->y = y; \
+			if( m <= LOWER ) \
+				statistic->stop = TRUE; \
+		} \
+	} \
+	\
+	min->min = m; \
+	min->set = TRUE; \
+} 
+
 #define CLOOP( TYPE ) { \
 	TYPE *p = (TYPE *) in; \
 	double m; \
@@ -239,14 +269,16 @@ vips_min_scan( VipsStatistic *statistic, void *seq,
 	int i;
 
 	switch( vips_image_get_format( input ) ) {
-	case IM_BANDFMT_UCHAR:		LOOP( unsigned char ); break; 
+	case IM_BANDFMT_UCHAR:		LOOPL( unsigned char, 0 ); break; 
-	case IM_BANDFMT_CHAR:		LOOP( signed char ); break; 
+	case IM_BANDFMT_CHAR:		LOOPL( signed char, SCHAR_MIN ); break; 
-	case IM_BANDFMT_USHORT:		LOOP( unsigned short ); break; 
+	case IM_BANDFMT_USHORT:		LOOPL( unsigned short, 0 ); break; 
-	case IM_BANDFMT_SHORT:		LOOP( signed short ); break; 
+	case IM_BANDFMT_SHORT:		LOOPL( signed short, SHRT_MIN ); break; 
-	case IM_BANDFMT_UINT:		LOOP( unsigned int ); break;
+	case IM_BANDFMT_UINT:		LOOPL( unsigned int, 0 ); break;
-	case IM_BANDFMT_INT:		LOOP( signed int ); break; 
+	case IM_BANDFMT_INT:		LOOPL( signed int, INT_MIN ); break; 
+
 	case IM_BANDFMT_FLOAT:		LOOP( float ); break; 
 	case IM_BANDFMT_DOUBLE:		LOOP( double ); break; 
+
 	case IM_BANDFMT_COMPLEX:	CLOOP( float ); break; 
 	case IM_BANDFMT_DPCOMPLEX:	CLOOP( double ); break; 
 

libvips/arithmetic/statistic.c

@@ -35,7 +35,7 @@
  */
 
 /*
-#define DEBUG
+#define VIPS_DEBUG
  */
 
 #ifdef HAVE_CONFIG_H
@@ -48,6 +48,7 @@
 #include <math.h>
 
 #include <vips/vips.h>
+#include <vips/debug.h>
 
 #include "statistic.h"
 
@@ -86,6 +87,9 @@ vips_statistic_scan( VipsRegion *region,
 	int y;
 	PEL *p;
 
+	VIPS_DEBUG_MSG( "vips_statistic_scan: %d x %d @ %d x %d\n",
+		r->width, r->height, r->left, r->top );
+
 	p = (PEL *) IM_REGION_ADDR( region, r->left, r->top ); 
 	for( y = 0; y < r->height; y++ ) { 
 		if( class->scan( statistic,