im_avg() is a class

ChangeLog

@@ -1,6 +1,6 @@
 20/8/11 started 7.27.0
 - version bump for new dev cycle
-- im_subtract() redone as a class
+- im_subtract(), im_avg() redone as classes
 
 10/8/11 started 7.26.3
 - don't use G_VALUE_COLLECT_INIT(), many platforms do not have a glib this

TODO

@@ -1,3 +1,36 @@
+- is our C API too awkward? we'll need
+
+	if( !(c = vips_add( a, b )) ||
+		!(d = vips_add( a, c )) )
+		return NULL;
+
+  seems wordy compared to 
+
+	if( vips_add( a, b, &c ) ||
+		vips_add( a, c, &d ) )
+		return -1;
+
+  plus VipsPool will be more natural with #2, I think, and things like
+  vips_avg() have to be form #2
+
+
+
+
+- could we generate the code for vips_add() automatically? it might be nice to
+  have them all in one place at least
+
+
+
+
+- all the old dispatch wrappers could move to deprecated
+
+
+
+
+- max.c will need an early termination thing for vips_sink ... easy?
+
+
+
 - support planar tiff
 
 

libvips/arithmetic/Makefile.am

@@ -3,7 +3,6 @@ noinst_LTLIBRARIES = libarithmetic.la
 libarithmetic_la_SOURCES = \
 	arith_dispatch.c \
 	im_abs.c \
-	im_avg.c \
 	im_bandmean.c \
 	im_cross_phase.c \
 	im_deviate.c \
@@ -22,6 +21,9 @@ libarithmetic_la_SOURCES = \
 	im_remainder.c \
 	im_sign.c \
 	im_stats.c \
+	statistic.c \
+	statistic.h \
+	avg.c \
 	subtract.c \
 	math.c \
 	arithmetic.c \

libvips/arithmetic/add.c

@@ -192,12 +192,14 @@ add_buffer( VipsBinary *binary, PEL *out, PEL *left, PEL *right, int width )
 
 	/* Complex just doubles the size.
 	 */
-	const int sz = width * im->Bands * 
+	const int sz = width * vips_image_get_bands( im ) * 
-		(vips_band_format_iscomplex( im->BandFmt ) ? 2 : 1);
+		(vips_band_format_iscomplex( vips_image_get_format( im ) ) ? 
+		 	2 : 1);
 
 	VipsVector *v;
 
-	if( (v = vips_arithmetic_get_vector( class, im->BandFmt )) ) {
+	if( (v = vips_arithmetic_get_vector( class, 
+		vips_image_get_format( im ) )) ) {
 		VipsExecutor ex;
 
 		vips_executor_set_program( &ex, v, sz );
@@ -213,7 +215,7 @@ add_buffer( VipsBinary *binary, PEL *out, PEL *left, PEL *right, int width )
 		/* Add all input types. Keep types here in sync with 
 		 * bandfmt_add[] below.
 		 */
-		switch( im->BandFmt ) {
+		switch( vips_image_get_format( im ) ) {
 		case VIPS_FORMAT_UCHAR: 	
 			LOOP( unsigned char, unsigned short ); break; 
 		case VIPS_FORMAT_CHAR: 	
@@ -243,21 +245,21 @@ add_buffer( VipsBinary *binary, PEL *out, PEL *left, PEL *right, int width )
 
 /* Save a bit of typing.
  */
-#define UC IM_BANDFMT_UCHAR
+#define UC VIPS_FORMAT_UCHAR
-#define C IM_BANDFMT_CHAR
+#define C VIPS_FORMAT_CHAR
-#define US IM_BANDFMT_USHORT
+#define US VIPS_FORMAT_USHORT
-#define S IM_BANDFMT_SHORT
+#define S VIPS_FORMAT_SHORT
-#define UI IM_BANDFMT_UINT
+#define UI VIPS_FORMAT_UINT
-#define I IM_BANDFMT_INT
+#define I VIPS_FORMAT_INT
-#define F IM_BANDFMT_FLOAT
+#define F VIPS_FORMAT_FLOAT
-#define X IM_BANDFMT_COMPLEX
+#define X VIPS_FORMAT_COMPLEX
-#define D IM_BANDFMT_DOUBLE
+#define D VIPS_FORMAT_DOUBLE
-#define DX IM_BANDFMT_DPCOMPLEX
+#define DX VIPS_FORMAT_DPCOMPLEX
 
 /* Type promotion for addition. Sign and value preserving. Make sure these
  * match the case statement in add_buffer() above.
  */
-static int bandfmt_add[10] = {
+static const VipsBandFormat bandfmt_add[10] = {
 /* UC  C   US  S   UI  I  F  X  D  DX */
    US, S,  UI, I,  UI, I, F, X, D, DX
 };
@@ -314,6 +316,11 @@ vips_add_class_init( VipsAddClass *class )
 	bclass->process_line = add_buffer;
 }
 
+static void
+vips_add_init( VipsAdd *add )
+{
+}
+
 VipsImage *
 vips_add( VipsImage *in1, VipsImage *in2, ... )
 {
@@ -330,8 +337,3 @@ vips_add( VipsImage *in1, VipsImage *in2, ... )
 
 	return( out );
 }
-
-static void
-vips_add_init( VipsAdd *add )
-{
-}

libvips/arithmetic/arithmetic.c

@@ -144,7 +144,6 @@ vips_arithmetic_class_init( VipsArithmeticClass *class )
 	vips_object_class_install_argument( vobject_class, pspec,
 		VIPS_ARGUMENT_OPTIONAL_INPUT, 
 		G_STRUCT_OFFSET( VipsArithmetic, imtest ) );
-
 }
 
 static void
@@ -154,7 +153,7 @@ vips_arithmetic_init( VipsArithmetic *arithmetic )
 
 void 
 vips_arithmetic_set_format_table( VipsArithmeticClass *class, 
-	VipsBandFormat *format_table )
+	const VipsBandFormat *format_table )
 {
 	int i;
 
@@ -240,8 +239,10 @@ vips_arithmetic_operation_init( void )
 {
 	extern GType vips_add_get_type( void ); 
 	extern GType vips_subtract_get_type( void ); 
+	extern GType vips_avg_get_type( void ); 
 
 	vips_add_get_type();
 	vips_subtract_get_type();
+	vips_avg_get_type();
 }
 

libvips/arithmetic/arithmetic.h

@@ -75,7 +75,7 @@ typedef struct _VipsArithmeticClass {
 	/* For each input format, what output format. Used for arithmetic
 	 * too, since we cast inputs to match.
 	 */
-	VipsBandFormat *format_table;
+	const VipsBandFormat *format_table;
 
 	/* A vector program for each input type.
 	 */
@@ -89,7 +89,7 @@ typedef struct _VipsArithmeticClass {
 GType vips_arithmetic_get_type( void );
 
 void vips_arithmetic_set_format_table( VipsArithmeticClass *klass, 
-	VipsBandFormat *format_table );
+	const VipsBandFormat *format_table );
 VipsVector *vips_arithmetic_get_vector( VipsArithmeticClass *klass, 
 	VipsBandFormat fmt );
 void vips_arithmetic_compile( VipsArithmeticClass *klass ); 

libvips/arithmetic/avg.c

@@ -0,0 +1,279 @@
+/* avg ... average value of image
+ *
+ * Copyright: 1990, J. Cupitt
+ *
+ * Author: J. Cupitt
+ * Written on: 02/08/1990
+ * Modified on: 
+ * 5/5/93 JC
+ *	- now does partial images
+ *	- less likely to overflow
+ * 1/7/93 JC
+ *	- adapted for partial v2
+ *	- ANSI C
+ * 21/2/95 JC
+ *	- modernised again
+ * 11/5/95 JC
+ * 	- oops! return( NULL ) in im_avg(), instead of return( -1 )
+ * 20/6/95 JC
+ *	- now returns double
+ * 13/1/05
+ *	- use 64 bit arithmetic 
+ * 8/12/06
+ * 	- add liboil support
+ * 18/8/09
+ * 	- gtkdoc, minor reformatting
+ * 7/9/09
+ * 	- rewrite for im__wrapiter()
+ * 	- add complex case (needed for im_max())
+ * 8/9/09
+ * 	- wrapscan stuff moved here
+ * 31/7/10
+ * 	- remove liboil
+ * 24/8/11
+ * 	- rewrite as a class
+ */
+
+/*
+
+    This file is part of VIPS.
+    
+    VIPS is free software; you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+ */
+
+/*
+
+    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
+
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif /*HAVE_CONFIG_H*/
+#include <vips/intl.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include <vips/vips.h>
+#include <vips/internal.h>
+
+#include "statistic.h"
+
+#ifdef WITH_DMALLOC
+#include <dmalloc.h>
+#endif /*WITH_DMALLOC*/
+
+/**
+ * VipsAvg:
+ * @in: input #VipsImage
+ * @out: output pixel average
+ *
+ * This operation finds the average value in an image. It operates on all 
+ * bands of the input image: use im_stats() if you need to calculate an 
+ * average for each band. For complex images, return the average modulus.
+ *
+ * See also: im_stats(), im_bandmean(), im_deviate(), im_rank()
+ */
+
+/* Properties.
+ */
+enum {
+	PROP_OUTPUT = 1,
+	PROP_LAST
+}; 
+
+typedef struct _VipsAvg {
+	VipsStatistic parent_instance;
+
+	double sum;
+	double avg;
+} VipsAvg;
+
+typedef VipsStatisticClass VipsAvgClass;
+
+G_DEFINE_TYPE( VipsAvg, vips_avg, VIPS_TYPE_STATISTIC );
+
+static int
+vips_avg_build( VipsObject *object )
+{
+	VipsStatistic *statistic = VIPS_STATISTIC( object ); 
+	VipsImage *in = statistic->input; 
+	VipsAvg *avg = (VipsAvg *) object;
+
+	gint64 vals, pels;
+	double average;
+
+	if( VIPS_OBJECT_CLASS( vips_avg_parent_class )->build( object ) )
+		return( -1 );
+
+	/* Calculate average. For complex, we accumulate re*re +
+	 * im*im, so we need to sqrt.
+	 */
+	pels = (gint64) vips_image_get_width( in ) * 
+		vips_image_get_height( in ); 
+	vals = pels * vips_image_get_bands( in );
+	average = avg->sum / vals;
+	if( vips_bandfmt_iscomplex( vips_image_get_format( in ) ) )
+		average = sqrt( average );
+	g_object_set( object, "out", average, NULL );
+
+	return( 0 );
+}
+
+/* Start function: allocate space for a double in which we can accumulate the
+ * sum for this thread.
+ */
+static void *
+vips_avg_start( VipsStatistic *statistic )
+{
+	double *sum;
+
+	if( !(sum = VIPS_NEW( NULL, double )) ) 
+		return( NULL );
+	*sum = 0.0;
+
+	return( (void *) sum );
+}
+
+/* Stop function. Add this little sum to the main sum.
+ */
+static int
+vips_avg_stop( VipsStatistic *statistic, void *seq )
+{
+	VipsAvg *avg = (VipsAvg *) statistic;
+	double *sum = (double *) seq;
+
+	avg->sum += *sum;
+
+	vips_free( seq );
+
+	return( 0 );
+}
+
+/* Sum pels in this section.
+ */
+#define LOOP( TYPE ) { \
+	TYPE *p = (TYPE *) in; \
+	\
+	for( x = 0; x < sz; x++ ) \
+		m += p[x]; \
+}
+
+#define CLOOP( TYPE ) { \
+	TYPE *p = (TYPE *) in; \
+	\
+	for( x = 0; x < sz; x++ ) { \
+		double mod, re, im; \
+		\
+		re = p[0]; \
+		im = p[1]; \
+		p += 2; \
+		mod = re * re + im * im; \
+		\
+		m += mod; \
+	} \
+} 
+
+/* Loop over region, accumulating a sum in *tmp.
+ */
+static int
+vips_avg_scan( VipsStatistic *statistic, void *seq, void *in, int n )
+{
+	const VipsImage *im = statistic->input;
+	const int sz = n * vips_image_get_bands( im );
+
+	double *sum = (double *) seq;
+
+	int x;
+	double m;
+
+	m = *sum;
+
+	/* Now generate code for all types. 
+	 */
+	switch( vips_image_get_format( im ) ) {
+	case VIPS_FORMAT_UCHAR:		LOOP( unsigned char ); break; 
+	case VIPS_FORMAT_CHAR:		LOOP( signed char ); break; 
+	case VIPS_FORMAT_USHORT:	LOOP( unsigned short ); break; 
+	case VIPS_FORMAT_SHORT:		LOOP( signed short ); break; 
+	case VIPS_FORMAT_UINT:		LOOP( unsigned int ); break;
+	case VIPS_FORMAT_INT:		LOOP( signed int ); break; 
+	case VIPS_FORMAT_FLOAT:		LOOP( float ); break; 
+	case VIPS_FORMAT_DOUBLE:	LOOP( double ); break; 
+	case VIPS_FORMAT_COMPLEX:	CLOOP( float ); break; 
+	case VIPS_FORMAT_DPCOMPLEX:	CLOOP( double ); break; 
+
+	default: 
+		g_assert( 0 );
+	}
+
+	*sum = m;
+
+	return( 0 );
+}
+
+static void
+vips_avg_class_init( VipsAvgClass *class )
+{
+	GObjectClass *gobject_class = (GObjectClass *) class;
+	VipsObjectClass *object_class = (VipsObjectClass *) class;
+	VipsStatisticClass *sclass = VIPS_STATISTIC_CLASS( class );
+
+	GParamSpec *pspec;
+
+	gobject_class->set_property = vips_object_set_property;
+	gobject_class->get_property = vips_object_get_property;
+
+	object_class->nickname = "avg";
+	object_class->description = _( "find image average" );
+	object_class->build = vips_avg_build;
+
+	sclass->start = vips_avg_start;
+	sclass->scan = vips_avg_scan;
+	sclass->stop = vips_avg_stop;
+
+	pspec = g_param_spec_double( "out", "Output", 
+		_( "Output value" ),
+		-G_MAXDOUBLE,
+		G_MAXDOUBLE,
+		0.0,
+		G_PARAM_READWRITE );
+	g_object_class_install_property( gobject_class, 
+		PROP_OUTPUT, pspec );
+	vips_object_class_install_argument( object_class, pspec,
+		VIPS_ARGUMENT_REQUIRED_OUTPUT, 
+		G_STRUCT_OFFSET( VipsAvg, avg ) );
+}
+
+static void
+vips_avg_init( VipsAvg *avg )
+{
+}
+
+int
+vips_avg( VipsImage *in, double *out, ... )
+{
+	va_list ap;
+	int result;
+
+	va_start( ap, out );
+	result = vips_call_split( "avg", ap, in, out );
+	va_end( ap );
+
+	return( result );
+}

libvips/arithmetic/im_avg.c

@@ -1,296 +0,0 @@
-/* im_avg.c
- *
- * Copyright: 1990, J. Cupitt
- *
- * Author: J. Cupitt
- * Written on: 02/08/1990
- * Modified on: 
- * 5/5/93 JC
- *	- now does partial images
- *	- less likely to overflow
- * 1/7/93 JC
- *	- adapted for partial v2
- *	- ANSI C
- * 21/2/95 JC
- *	- modernised again
- * 11/5/95 JC
- * 	- oops! return( NULL ) in im_avg(), instead of return( -1 )
- * 20/6/95 JC
- *	- now returns double
- * 13/1/05
- *	- use 64 bit arithmetic 
- * 8/12/06
- * 	- add liboil support
- * 18/8/09
- * 	- gtkdoc, minor reformatting
- * 7/9/09
- * 	- rewrite for im__wrapiter()
- * 	- add complex case (needed for im_max())
- * 8/9/09
- * 	- wrapscan stuff moved here
- * 31/7/10
- * 	- remove liboil
- */
-
-/*
-
-    This file is part of VIPS.
-    
-    VIPS is free software; you can redistribute it and/or modify
-    it under the terms of the GNU Lesser General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU Lesser General Public License for more details.
-
-    You should have received a copy of the GNU Lesser General Public License
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
-
- */
-
-/*
-
-    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
-
- */
-
-#ifdef HAVE_CONFIG_H
-#include <config.h>
-#endif /*HAVE_CONFIG_H*/
-#include <vips/intl.h>
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <math.h>
-
-#include <vips/vips.h>
-#include <vips/internal.h>
-
-#ifdef WITH_DMALLOC
-#include <dmalloc.h>
-#endif /*WITH_DMALLOC*/
-
-typedef struct _Wrapscan {
-	IMAGE *in;
-	im_start_fn start; 
-	im__wrapscan_fn scan; 
-	im_stop_fn stop;
-	void *a; 
-	void *b;
-} Wrapscan;
-
-static void *
-wrapscan_start( VipsImage *in, void *a, void *b )
-{
-	Wrapscan *wrapscan = (Wrapscan *) a;
-
-	return( wrapscan->start( in, wrapscan->a, wrapscan->b ) );
-}
-
-static int
-wrapscan_stop( void *seq, void *a, void *b )
-{
-	Wrapscan *wrapscan = (Wrapscan *) a;
-
-	return( wrapscan->stop( seq, wrapscan->a, wrapscan->b ) );
-}
-
-static int
-wrapscan_scan( REGION *reg, void *seq, void *a, void *b )
-{
-	Wrapscan *wrapscan = (Wrapscan *) a;
-	Rect *r = &reg->valid;
-	int lsk = IM_REGION_LSKIP( reg );
-
-	int y;
-	PEL *p;
-
-	p = (PEL *) IM_REGION_ADDR( reg, r->left, r->top ); 
-	for( y = 0; y < r->height; y++ ) { 
-		if( wrapscan->scan( p, r->width, seq, 
-			wrapscan->a, wrapscan->b ) )
-			return( -1 );
-		p += lsk;
-	} 
-
-	return( 0 );
-}
-
-/* Like vips_sink(), but the scan function works a line at a time, like
- * im_wrap*(). Shared with im_min(), im_deviate() etc.
- */
-int
-im__wrapscan( VipsImage *in, 
-	VipsStart start, im__wrapscan_fn scan, VipsStop stop,
-	void *a, void *b )
-{
-	Wrapscan wrapscan;
-
-	wrapscan.in = in;
-	wrapscan.start = start;
-	wrapscan.scan = scan;
-	wrapscan.stop = stop;
-	wrapscan.a = a;
-	wrapscan.b = b;
-
-	return( vips_sink( in, 
-		wrapscan_start, wrapscan_scan, wrapscan_stop, 
-		&wrapscan, NULL ) );
-}
-
-/* Start function: allocate space for a double in which we can accumulate the
- * sum.
- */
-static void *
-avg_start( IMAGE *out, void *a, void *b )
-{
-	double *sum;
-
-	if( !(sum = IM_NEW( NULL, double )) ) 
-		return( NULL );
-	*sum = 0.0;
-
-	return( (void *) sum );
-}
-
-/* Stop function. Add this little sum to the main sum.
- */
-static int
-avg_stop( void *seq, void *a, void *b )
-{
-	double *sum = (double *) seq;
-	double *global_sum = (double *) b;
-
-	*global_sum += *sum;
-
-	im_free( seq );
-
-	return( 0 );
-}
-
-/* Sum pels in this section.
- */
-#define LOOP( TYPE ) { \
-	TYPE *p = (TYPE *) in; \
-	\
-	for( x = 0; x < sz; x++ ) \
-		m += p[x]; \
-}
-
-#define CLOOP( TYPE ) { \
-	TYPE *p = (TYPE *) in; \
-	\
-	for( x = 0; x < sz; x++ ) { \
-		double mod, re, im; \
-		\
-		re = p[0]; \
-		im = p[1]; \
-		p += 2; \
-		mod = re * re + im * im; \
-		\
-		m += mod; \
-	} \
-} 
-
-/* Loop over region, accumulating a sum in *tmp.
- */
-static int
-avg_scan( void *in, int n, void *seq, void *a, void *b )
-{
-	const IMAGE *im = (IMAGE *) a;
-	const int sz = n * im->Bands;
-
-	double *sum = (double *) seq;
-
-	int x;
-	double m;
-
-	m = *sum;
-
-	/* Now generate code for all types. 
-	 */
-	switch( im->BandFmt ) {
-	case IM_BANDFMT_UCHAR:		LOOP( unsigned char ); break; 
-	case IM_BANDFMT_CHAR:		LOOP( signed char ); break; 
-	case IM_BANDFMT_USHORT:		LOOP( unsigned short ); break; 
-	case IM_BANDFMT_SHORT:		LOOP( signed short ); break; 
-	case IM_BANDFMT_UINT:		LOOP( unsigned int ); break;
-	case IM_BANDFMT_INT:		LOOP( signed int ); 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; 
-
-	default: 
-		g_assert( 0 );
-	}
-
-	*sum = m;
-
-	return( 0 );
-}
-
-/**
- * im_avg:
- * @in: input #IMAGE
- * @out: output pixel average
- *
- * This operation finds the average value in an image. It operates on all 
- * bands of the input image: use im_stats() if you need to calculate an 
- * average for each band. For complex images, return the average modulus.
- *
- * See also: im_stats(), im_bandmean(), im_deviate(), im_rank()
- *
- * Returns: 0 on success, -1 on error
- */
-int
-im_avg( IMAGE *in, double *out )
-{
-	double global_sum;
-	gint64 vals, pels;
-
-	/* Check our args. 
-	 */
-	if( im_pincheck( in ) ||
-		im_check_noncomplex( "im_avg", in ) ||
-		im_check_uncoded( "im_avg", in ) ) 
-		return( -1 );
-
-	/* Loop over input, summing pixels.
-	 */
-	global_sum = 0.0;
-	if( im__wrapscan( in, 
-		avg_start, avg_scan, avg_stop, in, &global_sum ) ) 
-		return( -1 );
-
-	/* Calculate and return average. For complex, we accumulate re*re +
-	 * im*im, so we need to sqrt.
-	 */
-	pels = (gint64) in->Xsize * in->Ysize;
-	vals = pels * in->Bands;
-	*out = global_sum / vals;
-	if( vips_bandfmt_iscomplex( in->BandFmt ) )
-		*out = sqrt( *out );
-
-	return( 0 );
-}
-
-/* Get the value of pixel (0, 0). Use this to init the min/max value for
- * im_max()/im_stats()/etc. 
- */
-int
-im__value( IMAGE *im, double *value )
-{
-	IMAGE *t;
-
-	if( !(t = im_open_local( im, "im__value", "p" )) ||
-		im_extract_areabands( im, t, 0, 0, 1, 1, 0, 1 ) ||
-		im_avg( t, value ) )
-		return( -1 );
-
-	return( 0 );
-}

libvips/arithmetic/im_deviate.c

@@ -73,6 +73,74 @@
 #include <dmalloc.h>
 #endif /*WITH_DMALLOC*/
 
+typedef struct _Wrapscan {
+	IMAGE *in;
+	im_start_fn start; 
+	im__wrapscan_fn scan; 
+	im_stop_fn stop;
+	void *a; 
+	void *b;
+} Wrapscan;
+
+static void *
+wrapscan_start( VipsImage *in, void *a, void *b )
+{
+	Wrapscan *wrapscan = (Wrapscan *) a;
+
+	return( wrapscan->start( in, wrapscan->a, wrapscan->b ) );
+}
+
+static int
+wrapscan_stop( void *seq, void *a, void *b )
+{
+	Wrapscan *wrapscan = (Wrapscan *) a;
+
+	return( wrapscan->stop( seq, wrapscan->a, wrapscan->b ) );
+}
+
+static int
+wrapscan_scan( REGION *reg, void *seq, void *a, void *b )
+{
+	Wrapscan *wrapscan = (Wrapscan *) a;
+	Rect *r = &reg->valid;
+	int lsk = IM_REGION_LSKIP( reg );
+
+	int y;
+	PEL *p;
+
+	p = (PEL *) IM_REGION_ADDR( reg, r->left, r->top ); 
+	for( y = 0; y < r->height; y++ ) { 
+		if( wrapscan->scan( p, r->width, seq, 
+			wrapscan->a, wrapscan->b ) )
+			return( -1 );
+		p += lsk;
+	} 
+
+	return( 0 );
+}
+
+/* Like vips_sink(), but the scan function works a line at a time, like
+ * im_wrap*(). Shared with im_min(), im_deviate() etc.
+ */
+int
+im__wrapscan( VipsImage *in, 
+	VipsStart start, im__wrapscan_fn scan, VipsStop stop,
+	void *a, void *b )
+{
+	Wrapscan wrapscan;
+
+	wrapscan.in = in;
+	wrapscan.start = start;
+	wrapscan.scan = scan;
+	wrapscan.stop = stop;
+	wrapscan.a = a;
+	wrapscan.b = b;
+
+	return( vips_sink( in, 
+		wrapscan_start, wrapscan_scan, wrapscan_stop, 
+		&wrapscan, NULL ) );
+}
+
 /* Start function: allocate space for a pair of doubles in which we can 
  * accumulate the sum and the sum of squares.
  */

libvips/arithmetic/im_maxpos.c

@@ -63,6 +63,22 @@
 #include <dmalloc.h>
 #endif /*WITH_DMALLOC*/
 
+/* Get the value of pixel (0, 0). Use this to init the min/max value for
+ * im_max()/im_stats()/etc. 
+ */
+int
+im__value( IMAGE *im, double *value )
+{
+	IMAGE *t;
+
+	if( !(t = im_open_local( im, "im__value", "p" )) ||
+		im_extract_areabands( im, t, 0, 0, 1, 1, 0, 1 ) ||
+		im_avg( t, value ) )
+		return( -1 );
+
+	return( 0 );
+}
+
 /* A position and maximum.
  */
 typedef struct _Maxpos {

libvips/arithmetic/statistic.c

@@ -0,0 +1,166 @@
+/* base class for all stats operations
+ *
+ * properties:
+ * 	- one image in, single value or matrix out
+ * 	- output depends on whole of input, ie. we have a sink
+ *
+ * 24/8/11
+ * 	- from im_avg.c
+ */
+
+/*
+
+    Copyright (C) 1991-2005 The National Gallery
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+ */
+
+/*
+
+    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
+
+ */
+
+/*
+#define DEBUG
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif /*HAVE_CONFIG_H*/
+#include <vips/intl.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include <vips/vips.h>
+
+#include "statistic.h"
+
+#ifdef WITH_DMALLOC
+#include <dmalloc.h>
+#endif /*WITH_DMALLOC*/
+
+/* Properties.
+ */
+enum {
+	PROP_INPUT = 1,
+	PROP_LAST
+}; 
+
+G_DEFINE_ABSTRACT_TYPE( VipsStatistic, vips_statistic, VIPS_TYPE_OPERATION );
+
+static void *
+vips_statistic_scan_start( VipsImage *in, void *a, void *b )
+{
+	VipsStatistic *statistic = VIPS_STATISTIC( a );
+	VipsStatisticClass *class = VIPS_STATISTIC_GET_CLASS( statistic );
+
+	return( class->start( statistic ) );
+}
+
+static int
+vips_statistic_scan( VipsRegion *region, void *seq, void *a, void *b )
+{
+	VipsStatistic *statistic = VIPS_STATISTIC( a );
+	VipsStatisticClass *class = VIPS_STATISTIC_GET_CLASS( statistic );
+
+	VipsRect *r = &region->valid;
+	int lsk = IM_REGION_LSKIP( region );
+
+	int y;
+	PEL *p;
+
+	p = (PEL *) IM_REGION_ADDR( region, r->left, r->top ); 
+	for( y = 0; y < r->height; y++ ) { 
+		if( class->scan( statistic, seq, p, r->width ) ) 
+			return( -1 );
+		p += lsk;
+	} 
+
+	return( 0 );
+}
+
+static int
+vips_statistic_scan_stop( void *seq, void *a, void *b )
+{
+	VipsStatistic *statistic = VIPS_STATISTIC( a );
+	VipsStatisticClass *class = VIPS_STATISTIC_GET_CLASS( statistic );
+
+	return( class->stop( statistic, seq ) );
+}
+
+static int
+vips_statistic_build( VipsObject *object )
+{
+	VipsStatistic *statistic = VIPS_STATISTIC( object );
+	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
+	const char *domain = class->nickname;
+
+#ifdef DEBUG
+	printf( "vips_statistic_build: " );
+	vips_object_print_name( object );
+	printf( "\n" );
+#endif /*DEBUG*/
+
+	if( VIPS_OBJECT_CLASS( vips_statistic_parent_class )->build( object ) )
+		return( -1 );
+
+	if( vips_image_pio_input( statistic->input ) || 
+		vips_check_uncoded( domain, statistic->input ) )
+		return( -1 );
+
+	if( vips_sink( statistic->input, 
+		vips_statistic_scan_start, 
+		vips_statistic_scan, 
+		vips_statistic_scan_stop, 
+		statistic, NULL ) )
+		return( -1 );
+
+	return( 0 );
+}
+
+static void
+vips_statistic_class_init( VipsStatisticClass *class )
+{
+	GObjectClass *gobject_class = G_OBJECT_CLASS( class );
+	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
+
+	GParamSpec *pspec;
+
+	gobject_class->set_property = vips_object_set_property;
+	gobject_class->get_property = vips_object_get_property;
+
+	vobject_class->nickname = "statistic";
+	vobject_class->description = _( "VIPS statistic operations" );
+	vobject_class->build = vips_statistic_build;
+
+	pspec = g_param_spec_object( "in", "Input", 
+		_( "Input image" ),
+		VIPS_TYPE_IMAGE,
+		G_PARAM_READWRITE );
+	g_object_class_install_property( gobject_class, 
+		PROP_INPUT, pspec );
+	vips_object_class_install_argument( vobject_class, pspec,
+		VIPS_ARGUMENT_REQUIRED_INPUT, 
+		G_STRUCT_OFFSET( VipsStatistic, input ) );
+}
+
+static void
+vips_statistic_init( VipsStatistic *statistic )
+{
+}

libvips/arithmetic/statistic.h

@@ -0,0 +1,91 @@
+/* base class for all stats operations
+ */
+
+/*
+
+    Copyright (C) 1991-2005 The National Gallery
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+ */
+
+/*
+
+    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
+
+ */
+
+#ifndef VIPS_STATISTIC_H
+#define VIPS_STATISTIC_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif /*__cplusplus*/
+
+#include <vips/vector.h>
+
+#define VIPS_TYPE_STATISTIC (vips_statistic_get_type())
+#define VIPS_STATISTIC( obj ) \
+	(G_TYPE_CHECK_INSTANCE_CAST( (obj), \
+		VIPS_TYPE_STATISTIC, VipsStatistic ))
+#define VIPS_STATISTIC_CLASS( klass ) \
+	(G_TYPE_CHECK_CLASS_CAST( (klass), \
+		VIPS_TYPE_STATISTIC, VipsStatisticClass))
+#define VIPS_IS_STATISTIC( obj ) \
+	(G_TYPE_CHECK_INSTANCE_TYPE( (obj), VIPS_TYPE_STATISTIC ))
+#define VIPS_IS_STATISTIC_CLASS( klass ) \
+	(G_TYPE_CHECK_CLASS_TYPE( (klass), VIPS_TYPE_STATISTIC ))
+#define VIPS_STATISTIC_GET_CLASS( obj ) \
+	(G_TYPE_INSTANCE_GET_CLASS( (obj), \
+		VIPS_TYPE_STATISTIC, VipsStatisticClass ))
+
+typedef struct _VipsStatistic VipsStatistic;
+typedef struct _VipsStatisticClass VipsStatisticClass;
+
+typedef void *(*VipsStatisticStartFn)( VipsStatistic *statistic ); 
+typedef int (*VipsStatisticScanFn)( VipsStatistic *statistic, void *seq,
+	void *p, int n );  
+typedef int (*VipsStatisticStopFn)( VipsStatistic *statistic, void *seq );
+
+struct _VipsStatistic {
+	VipsOperation parent_instance;
+
+	/* All have an input image.
+	 */
+	VipsImage *input;
+
+	/* Client data for the subclass.
+	 */
+	void *a; 
+	void *b;
+};
+
+struct _VipsStatisticClass {
+	VipsOperationClass parent_class;
+
+	/* Start/scan/stop, for vips_sink.
+	 */
+	VipsStatisticStartFn start; 
+	VipsStatisticScanFn scan; 
+	VipsStatisticStopFn stop;
+};
+
+GType vips_statistic_get_type( void );
+
+#ifdef __cplusplus
+}
+#endif /*__cplusplus*/
+
+#endif /*VIPS_STATISTIC_H*/

libvips/arithmetic/subtract.c

@@ -186,29 +186,30 @@ subtract_buffer( VipsBinary *binary,
 
 	/* Complex just doubles the size.
 	 */
-	const int sz = width * im->Bands * 
+	const int sz = width * vips_image_get_bands( im ) * 
-		(vips_band_format_iscomplex( im->BandFmt ) ? 2 : 1);
+		(vips_band_format_iscomplex( vips_image_get_format( im ) ) ? 
+		 	2 : 1);
 
 	int x;
 
 	/* Keep types here in sync with bandfmt_subtract[] 
 	 * below.
          */
-        switch( im->BandFmt ) {
+        switch( vips_image_get_format( im ) ) {
-        case IM_BANDFMT_CHAR: 	LOOP( signed char, signed short ); break; 
+        case VIPS_FORMAT_CHAR: 	LOOP( signed char, signed short ); break; 
-        case IM_BANDFMT_UCHAR: 	LOOP( unsigned char, signed short ); break; 
+        case VIPS_FORMAT_UCHAR:	LOOP( unsigned char, signed short ); break; 
-        case IM_BANDFMT_SHORT: 	LOOP( signed short, signed int ); break; 
+        case VIPS_FORMAT_SHORT:	LOOP( signed short, signed int ); break; 
-        case IM_BANDFMT_USHORT: LOOP( unsigned short, signed int ); break; 
+        case VIPS_FORMAT_USHORT:LOOP( unsigned short, signed int ); break; 
-        case IM_BANDFMT_INT: 	LOOP( signed int, signed int ); break; 
+        case VIPS_FORMAT_INT: 	LOOP( signed int, signed int ); break; 
-        case IM_BANDFMT_UINT: 	LOOP( unsigned int, signed int ); break; 
+        case VIPS_FORMAT_UINT: 	LOOP( unsigned int, signed int ); break; 
 
-        case IM_BANDFMT_FLOAT: 		
+        case VIPS_FORMAT_FLOAT: 		
-        case IM_BANDFMT_COMPLEX:
+        case VIPS_FORMAT_COMPLEX:
 		LOOP( float, float ); 
 		break; 
 
-        case IM_BANDFMT_DOUBLE:	
+        case VIPS_FORMAT_DOUBLE:	
-        case IM_BANDFMT_DPCOMPLEX:
+        case VIPS_FORMAT_DPCOMPLEX:
 		LOOP( double, double ); 
 		break;
 
@@ -219,21 +220,21 @@ subtract_buffer( VipsBinary *binary,
 
 /* Save a bit of typing.
  */
-#define UC IM_BANDFMT_UCHAR
+#define UC VIPS_FORMAT_UCHAR
-#define C IM_BANDFMT_CHAR
+#define C VIPS_FORMAT_CHAR
-#define US IM_BANDFMT_USHORT
+#define US VIPS_FORMAT_USHORT
-#define S IM_BANDFMT_SHORT
+#define S VIPS_FORMAT_SHORT
-#define UI IM_BANDFMT_UINT
+#define UI VIPS_FORMAT_UINT
-#define I IM_BANDFMT_INT
+#define I VIPS_FORMAT_INT
-#define F IM_BANDFMT_FLOAT
+#define F VIPS_FORMAT_FLOAT
-#define X IM_BANDFMT_COMPLEX
+#define X VIPS_FORMAT_COMPLEX
-#define D IM_BANDFMT_DOUBLE
+#define D VIPS_FORMAT_DOUBLE
-#define DX IM_BANDFMT_DPCOMPLEX
+#define DX VIPS_FORMAT_DPCOMPLEX
 
 /* Type promotion for subtraction. Sign and value preserving. Make sure these
  * match the case statement in subtract_buffer() above.
  */
-static int bandfmt_subtract[10] = {
+static const VipsBandFormat bandfmt_subtract[10] = {
 /* UC  C   US  S   UI  I  F  X  D  DX */
    S,  S,  I,  I,  I,  I, F, X, D, DX
 };

libvips/deprecated/vips7compat.c

@@ -948,3 +948,9 @@ im_subtract( IMAGE *in1, IMAGE *in2, IMAGE *out )
 
 	return( 0 );
 }
+
+int
+im_avg( IMAGE *in, double *out )
+{
+	return( vips_avg( in, out, NULL ) ); 
+}

libvips/include/vips/arithmetic.h

@@ -37,8 +37,13 @@
 extern "C" {
 #endif /*__cplusplus*/
 
-/* arithmetic
+VipsImage *vips_add( VipsImage *in1, VipsImage *in2, ... );
- */
+VipsImage *vips_subtract( VipsImage *in1, VipsImage *in2, ... );
+int vips_avg( VipsImage *in, double *out, ... );
+
+
+
+
 DOUBLEMASK *im_measure_area( VipsImage *im, 
 	int left, int top, int width, int height, 
 	int h, int v, 
@@ -55,8 +60,6 @@ int im_maxpos_vec( VipsImage *im, int *xpos, int *ypos, double *maxima, int n );
 int im_minpos_vec( VipsImage *im, int *xpos, int *ypos, double *minima, int n );
 int im_bandmean( VipsImage *in, VipsImage *out );
 
-int im_add( VipsImage *in1, VipsImage *in2, VipsImage *out );
-int im_subtract( VipsImage *in1, VipsImage *in2, VipsImage *out );
 int im_invert( VipsImage *in, VipsImage *out );
 int im_lintra( double a, VipsImage *in, double b, VipsImage *out );
 int im_lintra_vec( int n, double *a, VipsImage *in, double *b, VipsImage *out );

libvips/include/vips/header.h

@@ -72,18 +72,18 @@ extern "C" {
 
 int vips_format_sizeof( VipsBandFormat format );
 
-int vips_image_get_width( VipsImage *image );
+int vips_image_get_width( const VipsImage *image );
-int vips_image_get_height( VipsImage *image );
+int vips_image_get_height( const VipsImage *image );
-int vips_image_get_bands( VipsImage *image );
+int vips_image_get_bands( const VipsImage *image );
-VipsBandFormat vips_image_get_format( VipsImage *image );
+VipsBandFormat vips_image_get_format( const VipsImage *image );
-VipsCoding vips_image_get_coding( VipsImage *image );
+VipsCoding vips_image_get_coding( const VipsImage *image );
-VipsInterpretation vips_image_get_interpretation( VipsImage *image );
+VipsInterpretation vips_image_get_interpretation( const VipsImage *image );
-double vips_image_get_xres( VipsImage *image );
+double vips_image_get_xres( const VipsImage *image );
-double vips_image_get_yres( VipsImage *image );
+double vips_image_get_yres( const VipsImage *image );
-int vips_image_get_xoffset( VipsImage *image );
+int vips_image_get_xoffset( const VipsImage *image );
-int vips_image_get_yoffset( VipsImage *image );
+int vips_image_get_yoffset( const VipsImage *image );
-const char *vips_image_get_filename( VipsImage *image );
+const char *vips_image_get_filename( const VipsImage *image );
-const char *vips_image_get_mode( VipsImage *image );
+const char *vips_image_get_mode( const VipsImage *image );
 void *vips_image_get_data( VipsImage *image );;
 
 void vips_image_init_fields( VipsImage *image, 
@@ -99,6 +99,7 @@ int vips_image_copy_fields( VipsImage *out, VipsImage *in );
 
 int vips_image_set( VipsImage *image, const char *field, GValue *value );
 int vips_image_get( VipsImage *image, const char *field, GValue *value_copy );
+int vips_image_get_as_string( VipsImage *image, const char *field, char **out );
 GType vips_image_get_typeof( VipsImage *image, const char *field );
 gboolean vips_image_remove( VipsImage *image, const char *field );
 typedef void *(*VipsImageMapFn)( VipsImage *image, 
@@ -170,8 +171,6 @@ int vips_image_set_double( VipsImage *image, const char *field, double d );
 int vips_image_get_string( VipsImage *image, const char *field, char **out );
 int vips_image_set_string( VipsImage *image, 
 	const char *field, const char *str );
-int vips_image_get_as_string( VipsImage *image, const char *field, char **out );
-GType vips_image_get_typeof( VipsImage *image, const char *field );
 
 int vips_image_history_printf( VipsImage *image, const char *format, ... )
 	__attribute__((format(printf, 2, 3)));

libvips/include/vips/vips7compat.h

@@ -486,6 +486,9 @@ int im_wrapmany( VipsImage **in, VipsImage *out,
 #define im_concurrency_set vips_concurrency_set
 #define im_concurrency_get vips_concurrency_get
 
+int im_add( VipsImage *in1, VipsImage *in2, VipsImage *out );
+int im_subtract( VipsImage *in1, VipsImage *in2, VipsImage *out );
+
 #ifdef __cplusplus
 }
 #endif /*__cplusplus*/

libvips/iofuncs/header.c

@@ -343,73 +343,73 @@ meta_init( VipsImage *im )
 }
 
 int
-vips_image_get_width( VipsImage *image )
+vips_image_get_width( const VipsImage *image )
 {
 	return( image->Xsize );
 }
 
 int
-vips_image_get_height( VipsImage *image )
+vips_image_get_height( const VipsImage *image )
 {
 	return( image->Ysize );
 }
 
 int
-vips_image_get_bands( VipsImage *image )
+vips_image_get_bands( const VipsImage *image )
 {
 	return( image->Bands );
 }
 
 VipsBandFormat
-vips_image_get_format( VipsImage *image )
+vips_image_get_format( const VipsImage *image )
 {
 	return( image->BandFmt );
 }
 
 VipsCoding
-vips_image_get_coding( VipsImage *image )
+vips_image_get_coding( const VipsImage *image )
 {
 	return( image->Coding );
 }
 
 VipsInterpretation
-vips_image_get_interpretation( VipsImage *image )
+vips_image_get_interpretation( const VipsImage *image )
 {
 	return( image->Type );
 }
 
 double
-vips_image_get_xres( VipsImage *image )
+vips_image_get_xres( const VipsImage *image )
 {
 	return( image->Xres );
 }
 
 double
-vips_image_get_yres( VipsImage *image )
+vips_image_get_yres( const VipsImage *image )
 {
 	return( image->Yres );
 }
 
 int
-vips_image_get_xoffset( VipsImage *image )
+vips_image_get_xoffset( const VipsImage *image )
 {
 	return( image->Xoffset );
 }
 
 int
-vips_image_get_yoffset( VipsImage *image )
+vips_image_get_yoffset( const VipsImage *image )
 {
 	return( image->Yoffset );
 }
 
 const char *
-vips_image_get_filename( VipsImage *image )
+vips_image_get_filename( const VipsImage *image )
 {
 	return( image->filename );
 }
 
 const char *
-vips_image_get_mode( VipsImage *image )
+vips_image_get_mode( const VipsImage *image )
 {
 	return( image->mode );
 }

libvips/iofuncs/object.c

@@ -125,18 +125,66 @@ vips_object_postclose( VipsObject *object )
 	}
 }
 
+static void *
+vips_object_check_required( VipsObject *object, GParamSpec *pspec,
+	VipsArgumentClass *argument_class,
+	VipsArgumentInstance *argument_instance,
+	void *a, void *b )
+{
+	int *result = (int *) a;
+
+	VIPS_DEBUG_MSG( "vips_object_check_required: %s\n", 
+		g_param_spec_get_name( pspec ) );
+	VIPS_DEBUG_MSG( "\trequired: %d\n", 
+		argument_class->flags & VIPS_ARGUMENT_REQUIRED );
+	VIPS_DEBUG_MSG( "\tconstruct: %d\n", 
+		argument_class->flags & VIPS_ARGUMENT_CONSTRUCT ); 
+	VIPS_DEBUG_MSG( "\tassigned: %d\n", 
+		argument_instance->assigned );
+
+	if( (argument_class->flags & VIPS_ARGUMENT_REQUIRED) &&
+		(argument_class->flags & VIPS_ARGUMENT_CONSTRUCT) &&
+		!argument_instance->assigned ) {
+		vips_error( "VipsObject",
+			/* used as eg. "parameter out to VipsAdd not set".
+			 */
+			_( "parameter %s to %s not set" ),
+			g_param_spec_get_name( pspec ),
+			G_OBJECT_TYPE_NAME( object ) );
+		*result = -1;
+	}
+
+	return( NULL );
+}
+
 int
 vips_object_build( VipsObject *object )
 {
 	VipsObjectClass *object_class = VIPS_OBJECT_GET_CLASS( object );
 
+	int result;
+
 #ifdef DEBUG
 	printf( "vips_object_build: " );
 	vips_object_print_name( object );
 	printf( "\n" );
 #endif /*DEBUG*/
 
-	return( object_class->build( object ) );
+	if( object_class->build( object ) )
+		return( -1 );
+
+	/* Check all required arguments have been supplied, don't stop on 1st
+	 * error.
+	 */
+	result = 0;
+	(void) vips_argument_map( object,
+		vips_object_check_required, &result, NULL );
+
+	/* ... more checks go here.
+	 */
+	object->constructed = TRUE;
+
+	return( result );
 }
 
 void
@@ -840,45 +888,11 @@ vips_object_get_property( GObject *gobject,
 	}
 }
 
-static void *
-vips_object_check_required( VipsObject *object, GParamSpec *pspec,
-	VipsArgumentClass *argument_class,
-	VipsArgumentInstance *argument_instance,
-	void *a, void *b )
-{
-	int *result = (int *) a;
-
-	VIPS_DEBUG_MSG( "vips_object_check_required: %s\n", 
-		g_param_spec_get_name( pspec ) );
-	VIPS_DEBUG_MSG( "\trequired: %d\n", 
-		argument_class->flags & VIPS_ARGUMENT_REQUIRED );
-	VIPS_DEBUG_MSG( "\tconstruct: %d\n", 
-		argument_class->flags & VIPS_ARGUMENT_CONSTRUCT ); 
-	VIPS_DEBUG_MSG( "\tassigned: %d\n", 
-		argument_instance->assigned );
-
-	if( (argument_class->flags & VIPS_ARGUMENT_REQUIRED) &&
-		(argument_class->flags & VIPS_ARGUMENT_CONSTRUCT) &&
-		!argument_instance->assigned ) {
-		vips_error( "VipsObject",
-			/* used as eg. "parameter out to VipsAdd not set".
-			 */
-			_( "parameter %s to %s not set" ),
-			g_param_spec_get_name( pspec ),
-			G_OBJECT_TYPE_NAME( object ) );
-		*result = -1;
-	}
-
-	return( NULL );
-}
-
 static int
 vips_object_real_build( VipsObject *object )
 {
 	VipsObjectClass *object_class = VIPS_OBJECT_GET_CLASS( object );
 
-	int result;
-
 #ifdef DEBUG
 	printf( "vips_object_real_build: " ); 
 	vips_object_print_name( object );
@@ -887,17 +901,6 @@ vips_object_real_build( VipsObject *object )
 
 	g_assert( !object->constructed );
 
-	/* Check all required arguments have been supplied, don't stop on 1st
-	 * error.
-	 */
-	result = 0;
-	(void) vips_argument_map( object,
-		vips_object_check_required, &result, NULL );
-
-	/* ... more checks go here.
-	 */
-	object->constructed = TRUE;
-
 	/* It'd be nice if this just copied a pointer rather than did a
 	 * strdup(). Set these here rather than in object_init, so that the
 	 * class gets a chance to set them.
@@ -906,7 +909,14 @@ vips_object_real_build( VipsObject *object )
 		"nickname", object_class->nickname,
 		"description", object_class->description, NULL );
 
-	return( result );
+	/* We can't check that all required args have been set here, since our
+	 * superclasses' build funcs might want to set some one the way out,
+	 * see VipsAvg, for example.
+	 *
+	 * Do these checks in the build dispatch function, see above.
+	 */
+
+	return( 0 );
 }
 
 static void
@@ -1286,7 +1296,7 @@ vips_object_get_argument_to_string( VipsObject *object,
 		VipsBuf buf = VIPS_BUF_STATIC( str );
 
 		vips_object_print_arg( object, pspec, &buf );
-		printf( "%s", vips_buf_all( &buf ) );
+		printf( "%s\n", vips_buf_all( &buf ) );
 	}
 
 	return( 0 );