diff --git a/ChangeLog b/ChangeLog
index 57a569df..abef4d30 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,7 +3,8 @@
 - rename image arrays as image matrices ... INTERPRETATION_ARRAY ->
   INTERPRETATION_MATRIX etc. 
 - rewrite im_buildlut(), im_identity*(), im_maplut(), im_falsecolour(),
-  im_gammacorrect(), im_histgr() as classes
+  im_gammacorrect(), im_histgr(), im_histcum(), im_histnorm(), im_heq() 
+  as classes
 - added vips_error_freeze() / vips_error_thaw()
 - used freeze() / thaw() to stop file format sniffers logging spurious errors
 - vipsthumbnail uses embedded jpg thumbnails if it can 
diff --git a/libvips/deprecated/vips7compat.c b/libvips/deprecated/vips7compat.c
index 71c8ed94..a3387cce 100644
--- a/libvips/deprecated/vips7compat.c
+++ b/libvips/deprecated/vips7compat.c
@@ -3324,6 +3324,70 @@ im_maplut( IMAGE *in, IMAGE *out, IMAGE *lut )
 	return( 0 );
 }
 
+int 
+im_histcum( IMAGE *in, IMAGE *out )
+{
+	VipsImage *x;
+
+	if( vips_hist_cum( in, &x, NULL ) )
+		return( -1 );
+
+	if( im_copy( x, out ) ) {
+		g_object_unref( x );
+		return( -1 );
+	}
+	g_object_unref( x );
+
+	return( 0 );
+}
+
+int 
+im_histnorm( IMAGE *in, IMAGE *out )
+{
+	VipsImage *x;
+
+	if( vips_hist_norm( in, &x, NULL ) )
+		return( -1 );
+
+	if( im_copy( x, out ) ) {
+		g_object_unref( x );
+		return( -1 );
+	}
+	g_object_unref( x );
+
+	return( 0 );
+}
+
+int 
+im_histeq( IMAGE *in, IMAGE *out )
+{
+	IMAGE *t1;
+
+	if( !(t1 = im_open_local( out, "im_histeq", "p" )) ||
+		im_histcum( in, t1 ) || 
+		im_histnorm( t1, out ) )
+		return( -1 );
+
+	return( 0 );
+}
+
+int 
+im_heq( VipsImage *in, VipsImage *out, int bandno )
+{
+	VipsImage *x;
+
+	if( vips_hist_equal( in, &x, "band", bandno, NULL ) )
+		return( -1 );
+
+	if( im_copy( x, out ) ) {
+		g_object_unref( x );
+		return( -1 );
+	}
+	g_object_unref( x );
+
+	return( 0 ); 
+}
+
 int 
 im_hist( IMAGE *in, IMAGE *out, int bandno )
 {
diff --git a/libvips/histogram/Makefile.am b/libvips/histogram/Makefile.am
index a3c3b929..e41ac1d8 100644
--- a/libvips/histogram/Makefile.am
+++ b/libvips/histogram/Makefile.am
@@ -1,12 +1,16 @@
 noinst_LTLIBRARIES = libhistogram.la
 
 libhistogram_la_SOURCES = \
-	maplut.c \
 	histogram.c \
 	phistogram.h \
+	maplut.c \
+	hist_buffer.c \
+	hist_buffer.h \
+	hist_cum.c \
+	hist_norm.c \
+	hist_equal.c \
+	\
 	hist_dispatch.c \
-	im_heq.c \
-	im_histeq.c \
 	im_histnD.c \
 	im_histplot.c \
 	im_histindexed.c \
diff --git a/libvips/histogram/hist_buffer.c b/libvips/histogram/hist_buffer.c
new file mode 100644
index 00000000..5a59f958
--- /dev/null
+++ b/libvips/histogram/hist_buffer.c
@@ -0,0 +1,117 @@
+/* a hist operation implemented as a buffer processor
+ *
+ * properties:
+ * 	- single hist to single hist
+ */
+
+/*
+
+    Copyright (C) 1991-2005 The National Gallery
+
+    This library 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 2.1 of the License, or (at your option) any later version.
+
+    This library 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 library; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+    02110-1301  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 <vips/internal.h>
+
+#include "phistogram.h"
+#include "hist_buffer.h"
+
+G_DEFINE_ABSTRACT_TYPE( VipsHistBuffer, vips_hist_buffer, VIPS_TYPE_HISTOGRAM );
+
+static int
+vips_hist_buffer_build( VipsObject *object )
+{
+	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
+	VipsHistogram *histogram = VIPS_HISTOGRAM( object );
+	VipsHistBuffer *hist_buffer = VIPS_HIST_BUFFER( object );
+	VipsHistBufferClass *hclass = VIPS_HIST_BUFFER_GET_CLASS( hist_buffer );
+
+	VipsPel *outbuf;		
+
+#ifdef DEBUG
+	printf( "vips_hist_buffer_build: " );
+	vips_object_print_name( object );
+	printf( "\n" );
+#endif /*DEBUG*/
+
+	if( VIPS_OBJECT_CLASS( vips_hist_buffer_parent_class )->
+		build( object ) )
+		return( -1 );
+
+	if( vips_check_hist( class->nickname, histogram->in ) ||
+		vips_check_uncoded( class->nickname, histogram->in ) )
+		return( -1 ); 
+
+	if( vips_image_wio_input( histogram->in ) ||
+		vips_image_copy_fields( histogram->out, histogram->in ) ) 
+		return( -1 );
+
+	histogram->out->Xsize = VIPS_IMAGE_N_PELS( histogram->in );
+	histogram->out->Ysize = 1;
+	if( hclass->format_table ) 
+		histogram->out->BandFmt = 
+			hclass->format_table[histogram->in->BandFmt];
+
+	if( !(outbuf = vips_malloc( object, 
+		VIPS_IMAGE_SIZEOF_LINE( histogram->out ))) )
+                return( -1 );
+
+	hclass->process( hist_buffer, 
+		outbuf, VIPS_IMAGE_ADDR( histogram->in, 0, 0 ), 
+		histogram->in->Xsize );
+
+	if( vips_image_write_line( histogram->out, 0, outbuf ) )
+		return( -1 ); 
+
+	return( 0 );
+}
+
+static void
+vips_hist_buffer_class_init( VipsHistBufferClass *class )
+{
+	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
+
+	vobject_class->nickname = "hist_buffer";
+	vobject_class->description = _( "hist_buffer operations" );
+	vobject_class->build = vips_hist_buffer_build;
+
+}
+
+static void
+vips_hist_buffer_init( VipsHistBuffer *hist_buffer )
+{
+}
diff --git a/libvips/histogram/hist_buffer.h b/libvips/histogram/hist_buffer.h
new file mode 100644
index 00000000..80468ba1
--- /dev/null
+++ b/libvips/histogram/hist_buffer.h
@@ -0,0 +1,82 @@
+/* base class for all hist_buffer operations
+ */
+
+/*
+
+    Copyright (C) 1991-2005 The National Gallery
+
+    This library 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 2.1 of the License, or (at your option) any later version.
+
+    This library 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 library; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+    02110-1301  USA
+
+ */
+
+/*
+
+    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
+
+ */
+
+#ifndef VIPS_PHIST_BUFFER_H
+#define VIPS_PHIST_BUFFER_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif /*__cplusplus*/
+
+#include <vips/vector.h>
+
+#define VIPS_TYPE_HIST_BUFFER (vips_hist_buffer_get_type())
+#define VIPS_HIST_BUFFER( obj ) \
+	(G_TYPE_CHECK_INSTANCE_CAST( (obj), \
+		VIPS_TYPE_HIST_BUFFER, VipsHistBuffer ))
+#define VIPS_HIST_BUFFER_CLASS( klass ) \
+	(G_TYPE_CHECK_CLASS_CAST( (klass), \
+		VIPS_TYPE_HIST_BUFFER, VipsHistBufferClass))
+#define VIPS_IS_HIST_BUFFER( obj ) \
+	(G_TYPE_CHECK_INSTANCE_TYPE( (obj), VIPS_TYPE_HIST_BUFFER ))
+#define VIPS_IS_HIST_BUFFER_CLASS( klass ) \
+	(G_TYPE_CHECK_CLASS_TYPE( (klass), VIPS_TYPE_HIST_BUFFER ))
+#define VIPS_HIST_BUFFER_GET_CLASS( obj ) \
+	(G_TYPE_INSTANCE_GET_CLASS( (obj), \
+		VIPS_TYPE_HIST_BUFFER, VipsHistBufferClass ))
+
+struct _VipsHistBuffer;
+typedef void (*VipsHistBufferProcessFn)( struct _VipsHistBuffer *hist_buffer, 
+	VipsPel *out, VipsPel *in, int width );
+
+typedef struct _VipsHistBuffer {
+	VipsHistogram parent_instance;
+
+} VipsHistBuffer;
+
+typedef struct _VipsHistBufferClass {
+	VipsHistogramClass parent_class;
+
+	/* For each input format, what output format. 
+	 */
+	const VipsBandFormat *format_table;
+
+	VipsHistBufferProcessFn process;
+} VipsHistBufferClass;
+
+GType vips_hist_buffer_get_type( void );
+
+#ifdef __cplusplus
+}
+#endif /*__cplusplus*/
+
+#endif /*VIPS_PHIST_BUFFER_H*/
+
+
diff --git a/libvips/histogram/hist_cum.c b/libvips/histogram/hist_cum.c
index 87019aad..49d5e0b5 100644
--- a/libvips/histogram/hist_cum.c
+++ b/libvips/histogram/hist_cum.c
@@ -61,11 +61,17 @@
 #include <vips/vips.h>
 
 #include "phistogram.h"
+#include "hist_buffer.h"
+
+typedef VipsHistBuffer VipsHistCum;
+typedef VipsHistBufferClass VipsHistCumClass;
+
+G_DEFINE_TYPE( VipsHistCum, vips_hist_cum, VIPS_TYPE_HIST_BUFFER );
 
 #define ACCUMULATE( ITYPE, OTYPE ) { \
 	for( b = 0; b < nb; b++ ) { \
-		ITYPE *p = (ITYPE *) in->data; \
-		OTYPE *q = (OTYPE *) outbuf; \
+		ITYPE *p = (ITYPE *) in; \
+		OTYPE *q = (OTYPE *) out; \
 		OTYPE total; \
 		\
 		total = 0; \
@@ -76,74 +82,100 @@
 	} \
 }
 
-/**
- * im_histcum:
- * @in: input image
- * @out: output image
- *
- * Form cumulative histogram. 
- *
- * See also: im_histnorm().
- *
- * Returns: 0 on success, -1 on error
- */
-int 
-im_histcum( IMAGE *in, IMAGE *out )
+static void
+vips_hist_cum_buffer( VipsHistBuffer *hist_buffer, 
+	VipsPel *out, VipsPel *in, int width )
 {
-	const guint64 px = VIPS_IMAGE_N_PELS( in );
-	const int nb = vips_bandfmt_iscomplex( in->BandFmt ) ? 
-		in->Bands * 2 : in->Bands;
-	const guint64 mx = px * nb;
+	VipsHistogram *histogram = VIPS_HISTOGRAM( hist_buffer );
+	const int bands = vips_image_get_bands( histogram->in );
+	const int nb = vips_bandfmt_iscomplex( histogram->in->BandFmt ) ? 
+		bands * 2 : bands;
+	int mx = width * nb;
 
-	VipsPel *outbuf;		
-	guint64 b, x;
+	int x, b; 
 
-	if( im_check_uncoded( "im_histcum", in ) ||
-		im_check_hist( "im_histcum", in ) ||
-		im_iocheck( in, out ) )
-		return( -1 );
-
-	if( im_cp_desc( out, in ) )
-		return( -1 );
-	out->Xsize = px;
-	out->Ysize = 1;
-	if( vips_bandfmt_isuint( in->BandFmt ) )
-		out->BandFmt = IM_BANDFMT_UINT;
-	else if( vips_bandfmt_isint( in->BandFmt ) )
-		out->BandFmt = IM_BANDFMT_INT;
-	if( im_setupout( out ) )
-		return( -1 );
-
-	if( !(outbuf = im_malloc( out, IM_IMAGE_SIZEOF_LINE( out ))) )
-                return( -1 );
-
-        switch( in->BandFmt ) {
-        case IM_BANDFMT_CHAR: 		
+	switch( vips_image_get_format( histogram->in ) ) {
+        case VIPS_FORMAT_CHAR: 		
 		ACCUMULATE( signed char, signed int ); break; 
-        case IM_BANDFMT_UCHAR: 		
+        case VIPS_FORMAT_UCHAR: 		
 		ACCUMULATE( unsigned char, unsigned int ); break; 
-        case IM_BANDFMT_SHORT: 		
+        case VIPS_FORMAT_SHORT: 		
 		ACCUMULATE( signed short, signed int ); break; 
-        case IM_BANDFMT_USHORT: 	
+        case VIPS_FORMAT_USHORT: 	
 		ACCUMULATE( unsigned short, unsigned int ); break; 
-        case IM_BANDFMT_INT: 		
+        case VIPS_FORMAT_INT: 		
 		ACCUMULATE( signed int, signed int ); break; 
-        case IM_BANDFMT_UINT: 		
+        case VIPS_FORMAT_UINT: 		
 		ACCUMULATE( unsigned int, unsigned int ); break; 
 
-        case IM_BANDFMT_FLOAT: 		
-        case IM_BANDFMT_COMPLEX:	
+        case VIPS_FORMAT_FLOAT: 		
+        case VIPS_FORMAT_COMPLEX:	
 		ACCUMULATE( float, float ); break;
-        case IM_BANDFMT_DOUBLE:		
-        case IM_BANDFMT_DPCOMPLEX:	
+        case VIPS_FORMAT_DOUBLE:		
+        case VIPS_FORMAT_DPCOMPLEX:	
 		ACCUMULATE( double, double ); break;
 
         default:
 		g_assert( 0 );
         }
-
-	if( im_writeline( 0, out, outbuf ) )
-		return( -1 );
-
-	return( 0 );
+}
+
+/* Save a bit of typing.
+ */
+#define UC VIPS_FORMAT_UCHAR
+#define C VIPS_FORMAT_CHAR
+#define US VIPS_FORMAT_USHORT
+#define S VIPS_FORMAT_SHORT
+#define UI VIPS_FORMAT_UINT
+#define I VIPS_FORMAT_INT
+#define F VIPS_FORMAT_FLOAT
+#define X VIPS_FORMAT_COMPLEX
+#define D VIPS_FORMAT_DOUBLE
+#define DX VIPS_FORMAT_DPCOMPLEX
+
+static const VipsBandFormat vips_bandfmt_hist_cum[10] = {
+/* UC  C   US  S   UI  I   F   X   D   DX */
+   UI, I,  UI, I,  UI, I,  F,  F,  D,  D 
+};
+
+static void
+vips_hist_cum_class_init( VipsHistCumClass *class )
+{
+	VipsObjectClass *object_class = (VipsObjectClass *) class;
+	VipsHistBufferClass *hclass = VIPS_HIST_BUFFER_CLASS( class );
+
+	object_class->nickname = "hist_cum";
+	object_class->description = _( "form cumulative histogram" );
+
+	hclass->format_table = vips_bandfmt_hist_cum;
+	hclass->process = vips_hist_cum_buffer;
+}
+
+static void
+vips_hist_cum_init( VipsHistCum *hist_cum )
+{
+}
+
+/**
+ * vips_hist_cum:
+ * @in: input image
+ * @out: output image
+ *
+ * Form cumulative histogram. 
+ *
+ * See also: vips_hist_norm().
+ *
+ * Returns: 0 on success, -1 on error
+ */
+int 
+vips_hist_cum( VipsImage *in, VipsImage **out, ... )
+{
+	va_list ap;
+	int result;
+
+	va_start( ap, out );
+	result = vips_call_split( "hist_cum", ap, in, out );
+	va_end( ap );
+
+	return( result );
 }
diff --git a/libvips/histogram/hist_equal.c b/libvips/histogram/hist_equal.c
new file mode 100644
index 00000000..32efa294
--- /dev/null
+++ b/libvips/histogram/hist_equal.c
@@ -0,0 +1,146 @@
+/* Histogram-equalise an image.
+ *
+ * Copyright: 1991, N. Dessipris.
+ *
+ * Author: Nicos Dessipris
+ * Written on: 27/03/1991
+ * Modified on : 
+ * 16/6/93 J.Cupitt
+ *	- im_ioflag() changed to im_iocheck()
+ * 24/5/95 JC
+ *	- ANSIfied and tidied up
+ * 3/3/01 JC
+ *	- more cleanup
+ * 23/3/10
+ * 	- gtkdoc
+ * 12/8/13	
+ * 	- redone 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., 51 Franklin Street, Fifth Floor, Boston, MA
+    02110-1301  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 <vips/vips.h>
+
+#include "phistogram.h"
+
+typedef struct _VipsHistEqual { 
+	VipsHistogram parent_instance;
+
+	/* -1 for all bands, or the band we scan.
+	 */
+	int which;
+} VipsHistEqual;
+
+typedef VipsHistogramClass VipsHistEqualClass;
+
+G_DEFINE_TYPE( VipsHistEqual, vips_hist_equal, VIPS_TYPE_HISTOGRAM );
+
+static int
+vips_hist_equal_build( VipsObject *object )
+{
+	VipsHistogram *histogram = VIPS_HISTOGRAM( object );
+	VipsHistEqual *hist_equal = (VipsHistEqual *) histogram; 
+	VipsImage **t = (VipsImage **) vips_object_local_array( object, 4 );
+
+	if( VIPS_OBJECT_CLASS( vips_hist_equal_parent_class )->build( object ) )
+		return( -1 );
+
+	if( vips_hist_find( histogram->in, &t[0], 
+			"band", hist_equal->which,
+			NULL ) ||
+		vips_hist_cum( t[0], &t[1], NULL ) ||
+		vips_hist_norm( t[1], &t[2], NULL ) ||
+		vips_maplut( histogram->in, &t[3], t[2], NULL ) ||
+		vips_image_write( t[3], histogram->out ) )
+		return( -1 );
+
+	return( 0 );
+}
+
+static void
+vips_hist_equal_class_init( VipsHistEqualClass *class )
+{
+	GObjectClass *gobject_class = G_OBJECT_CLASS( class );
+	VipsObjectClass *object_class = (VipsObjectClass *) class;
+
+	gobject_class->set_property = vips_object_set_property;
+	gobject_class->get_property = vips_object_get_property;
+
+	object_class->nickname = "hist_equal";
+	object_class->description = _( "histogram equalisation" );
+	object_class->build = vips_hist_equal_build;
+
+	VIPS_ARG_INT( class, "band", 110, 
+		_( "Band" ), 
+		_( "Equalise with this band" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT, 
+		G_STRUCT_OFFSET( VipsHistEqual, which ),
+		-1, 100000, -1 );
+}
+
+static void
+vips_hist_equal_init( VipsHistEqual *hist_equal )
+{
+	hist_equal->which = -1;
+}
+
+/**
+ * vips_hist_equal:
+ * @in: input image
+ * @out: output image
+ *
+ * Optional arguments:
+ *
+ * @band: band to equalise
+ *
+ * Histogram-equalise @in. Equalise using band @bandno, or if @bandno is -1,
+ * equalise bands independently.
+ *
+ * See also: 
+ *
+ * Returns: 0 on success, -1 on error
+ */
+int 
+vips_hist_equal( VipsImage *in, VipsImage **out, ... )
+{
+	va_list ap;
+	int result;
+
+	va_start( ap, out );
+	result = vips_call_split( "hist_equal", ap, in, out );
+	va_end( ap );
+
+	return( result );
+}
diff --git a/libvips/histogram/hist_norm.c b/libvips/histogram/hist_norm.c
new file mode 100644
index 00000000..ac6e6177
--- /dev/null
+++ b/libvips/histogram/hist_norm.c
@@ -0,0 +1,159 @@
+/* histogram normalisation
+ *
+ * Author: N. Dessipris
+ * Written on: 02/08/1990
+ * 24/5/95 JC
+ *	- tidied up and ANSIfied
+ * 20/7/95 JC
+ *	- smartened up again
+ *	- now works for hists >256 elements
+ * 3/3/01 JC
+ *	- broken into norm and norm ... helps im_histspec()
+ *	- better behaviour for >8 bit hists
+ * 31/10/05 JC
+ * 	- was broken for vertical histograms, gah
+ * 	- neater im_histnorm()
+ * 23/7/07
+ * 	- eek, off by 1 for more than 1 band hists
+ * 12/5/08
+ * 	- histnorm works for signed hists now as well
+ * 24/3/10
+ * 	- gtkdoc
+ * 	- small cleanups
+ * 12/8/13	
+ * 	- redone im_histnorm() as a class, vips_hist_norm()
+ */
+
+/*
+
+    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., 51 Franklin Street, Fifth Floor, Boston, MA
+    02110-1301  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 <vips/vips.h>
+
+#include "phistogram.h"
+
+typedef VipsHistogram VipsHistNorm;
+typedef VipsHistogramClass VipsHistNormClass;
+
+G_DEFINE_TYPE( VipsHistNorm, vips_hist_norm, VIPS_TYPE_HISTOGRAM );
+
+static int
+vips_hist_norm_build( VipsObject *object )
+{
+	VipsHistogram *histogram = VIPS_HISTOGRAM( object );
+	VipsImage **t = (VipsImage **) vips_object_local_array( object, 3 );
+
+	guint64 px;
+	int bands; 
+	double *a, *b;
+	int y;
+	VipsBandFormat fmt;
+
+	if( VIPS_OBJECT_CLASS( vips_hist_norm_parent_class )->build( object ) )
+		return( -1 );
+
+	/* Need max for each channel.
+	 */
+	if( vips_stats( histogram->in, &t[0], NULL ) )
+		return( -1 ); 
+
+	/* Scale each channel by px / channel max
+	 */
+	px = VIPS_IMAGE_N_PELS( histogram->in );
+	bands = histogram->in->Bands;
+	if( !(a = VIPS_ARRAY( object, bands, double )) ||
+		!(b = VIPS_ARRAY( object, bands, double )) )
+		return( -1 );
+	for( y = 0; y < bands; y++ ) {
+		a[y] = px / *VIPS_MATRIX( t[0], 1, y + 1 );
+		b[y] = 0;
+	}
+
+	if( vips_linear( histogram->in, &t[1], a, b, bands, NULL ) )
+		return( -1 );
+
+	/* Make output format as small as we can.
+	 */
+	if( px <= 256 ) 
+		fmt = VIPS_FORMAT_UCHAR;
+	else if( px <= 65536 ) 
+		fmt = VIPS_FORMAT_USHORT;
+	else 
+		fmt = VIPS_FORMAT_UINT;
+
+	if( vips_cast( t[1], &t[2], fmt, NULL ) ||
+		vips_image_write( t[2], histogram->out ) )
+		return( -1 );
+
+	return( 0 );
+}
+
+static void
+vips_hist_norm_class_init( VipsHistNormClass *class )
+{
+	VipsObjectClass *object_class = (VipsObjectClass *) class;
+
+	object_class->nickname = "hist_norm";
+	object_class->description = _( "normalise histogram" );
+	object_class->build = vips_hist_norm_build;
+}
+
+static void
+vips_hist_norm_init( VipsHistNorm *hist_norm )
+{
+}
+
+/**
+ * vips_hist_norm:
+ * @in: input image
+ * @out: output image
+ *
+ * Normalise histogram ... normalise range to make it square (ie. max ==
+ * number of elements). Normalise each band separately.
+ *
+ * See also: vips_hist_cum().
+ *
+ * Returns: 0 on success, -1 on error
+ */
+int 
+vips_hist_norm( VipsImage *in, VipsImage **out, ... )
+{
+	va_list ap;
+	int result;
+
+	va_start( ap, out );
+	result = vips_call_split( "hist_norm", ap, in, out );
+	va_end( ap );
+
+	return( result );
+}
diff --git a/libvips/histogram/histogram.c b/libvips/histogram/histogram.c
index e137848a..c8408271 100644
--- a/libvips/histogram/histogram.c
+++ b/libvips/histogram/histogram.c
@@ -1,7 +1,8 @@
 /* base class for all histogram operations
  *
  * properties:
- * 	- single output image
+ * 	- one input image
+ * 	- one output image
  */
 
 /*
@@ -78,7 +79,6 @@ G_DEFINE_ABSTRACT_TYPE( VipsHistogram, vips_histogram, VIPS_TYPE_OPERATION );
 static int
 vips_histogram_build( VipsObject *object )
 {
-	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
 	VipsHistogram *histogram = VIPS_HISTOGRAM( object );
 
 #ifdef DEBUG
@@ -87,13 +87,10 @@ vips_histogram_build( VipsObject *object )
 	printf( "\n" );
 #endif /*DEBUG*/
 
-	g_object_set( histogram, "out", vips_image_new(), NULL ); 
-
 	if( VIPS_OBJECT_CLASS( vips_histogram_parent_class )->build( object ) )
 		return( -1 );
 
-	if( vips_check_hist( class->nickname, histogram->in ) )
-		return( -1 ); 
+	g_object_set( histogram, "out", vips_image_new(), NULL ); 
 
 	return( 0 );
 }
@@ -137,6 +134,12 @@ void
 vips_histogram_operation_init( void )
 {
 	extern GType vips_maplut_get_type( void ); 
+	extern GType vips_hist_cum_get_type( void ); 
+	extern GType vips_hist_norm_get_type( void ); 
+	extern GType vips_hist_equal_get_type( void ); 
 
 	vips_maplut_get_type(); 
+	vips_hist_cum_get_type(); 
+	vips_hist_norm_get_type(); 
+	vips_hist_equal_get_type(); 
 }
diff --git a/libvips/histogram/im_heq.c b/libvips/histogram/im_heq.c
deleted file mode 100644
index 6d985a17..00000000
--- a/libvips/histogram/im_heq.c
+++ /dev/null
@@ -1,79 +0,0 @@
-/* Histogram-equalise an image.
- *
- * Copyright: 1991, N. Dessipris.
- *
- * Author: Nicos Dessipris
- * Written on: 27/03/1991
- * Modified on : 
- * 16/6/93 J.Cupitt
- *	- im_ioflag() changed to im_iocheck()
- * 24/5/95 JC
- *	- ANSIfied and tidied up
- * 3/3/01 JC
- *	- more cleanup
- * 23/3/10
- * 	- gtkdoc
- */
-
-/*
-
-    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., 51 Franklin Street, Fifth Floor, Boston, MA
-    02110-1301  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 <vips/vips.h>
-
-/**
- * im_heq:
- * @in: input image
- * @out: output image
- * @bandno: band to equalise
- *
- * Histogram-equalise @in. Equalise using band @bandno, or if @bandno is -1,
- * equalise all bands.
- *
- * See also: im_lhisteq(), im_histgr(), im_histeq().
- *
- * Returns: 0 on success, -1 on error
- */
-int 
-im_heq( IMAGE *in, IMAGE *out, int bandno )
-{
-	IMAGE *t[2];
-
-	if( im_open_local_array( out, t, 2, "im_heq", "p" ) ||
-		im_histgr( in, t[0], bandno ) ||
-		im_histeq( t[0], t[1] ) ||
-		im_maplut( in, out, t[1] ) )
-		return( -1 );
-
-	return( 0 );
-}
diff --git a/libvips/histogram/im_histeq.c b/libvips/histogram/im_histeq.c
deleted file mode 100644
index 1ee1d36c..00000000
--- a/libvips/histogram/im_histeq.c
+++ /dev/null
@@ -1,229 +0,0 @@
-/* histogram normalisation and cumulativisation
- *
- * Author: N. Dessipris
- * Written on: 02/08/1990
- * 24/5/95 JC
- *	- tidied up and ANSIfied
- * 20/7/95 JC
- *	- smartened up again
- *	- now works for hists >256 elements
- * 3/3/01 JC
- *	- broken into cum and norm ... helps im_histspec()
- *	- better behaviour for >8 bit hists
- * 31/10/05 JC
- * 	- was broken for vertical histograms, gah
- * 	- neater im_histnorm()
- * 23/7/07
- * 	- eek, off by 1 for more than 1 band hists
- * 12/5/08
- * 	- histcum works for signed hists now as well
- * 24/3/10
- * 	- gtkdoc
- * 	- small cleanups
- */
-
-/*
-
-    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., 51 Franklin Street, Fifth Floor, Boston, MA
-    02110-1301  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 <vips/vips.h>
-
-#define ACCUMULATE( ITYPE, OTYPE ) { \
-	for( b = 0; b < nb; b++ ) { \
-		ITYPE *p = (ITYPE *) in->data; \
-		OTYPE *q = (OTYPE *) outbuf; \
-		OTYPE total; \
-		\
-		total = 0; \
-		for( x = b; x < mx; x += nb ) { \
-			total += p[x]; \
-			q[x] = total; \
-		} \
-	} \
-}
-
-/**
- * im_histcum:
- * @in: input image
- * @out: output image
- *
- * Form cumulative histogram. 
- *
- * See also: im_histnorm().
- *
- * Returns: 0 on success, -1 on error
- */
-int 
-im_histcum( IMAGE *in, IMAGE *out )
-{
-	const guint64 px = VIPS_IMAGE_N_PELS( in );
-	const int nb = vips_bandfmt_iscomplex( in->BandFmt ) ? 
-		in->Bands * 2 : in->Bands;
-	const guint64 mx = px * nb;
-
-	VipsPel *outbuf;		
-	guint64 b, x;
-
-	if( im_check_uncoded( "im_histcum", in ) ||
-		im_check_hist( "im_histcum", in ) ||
-		im_iocheck( in, out ) )
-		return( -1 );
-
-	if( im_cp_desc( out, in ) )
-		return( -1 );
-	out->Xsize = px;
-	out->Ysize = 1;
-	if( vips_bandfmt_isuint( in->BandFmt ) )
-		out->BandFmt = IM_BANDFMT_UINT;
-	else if( vips_bandfmt_isint( in->BandFmt ) )
-		out->BandFmt = IM_BANDFMT_INT;
-	if( im_setupout( out ) )
-		return( -1 );
-
-	if( !(outbuf = im_malloc( out, IM_IMAGE_SIZEOF_LINE( out ))) )
-                return( -1 );
-
-        switch( in->BandFmt ) {
-        case IM_BANDFMT_CHAR: 		
-		ACCUMULATE( signed char, signed int ); break; 
-        case IM_BANDFMT_UCHAR: 		
-		ACCUMULATE( unsigned char, unsigned int ); break; 
-        case IM_BANDFMT_SHORT: 		
-		ACCUMULATE( signed short, signed int ); break; 
-        case IM_BANDFMT_USHORT: 	
-		ACCUMULATE( unsigned short, unsigned int ); break; 
-        case IM_BANDFMT_INT: 		
-		ACCUMULATE( signed int, signed int ); break; 
-        case IM_BANDFMT_UINT: 		
-		ACCUMULATE( unsigned int, unsigned int ); break; 
-
-        case IM_BANDFMT_FLOAT: 		
-        case IM_BANDFMT_COMPLEX:	
-		ACCUMULATE( float, float ); break;
-        case IM_BANDFMT_DOUBLE:		
-        case IM_BANDFMT_DPCOMPLEX:	
-		ACCUMULATE( double, double ); break;
-
-        default:
-		g_assert( 0 );
-        }
-
-	if( im_writeline( 0, out, outbuf ) )
-		return( -1 );
-
-	return( 0 );
-}
-
-
-/**
- * im_histnorm:
- * @in: input image
- * @out: output image
- *
- * Normalise histogram ... normalise range to make it square (ie. max ==
- * number of elements). Normalise each band separately.
- *
- * See also: im_histcum().
- *
- * Returns: 0 on success, -1 on error
- */
-int 
-im_histnorm( IMAGE *in, IMAGE *out )
-{
-	const guint64 px = VIPS_IMAGE_N_PELS( in );
-	DOUBLEMASK *stats;
-	double *a, *b;
-	int y;
-	IMAGE *t1;
-	int fmt;
-
-	/* Need max for each channel.
-	 */
-	if( !(a = IM_ARRAY( out, in->Bands, double )) ||
-		!(b = IM_ARRAY( out, in->Bands, double )) ||
-		!(stats = im_stats( in )) )
-		return( -1 );
-
-	/* Scale each channel by px / channel max
-	 */
-	for( y = 0; y < in->Bands; y++ ) {
-		a[y] = px / VIPS_MASK( stats, 1, y + 1 );
-		b[y] = 0;
-	}
-
-	im_free_dmask( stats );
-
-	if( !(t1 = im_open_local( out, "im_histnorm:2", "p" )) ||
-		im_lintra_vec( in->Bands, a, in, b, t1 ) )
-		return( -1 );
-
-	/* Make output format as small as we can.
-	 */
-	if( px <= 256 ) 
-		fmt = IM_BANDFMT_UCHAR;
-	else if( px <= 65536 ) 
-		fmt = IM_BANDFMT_USHORT;
-	else 
-		fmt = IM_BANDFMT_UINT;
-
-	if( im_clip2fmt( t1, out, fmt ) )
-		return( -1 );
-
-	return( 0 );
-}
-
-/**
- * im_histeq:
- * @in: input image
- * @out: output image
- *
- * Histogram equalisation: normalised cumulative histogram. 
- *
- * See also: im_heq().
- *
- * Returns: 0 on success, -1 on error
- */
-int 
-im_histeq( IMAGE *in, IMAGE *out )
-{
-	IMAGE *t1;
-
-	/* Normalised cumulative.
-	 */
-	if( !(t1 = im_open_local( out, "im_histeq", "p" )) ||
-		im_histcum( in, t1 ) || 
-		im_histnorm( t1, out ) )
-		return( -1 );
-
-	return( 0 );
-}
diff --git a/libvips/histogram/maplut.c b/libvips/histogram/maplut.c
index f4ee5c31..56f0ced8 100644
--- a/libvips/histogram/maplut.c
+++ b/libvips/histogram/maplut.c
@@ -71,11 +71,11 @@
 
 #include <vips/vips.h>
 
-typedef struct _VipsMaplut {
-	VipsOperation parent_instance;
+#include "phistogram.h"
+
+typedef struct _VipsMaplut {
+	VipsHistogram parent_instance;
 
-	VipsImage *in;
-	VipsImage *out;
 	VipsImage *lut;
 
 	int fmt;		/* LUT image BandFmt */
@@ -88,9 +88,9 @@ typedef struct _VipsMaplut {
 
 } VipsMaplut;
 
-typedef VipsOperationClass VipsMaplutClass;
+typedef VipsHistogramClass VipsMaplutClass;
 
-G_DEFINE_TYPE( VipsMaplut, vips_maplut, VIPS_TYPE_OPERATION );
+G_DEFINE_TYPE( VipsMaplut, vips_maplut, VIPS_TYPE_HISTOGRAM );
 
 static void
 vips_maplut_preeval( VipsImage *image, VipsProgress *progress, 
@@ -142,13 +142,13 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 /* Map through n non-complex luts.
  */
 #define loop( OUT ) { \
-	int b = st->nb; \
+	int b = maplut->nb; \
 	\
 	for( y = to; y < bo; y++ ) { \
 		for( z = 0; z < b; z++ ) { \
 			VipsPel *p = VIPS_REGION_ADDR( ir, le, y ); \
 			OUT *q = (OUT *) VIPS_REGION_ADDR( or, le, y ); \
-			OUT *tlut = (OUT *) st->table[z]; \
+			OUT *tlut = (OUT *) maplut->table[z]; \
 			\
 			for( x = z; x < ne; x += b ) \
 				q[x] = tlut[p[x]]; \
@@ -165,7 +165,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 		for( z = 0; z < b; z++ ) { \
 			VipsPel *p = VIPS_REGION_ADDR( ir, le, y ) + z; \
 			OUT *q = (OUT *) VIPS_REGION_ADDR( or, le, y ) + z * 2; \
-			OUT *tlut = (OUT *) st->table[z]; \
+			OUT *tlut = (OUT *) maplut->table[z]; \
 			\
 			for( x = 0; x < ne; x += b ) { \
 				int n = p[x] * 2; \
@@ -179,19 +179,19 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 }
 
 #define loopg( IN, OUT ) { \
-	int b = st->nb; \
+	int b = maplut->nb; \
 	\
 	for( y = to; y < bo; y++ ) { \
 		for( z = 0; z < b; z++ ) { \
 			IN *p = (IN *) VIPS_REGION_ADDR( ir, le, y ); \
 			OUT *q = (OUT *) VIPS_REGION_ADDR( or, le, y ); \
-			OUT *tlut = (OUT *) st->table[z]; \
+			OUT *tlut = (OUT *) maplut->table[z]; \
 			\
 			for( x = z; x < ne; x += b ) { \
 				int index = p[x]; \
 				\
-				if( index > st->clp ) { \
-					index = st->clp; \
+				if( index > maplut->clp ) { \
+					index = maplut->clp; \
 					seq->overflow++; \
 				} \
 				\
@@ -208,13 +208,13 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 		for( z = 0; z < b; z++ ) { \
 			IN *p = (IN *) VIPS_REGION_ADDR( ir, le, y ) + z; \
 			OUT *q = (OUT *) VIPS_REGION_ADDR( or, le, y ) + z * 2; \
-			OUT *tlut = (OUT *) st->table[z]; \
+			OUT *tlut = (OUT *) maplut->table[z]; \
 			\
 			for( x = 0; x < ne; x += b ) { \
 				int index = p[x]; \
 				\
-				if( index > st->clp ) { \
-					index = st->clp; \
+				if( index > maplut->clp ) { \
+					index = maplut->clp; \
 					seq->overflow++; \
 				} \
 				\
@@ -230,7 +230,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 /* Map image through one non-complex lut.
  */
 #define loop1( OUT ) { \
-	OUT *tlut = (OUT *) st->table[0]; \
+	OUT *tlut = (OUT *) maplut->table[0]; \
 	\
 	for( y = to; y < bo; y++ ) { \
 		OUT *q = (OUT *) VIPS_REGION_ADDR( or, le, y ); \
@@ -244,7 +244,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 /* Map image through one complex lut.
  */
 #define loop1c( OUT ) { \
-	OUT *tlut = (OUT *) st->table[0]; \
+	OUT *tlut = (OUT *) maplut->table[0]; \
 	\
 	for( y = to; y < bo; y++ ) { \
 		OUT *q = (OUT *) VIPS_REGION_ADDR( or, le, y ); \
@@ -264,7 +264,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
  * index the lut carefully, and record the number of overflows we detect.
  */
 #define loop1g( IN, OUT ) { \
-	OUT *tlut = (OUT *) st->table[0]; \
+	OUT *tlut = (OUT *) maplut->table[0]; \
 	\
 	for( y = to; y < bo; y++ ) { \
 		OUT *q = (OUT *) VIPS_REGION_ADDR( or, le, y ); \
@@ -273,8 +273,8 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 		for( x = 0; x < ne; x++ ) { \
 			int index = p[x]; \
 			\
-			if( index > st->clp ) { \
-				index = st->clp; \
+			if( index > maplut->clp ) { \
+				index = maplut->clp; \
 				seq->overflow++; \
 			} \
 			\
@@ -284,7 +284,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 }
 
 #define loop1cg( IN, OUT ) { \
-	OUT *tlut = (OUT *) st->table[0]; \
+	OUT *tlut = (OUT *) maplut->table[0]; \
 	\
 	for( y = to; y < bo; y++ ) { \
 		OUT *q = (OUT *) VIPS_REGION_ADDR( or, le, y ); \
@@ -293,8 +293,8 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 		for( x = 0; x < ne; x++ ) { \
 			int index = p[x]; \
 			\
-			if( index > st->clp ) { \
-				index = st->clp; \
+			if( index > maplut->clp ) { \
+				index = maplut->clp; \
 				seq->overflow++; \
 			} \
 			\
@@ -308,7 +308,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 /* Map 1-band image through a many-band non-complex lut.
  */
 #define loop1m( OUT ) { \
-	OUT **tlut = (OUT **) st->table; \
+	OUT **tlut = (OUT **) maplut->table; \
 	\
 	for( y = to; y < bo; y++ ) { \
 		OUT *q = (OUT *) VIPS_REGION_ADDR( or, le, y ); \
@@ -317,7 +317,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 		for( i = 0, x = 0; x < np; x++ ) { \
 			int n = p[x]; \
 			\
-			for( z = 0; z < st->nb; z++, i++ ) \
+			for( z = 0; z < maplut->nb; z++, i++ ) \
 				q[i] = tlut[z][n]; \
 		} \
 	} \
@@ -326,7 +326,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 /* Map 1-band image through many-band complex lut.
  */
 #define loop1cm( OUT ) { \
-	OUT **tlut = (OUT **) st->table; \
+	OUT **tlut = (OUT **) maplut->table; \
 	\
 	for( y = to; y < bo; y++ ) { \
 		OUT *q = (OUT *) VIPS_REGION_ADDR( or, le, y ); \
@@ -335,7 +335,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 		for( x = 0; x < np; x++ ) { \
 			int n = p[x] * 2; \
 			\
-			for( z = 0; z < st->nb; z++ ) { \
+			for( z = 0; z < maplut->nb; z++ ) { \
 				q[0] = tlut[z][n]; \
 				q[1] = tlut[z][n+1]; \
 				q += 2; \
@@ -347,7 +347,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 /* Map 1-band uint or ushort image through a many-band non-complex LUT.
  */
 #define loop1gm( IN, OUT ) { \
-	OUT **tlut = (OUT **) st->table; \
+	OUT **tlut = (OUT **) maplut->table; \
 	\
 	for( y = to; y < bo; y++ ) { \
 		IN *p = (IN *) VIPS_REGION_ADDR( ir, le, y ); \
@@ -356,12 +356,12 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 		for( i = 0, x = 0; x < np; x++ ) { \
 			int n = p[x]; \
 			\
-			if( n > st->clp ) { \
-				n = st->clp; \
+			if( n > maplut->clp ) { \
+				n = maplut->clp; \
 				seq->overflow++; \
 			} \
 			\
-			for( z = 0; z < st->nb; z++, i++ ) \
+			for( z = 0; z < maplut->nb; z++, i++ ) \
 				q[i] = tlut[z][n]; \
 		} \
 	} \
@@ -370,7 +370,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 /* Map 1-band uint or ushort image through a many-band complex LUT.
  */
 #define loop1cgm( IN, OUT ) { \
-	OUT **tlut = (OUT **) st->table; \
+	OUT **tlut = (OUT **) maplut->table; \
 	\
 	for( y = to; y < bo; y++ ) { \
 		IN *p = (IN *) VIPS_REGION_ADDR( ir, le, y ); \
@@ -379,12 +379,12 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
 		for( x = 0; x < np; x++ ) { \
 			int n = p[x]; \
 			\
-			if( n > st->clp ) { \
-				n = st->clp; \
+			if( n > maplut->clp ) { \
+				n = maplut->clp; \
 				seq->overflow++; \
 			} \
 			\
-			for( z = 0; z < st->nb; z++ ) { \
+			for( z = 0; z < maplut->nb; z++ ) { \
 				q[0] = tlut[z][n * 2]; \
 				q[1] = tlut[z][n * 2 + 1]; \
 				q += 2; \
@@ -409,7 +409,7 @@ vips_maplut_start( VipsImage *out, void *a, void *b )
  * uchar.
  */
 #define outer_switch( UCHAR_F, UCHAR_FC, GEN_F, GEN_FC ) \
-	switch( st->fmt ) { \
+	switch( maplut->fmt ) { \
 	case VIPS_FORMAT_UCHAR:		inner_switch( UCHAR_F, GEN_F, \
 						unsigned char ); break; \
 	case VIPS_FORMAT_CHAR:		inner_switch( UCHAR_F, GEN_F, \
@@ -442,32 +442,28 @@ vips_maplut_gen( VipsRegion *or, void *vseq, void *a, void *b,
 {
 	VipsMaplutSequence *seq = (VipsMaplutSequence *) vseq;
 	VipsImage *in = (VipsImage *) a;
-	VipsMaplut *st = (VipsMaplut *) b;
+	VipsMaplut *maplut = (VipsMaplut *) b;
 	VipsRegion *ir = seq->ir;
 	VipsRect *r = &or->valid;
 	int le = r->left;
 	int to = r->top;
-	int bo = VIPS_RECT_BOTTOM(r);
+	int bo = VIPS_RECT_BOTTOM( r );
 	int np = r->width;			/* Pels across region */
 	int ne = VIPS_REGION_N_ELEMENTS( or );	/* Number of elements */
 
 	int x, y, z, i;
 
-	/* Get input ready.
-	 */
 	if( vips_region_prepare( ir, r ) )
 		return( -1 );
 
-	/* Process!
-	 */
-	if( st->nb == 1 )
+	if( maplut->nb == 1 )
 		/* One band lut.
 		 */
 		outer_switch( loop1, loop1c, loop1g, loop1cg ) 
 	else 
 		/* Many band lut.
 		 */
-		if( ir->im->Bands == 1 )
+		if( in->Bands == 1 )
 			/* ... but 1 band input.
 			 */
 			outer_switch( loop1m, loop1cm, loop1gm, loop1cgm ) 
@@ -511,6 +507,7 @@ static int
 vips_maplut_build( VipsObject *object )
 {
 	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
+	VipsHistogram *histogram = VIPS_HISTOGRAM( object );
 	VipsMaplut *maplut = (VipsMaplut *) object;
 	VipsImage **t = (VipsImage **) vips_object_local_array( object, 1 );
 
@@ -519,12 +516,10 @@ vips_maplut_build( VipsObject *object )
 	int i, x;
 	VipsPel *q;
 
-	g_object_set( maplut, "out", vips_image_new(), NULL ); 
-
 	if( VIPS_OBJECT_CLASS( vips_maplut_parent_class )->build( object ) )
 		return( -1 );
 
-	in = maplut->in;
+	in = histogram->in;
 	lut = maplut->lut;
 
 	if( vips_check_hist( class->nickname, lut ) ||
@@ -543,17 +538,17 @@ vips_maplut_build( VipsObject *object )
 		vips_image_pio_input( in ) )
 		return( -1 );
 
-	if( vips_image_copy_fieldsv( maplut->out, in, lut, NULL ) )
+	if( vips_image_copy_fieldsv( histogram->out, in, lut, NULL ) )
 		return( -1 );
-	vips_demand_hint( maplut->out, VIPS_DEMAND_STYLE_THINSTRIP, 
+	vips_demand_hint( histogram->out, VIPS_DEMAND_STYLE_THINSTRIP, 
 		in, lut, NULL );
-	maplut->out->BandFmt = lut->BandFmt;
+	histogram->out->BandFmt = lut->BandFmt;
 
 	/* Output has same number of bands as LUT, unless LUT has 1 band, in
 	 * which case output has same number of bands as input.
 	 */
 	if( lut->Bands != 1 )
-		maplut->out->Bands = lut->Bands;
+		histogram->out->Bands = lut->Bands;
 
 	g_signal_connect( in, "preeval", 
 		G_CALLBACK( vips_maplut_preeval ), maplut );
@@ -588,7 +583,7 @@ vips_maplut_build( VipsObject *object )
 			q += maplut->es;
 		}
 
-	if( vips_image_generate( maplut->out,
+	if( vips_image_generate( histogram->out,
 		vips_maplut_start, vips_maplut_gen, vips_maplut_stop, 
 		in, maplut ) )
 		return( -1 );
@@ -600,30 +595,18 @@ static void
 vips_maplut_class_init( VipsMaplutClass *class )
 {
 	GObjectClass *gobject_class = G_OBJECT_CLASS( class );
-	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS( class );
+	VipsObjectClass *object_class = VIPS_OBJECT_CLASS( class );
 	VipsOperationClass *operation_class = VIPS_OPERATION_CLASS( class );
 
 	gobject_class->set_property = vips_object_set_property;
 	gobject_class->get_property = vips_object_get_property;
 
-	vobject_class->nickname = "maplut";
-	vobject_class->description = _( "map an image though a lut" );
-	vobject_class->build = vips_maplut_build;
+	object_class->nickname = "maplut";
+	object_class->description = _( "map an image though a lut" );
+	object_class->build = vips_maplut_build;
 
 	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;
 
-	VIPS_ARG_IMAGE( class, "in", 0, 
-		_( "Input" ), 
-		_( "Input image" ),
-		VIPS_ARGUMENT_REQUIRED_INPUT, 
-		G_STRUCT_OFFSET( VipsMaplut, in ) );
-
-	VIPS_ARG_IMAGE( class, "out", 1, 
-		_( "Output" ), 
-		_( "Output image" ),
-		VIPS_ARGUMENT_REQUIRED_OUTPUT, 
-		G_STRUCT_OFFSET( VipsMaplut, out ) );
-
 	VIPS_ARG_IMAGE( class, "lut", 2, 
 		_( "LUT" ), 
 		_( "Look-up table image" ),
diff --git a/libvips/histogram/phistogram.h b/libvips/histogram/phistogram.h
index c82793d4..b623bd85 100644
--- a/libvips/histogram/phistogram.h
+++ b/libvips/histogram/phistogram.h
@@ -55,8 +55,6 @@ extern "C" {
 typedef struct _VipsHistogram {
 	VipsOperation parent_instance;
 
-	/* @in is checked to be a histogram.
-	 */
 	VipsImage *in;
 
 	VipsImage *out;
diff --git a/libvips/include/vips/histogram.h b/libvips/include/vips/histogram.h
index 07328638..1afe9601 100644
--- a/libvips/include/vips/histogram.h
+++ b/libvips/include/vips/histogram.h
@@ -40,6 +40,12 @@ extern "C" {
 
 int vips_maplut( VipsImage *in, VipsImage **out, VipsImage *lut, ... )
 	__attribute__((sentinel));
+int vips_hist_cum( VipsImage *in, VipsImage **out, ... )
+	__attribute__((sentinel));
+int vips_hist_norm( VipsImage *in, VipsImage **out, ... )
+	__attribute__((sentinel));
+int vips_hist_equal( VipsImage *in, VipsImage **out, ... )
+	__attribute__((sentinel));
 
 
 int im_histnD( VipsImage *in, VipsImage *out, int bins );
@@ -48,9 +54,6 @@ int im_hist_indexed( VipsImage *index, VipsImage *value, VipsImage *out );
 int im_invertlut( DOUBLEMASK *input, VipsImage *output, int lut_size );
 int im_project( VipsImage *in, VipsImage *hout, VipsImage *vout );
 
-int im_histnorm( VipsImage *in, VipsImage *out );
-int im_histcum( VipsImage *in, VipsImage *out );
-int im_histeq( VipsImage *in, VipsImage *out );
 int im_histspec( VipsImage *in, VipsImage *ref, VipsImage *out );
 int im_ismonotonic( VipsImage *lut, int *out );
 int im_histplot( VipsImage *in, VipsImage *out );
@@ -59,7 +62,6 @@ int im_hsp( VipsImage *in, VipsImage *ref, VipsImage *out );
 int im_mpercent( VipsImage *in, double percent, int *out );
 int im_mpercent_hist( VipsImage *hist, double percent, int *out );
 
-int im_heq( VipsImage *in, VipsImage *out, int bandno );
 int im_lhisteq( VipsImage *in, VipsImage *out, int xwin, int ywin );
 int im_stdif( VipsImage *in, VipsImage *out,
 	double a, double m0, double b, double s0, int xwin, int ywin );
diff --git a/libvips/include/vips/vips7compat.h b/libvips/include/vips/vips7compat.h
index c5057c68..1ef87008 100644
--- a/libvips/include/vips/vips7compat.h
+++ b/libvips/include/vips/vips7compat.h
@@ -852,6 +852,10 @@ int im_quadratic( IMAGE *in, IMAGE *out, IMAGE *coeff );
 int im_maplut( VipsImage *in, VipsImage *out, VipsImage *lut );
 int im_hist( VipsImage *in, VipsImage *out, int bandno );
 int im_histgr( VipsImage *in, VipsImage *out, int bandno );
+int im_histcum( VipsImage *in, VipsImage *out );
+int im_histnorm( VipsImage *in, VipsImage *out );
+int im_histeq( VipsImage *in, VipsImage *out );
+int im_heq( VipsImage *in, VipsImage *out, int bandno );
 
 /* ruby-vips uses this
  */
diff --git a/libvips/iofuncs/image.c b/libvips/iofuncs/image.c
index e4d4e62a..20caa021 100644
--- a/libvips/iofuncs/image.c
+++ b/libvips/iofuncs/image.c
@@ -1923,8 +1923,6 @@ vips_image_write_prepare( VipsImage *image )
 		break;
 
 	case VIPS_IMAGE_SETBUF:
-		/* Allocate memory.
-		 */
 		if( !image->data && 
 			!(image->data = vips_tracked_malloc( 
 				VIPS_IMAGE_SIZEOF_IMAGE( image ))) )