diff --git a/ChangeLog b/ChangeLog
index 3476ca74..fce78806 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -44,6 +44,8 @@
 - dilate/erode do (!=0) on non-uchar images
 - add multipass Orc to im_conv(), 3.5x faster for 5x5 mask
 - im_profile() works for any image format, any number of bands
+- im_rank_image() works for mix of formats, bands
+- morph gtk-doc done
 
 12/5/10 started 7.22.2
 - the conditional image of ifthenelse can be any format, a (!=0) is added if
diff --git a/doc/reference/Makefile.am b/doc/reference/Makefile.am
index 0b2b88eb..64872d31 100644
--- a/doc/reference/Makefile.am
+++ b/doc/reference/Makefile.am
@@ -59,7 +59,7 @@ EXTRA_HFILES=
 
 # Header files to ignore when scanning. Use base file name, no paths
 # e.g. IGNORE_HFILES=gtkdebug.h gtkintl.h
-IGNORE_HFILES=merge.h debug.h internal.h intl.h CImg.h im_video_v4l1.h global_balance.h dbh.h base64.h templates.h mosaic.h deprecated.h thread.h private.h internal.h almostdeprecated.h inlines.h struct.h disp.h
+IGNORE_HFILES=merge.h debug.h internal.h intl.h CImg.h im_video_v4l1.h global_balance.h dbh.h base64.h templates.h mosaic.h deprecated.h thread.h private.h internal.h almostdeprecated.h inlines.h struct.h disp.h vector.h
 
 # Images to copy into HTML directory.
 # e.g. HTML_IMAGES=$(top_srcdir)/gtk/stock-icons/stock_about_24.png
diff --git a/doc/reference/libvips-docs.sgml.in b/doc/reference/libvips-docs.sgml.in
index d0c2048c..6dc0e3cf 100644
--- a/doc/reference/libvips-docs.sgml.in
+++ b/doc/reference/libvips-docs.sgml.in
@@ -43,11 +43,11 @@
     <xi:include href="xml/histograms_lut.xml"/>
     <xi:include href="xml/inplace.xml"/>
     <xi:include href="xml/mask.xml"/>
+    <xi:include href="xml/morphology.xml"/>
   </chapter>
 
   <chapter>
     <title>VIPS operation API by section (no gtkdoc comments yet)</title>
-    <xi:include href="xml/morphology.xml"/>
     <xi:include href="xml/resample.xml"/>
     <xi:include href="xml/mosaicing.xml"/>
     <xi:include href="xml/other.xml"/>
diff --git a/libvips/arithmetic/im_add.c b/libvips/arithmetic/im_add.c
index cba87e7a..676a5fa8 100644
--- a/libvips/arithmetic/im_add.c
+++ b/libvips/arithmetic/im_add.c
@@ -237,7 +237,7 @@ im__formatalike( IMAGE *in1, IMAGE *in2, IMAGE *out1, IMAGE *out2 )
 /* Make an n-band image. Input 1 or n bands.
  */
 int
-im__bandup( IMAGE *in, IMAGE *out, int n )
+im__bandup( const char *domain, IMAGE *in, IMAGE *out, int n )
 {
 	IMAGE *bands[256];
 	int i;
@@ -245,11 +245,11 @@ im__bandup( IMAGE *in, IMAGE *out, int n )
 	if( in->Bands == n ) 
 		return( im_copy( in, out ) );
 	if( in->Bands != 1 ) {
-		im_error( "im__bandup", _( "not one band or %d bands" ), n );
+		im_error( domain, _( "not one band or %d bands" ), n );
 		return( -1 );
 	}
 	if( n > 256 || n < 1 ) {
-		im_error( "im__bandup", "%s", _( "bad bands" ) );
+		im_error( domain, "%s", _( "bad bands" ) );
 		return( -1 );
 	}
 
@@ -260,12 +260,35 @@ im__bandup( IMAGE *in, IMAGE *out, int n )
 }
 
 int
-im__bandalike( IMAGE *in1, IMAGE *in2, IMAGE *out1, IMAGE *out2 )
+im__bandalike_vec( const char *domain, IMAGE **in, IMAGE **out, int n )
 {
-	if( im_check_bands_1orn( "im__bandalike", in1, in2 ) )
-		return( -1 );
-	if( im__bandup( in1, out1, IM_MAX( in1->Bands, in2->Bands ) ) ||
-		im__bandup( in2, out2, IM_MAX( in1->Bands, in2->Bands ) ) )
+	int i;
+	int max_bands;
+
+	g_assert( n >= 1 );
+
+	max_bands = in[0]->Bands;
+	for( i = 1; i < n; i++ )
+		max_bands = IM_MAX( max_bands, in[i]->Bands );
+	for( i = 0; i < n; i++ )
+		if( im__bandup( domain, in[i], out[i], max_bands ) )
+			return( -1 );
+
+	return( 0 );
+}
+
+int
+im__bandalike( const char *domain, 
+	IMAGE *in1, IMAGE *in2, IMAGE *out1, IMAGE *out2 )
+{
+	IMAGE *in[2];
+	IMAGE *out[2];
+
+	in[0] = in1;
+	in[1] = in2;
+	out[0] = out1;
+	out[1] = out2;
+	if( im__bandalike_vec( domain, in, out, 2 ) )
 		return( -1 );
 
 	return( 0 );
@@ -301,7 +324,7 @@ im__arith_binary( const char *domain,
 	 */
 	if( im_open_local_array( out, t, 4, domain, "p" ) ||
 		im__formatalike( in1, in2, t[0], t[1] ) ||
-		im__bandalike( t[0], t[1], t[2], t[3] ) )
+		im__bandalike( domain, t[0], t[1], t[2], t[3] ) )
 		return( -1 );
 
 	/* Generate the output.
diff --git a/libvips/arithmetic/im_remainder.c b/libvips/arithmetic/im_remainder.c
index 5dfd716c..144eb988 100644
--- a/libvips/arithmetic/im_remainder.c
+++ b/libvips/arithmetic/im_remainder.c
@@ -262,7 +262,7 @@ make_pixel( IMAGE *out, VipsBandFmt fmt, int n, double *p )
 }
 
 int 
-im__arith_binary_const( const char *name,
+im__arith_binary_const( const char *domain,
 	IMAGE *in, IMAGE *out, 
 	int n, double *c, VipsBandFmt vfmt,
 	int format_table[10], 
@@ -271,8 +271,8 @@ im__arith_binary_const( const char *name,
 	PEL *vector;
 
 	if( im_piocheck( in, out ) ||
-		im_check_vector( name, n, in ) ||
-		im_check_uncoded( name, in ) )
+		im_check_vector( domain, n, in ) ||
+		im_check_uncoded( domain, in ) )
 		return( -1 );
 	if( im_cp_desc( out, in ) )
 		return( -1 );
@@ -297,8 +297,8 @@ im__arith_binary_const( const char *name,
 	if( n > 1 && out->Bands == 1 ) {
 		IMAGE *t;
 
-		if( !(t = im_open_local( out, "arith_binary_const", "p" )) ||
-			im__bandup( in, t, n ) )
+		if( !(t = im_open_local( out, domain, "p" )) ||
+			im__bandup( domain, in, t, n ) )
 			return( -1 );
 
 		in = t;
diff --git a/libvips/conversion/im_gbandjoin.c b/libvips/conversion/im_gbandjoin.c
index b9af40d8..1fca2e8f 100644
--- a/libvips/conversion/im_gbandjoin.c
+++ b/libvips/conversion/im_gbandjoin.c
@@ -66,7 +66,7 @@
 /* Struct we carry stuff around in.
  */
 typedef struct joins {
-	int n;		/* Number of input images */
+	int n;			/* Number of input images */
 	IMAGE **in;		/* Array of input images, NULL-terminated */
 	int *is;		/* An int for SIZEOF_PEL() for each image */
 } Join;
diff --git a/libvips/conversion/im_insert.c b/libvips/conversion/im_insert.c
index 68d91365..1651ab7c 100644
--- a/libvips/conversion/im_insert.c
+++ b/libvips/conversion/im_insert.c
@@ -97,7 +97,7 @@ im__insert_base( const char *domain,
 	 */
 	if( im_open_local_array( out, t, 4, domain, "p" ) ||
 		im__formatalike( in1, in2, t[0], t[1] ) ||
-		im__bandalike( t[0], t[1], t[2], t[3] ) ||
+		im__bandalike( domain, t[0], t[1], t[2], t[3] ) ||
 		!(vec = im_allocate_input_array( out, t[2], t[3], NULL )) )
 		return( NULL );
 
diff --git a/libvips/conversion/im_ri2c.c b/libvips/conversion/im_ri2c.c
index 9d0c8c4a..e1913235 100644
--- a/libvips/conversion/im_ri2c.c
+++ b/libvips/conversion/im_ri2c.c
@@ -97,7 +97,7 @@ join_buffer( PEL **p, PEL *q, int n, IMAGE *im )
  *
  * Compose two real images to make a complex image. If either @in1 or @in2 are
  * %IM_BANDFMT_DOUBLE, @out is %IM_BANDFMT_DPCOMPLEX. Otherwise @out is
- * %IM_BANDFMT_COMPLEX. @in1 becomes the real component fo @out and @in2 the
+ * %IM_BANDFMT_COMPLEX. @in1 becomes the real component of @out and @in2 the
  * imaginary.
  *
  * If the number of bands differs, one of the images 
@@ -105,10 +105,6 @@ join_buffer( PEL **p, PEL *q, int n, IMAGE *im )
  * one-band image by joining n copies of the one-band image together, and then
  * the two n-band images are operated upon.
  *
- * The two input images are cast up to the smallest common type (see table 
- * Smallest common format in 
- * <link linkend="VIPS-arithmetic">arithmetic</link>).
- *
  * See also: im_c2real(), im_c2imag().
  *
  * Returns: 0 on success, -1 on error
@@ -141,7 +137,7 @@ im_ri2c( IMAGE *in1, IMAGE *in2, IMAGE *out )
 	if( im_open_local_array( out, t, 4, "im_ri2c", "p" ) ||
 		im_clip2fmt( in1, t[0], fmt ) ||
 		im_clip2fmt( in2, t[1], fmt ) ||
-		im__bandalike( t[0], t[1], t[2], t[3] ) )
+		im__bandalike( "im_ri2c", t[0], t[1], t[2], t[3] ) )
 		return( -1 );
 
 	/* Remember to NULL-terminate.
diff --git a/libvips/include/vips/internal.h b/libvips/include/vips/internal.h
index 63084901..43cf6047 100644
--- a/libvips/include/vips/internal.h
+++ b/libvips/include/vips/internal.h
@@ -151,15 +151,17 @@ char *im__gslist_gvalue_get( const GSList *list );
 
 void im__buffer_init( void );
 
-int im__bandup( IMAGE *in, IMAGE *out, int n );
-int im__bandalike( IMAGE *in1, IMAGE *in2, IMAGE *out1, IMAGE *out2 );
+int im__bandup( const char *domain, IMAGE *in, IMAGE *out, int n );
+int im__bandalike_vec( const char *domain, IMAGE **in, IMAGE **out, int n );
+int im__bandalike( const char *domain, 
+	IMAGE *in1, IMAGE *in2, IMAGE *out1, IMAGE *out2 );
 int im__formatalike_vec( IMAGE **in, IMAGE **out, int n );
 int im__formatalike( IMAGE *in1, IMAGE *in2, IMAGE *out1, IMAGE *out2 );
-int im__arith_binary( const char *name, 
+int im__arith_binary( const char *domain, 
 	IMAGE *in1, IMAGE *in2, IMAGE *out, 
 	int format_table[10], 
 	im_wrapmany_fn fn, void *b );
-int im__arith_binary_const( const char *name,
+int im__arith_binary_const( const char *domain,
 	IMAGE *in, IMAGE *out, 
 	int n, double *c, VipsBandFmt vfmt,
 	int format_table[10], 
diff --git a/libvips/include/vips/morphology.h b/libvips/include/vips/morphology.h
index 658babc8..1ec61c16 100644
--- a/libvips/include/vips/morphology.h
+++ b/libvips/include/vips/morphology.h
@@ -37,15 +37,15 @@
 extern "C" {
 #endif /*__cplusplus*/
 
-int im_dilate( IMAGE *in, IMAGE *out, INTMASK *m );
-int im_erode( IMAGE *in, IMAGE *out, INTMASK *m );
+int im_dilate( IMAGE *in, IMAGE *out, INTMASK *mask );
+int im_erode( IMAGE *in, IMAGE *out, INTMASK *mask );
 
-int im_rank( IMAGE *in, IMAGE *out, int xsize, int ysize, int order );
+int im_rank( IMAGE *in, IMAGE *out, int width, int height, int index );
 int im_rank_image( IMAGE **in, IMAGE *out, int n, int index );
 int im_maxvalue( IMAGE **in, IMAGE *out, int n );
 
 int im_cntlines( IMAGE *im, double *nolines, int flag );
-int im_zerox( IMAGE *in, IMAGE *out, int flag );
+int im_zerox( IMAGE *in, IMAGE *out, int sign );
 int im_profile( IMAGE *in, IMAGE *out, int dir );
 int im_label_regions( IMAGE *test, IMAGE *mask, int *segments );
 
diff --git a/libvips/inplace/im_draw_image.c b/libvips/inplace/im_draw_image.c
index acc27035..9f09c9cc 100644
--- a/libvips/inplace/im_draw_image.c
+++ b/libvips/inplace/im_draw_image.c
@@ -89,7 +89,7 @@ im__inplace_base( const char *domain,
 	/* Cast sub to match main in bands and format.
 	 */
 	if( im_open_local_array( out, t, 2, domain, "p" ) ||
-		im__bandup( sub, t[0], main->Bands ) ||
+		im__bandup( domain, sub, t[0], main->Bands ) ||
 		im_clip2fmt( t[0], t[1], main->BandFmt ) )
 		return( NULL );
 
diff --git a/libvips/iofuncs/check.c b/libvips/iofuncs/check.c
index b3f36468..8257a659 100644
--- a/libvips/iofuncs/check.c
+++ b/libvips/iofuncs/check.c
@@ -711,7 +711,7 @@ int
 im_check_bands( const char *domain, IMAGE *im, int bands )
 {
 	if( im->Bands != bands ) {
-		im_error( domain, _( "image must %d bands" ), bands );
+		im_error( domain, _( "image must have %d bands" ), bands );
 		return( -1 );
 	}
 
@@ -735,7 +735,8 @@ int
 im_check_bands_1or3( const char *domain, IMAGE *im )
 {
 	if( im->Bands != 1 && im->Bands != 3 ) {
-		im_error( domain, "%s", _( "image must one or three bands" ) );
+		im_error( domain, "%s", 
+			_( "image must have one or three bands" ) );
 		return( -1 );
 	}
 
diff --git a/libvips/morphology/im_rank.c b/libvips/morphology/im_rank.c
index 8be9e032..536a4573 100644
--- a/libvips/morphology/im_rank.c
+++ b/libvips/morphology/im_rank.c
@@ -70,7 +70,7 @@
 typedef struct {
 	IMAGE *in, *out;	/* Images we run */
 	int xsize, ysize;	/* Window size */
-	int order;		/* Element select */
+	int index;		/* Element select */
 	int n;			/* xsize * ysize */
 } RankInfo;
 
@@ -142,7 +142,7 @@ rank_start( IMAGE *out, void *a, void *b )
 			d += ls; \
 		} \
 		\
-		/* Rearrange sort[] to make the order-th element the order-th 
+		/* Rearrange sort[] to make the index-th element the index-th 
 		 * smallest, adapted from Numerical Recipes in C.
 		 */ \
 		lower = 0;	/* Range we know the result lies in */ \
@@ -202,14 +202,14 @@ rank_start( IMAGE *out, void *a, void *b )
 				\
 				/* Move to partition with the kth element. 
 				 */ \
-				if( j >= rnk->order ) \
+				if( j >= rnk->index ) \
 					upper = j - 1; \
-				if( j <= rnk->order ) \
+				if( j <= rnk->index ) \
 					lower = i; \
 			} \
 		} \
 		\
-		q[x] = sort[rnk->order]; \
+		q[x] = sort[rnk->index]; \
 	} \
 }
 
@@ -320,9 +320,9 @@ rank_gen( REGION *or, void *vseq, void *a, void *b )
 	ls = IM_REGION_LSKIP( ir ) / IM_IMAGE_SIZEOF_ELEMENT( in );
 
 	for( y = to; y < bo; y++ ) { 
-		if( rnk->order == 0 )
+		if( rnk->index == 0 )
 			SWITCH( LOOP_MIN )
-		else if( rnk->order == rnk->n - 1 ) 
+		else if( rnk->index == rnk->n - 1 ) 
 			SWITCH( LOOP_MAX )
 		else 
 			SWITCH( LOOP_SELECT ) }
@@ -333,7 +333,7 @@ rank_gen( REGION *or, void *vseq, void *a, void *b )
 /* Rank filter.
  */
 int
-im_rank_raw( IMAGE *in, IMAGE *out, int xsize, int ysize, int order )
+im_rank_raw( IMAGE *in, IMAGE *out, int xsize, int ysize, int index )
 {
 	RankInfo *rnk;
 
@@ -342,7 +342,7 @@ im_rank_raw( IMAGE *in, IMAGE *out, int xsize, int ysize, int order )
 		im_check_noncomplex( "im_rank", in ) )
 		return( -1 );
 	if( xsize > 1000 || ysize > 1000 || xsize <= 0 || ysize <= 0 || 
-		order < 0 || order > xsize * ysize - 1 ) {
+		index < 0 || index > xsize * ysize - 1 ) {
 		im_error( "im_rank", "%s", _( "bad parameters" ) );
 		return( -1 );
 	}
@@ -355,7 +355,7 @@ im_rank_raw( IMAGE *in, IMAGE *out, int xsize, int ysize, int order )
 	rnk->out = out;
 	rnk->xsize = xsize;
 	rnk->ysize = ysize;
-	rnk->order = order;
+	rnk->index = index;
 	rnk->n = xsize * ysize;
 
 	/* Prepare output. Consider a 7x7 window and a 7x7 image --- the output
@@ -394,12 +394,12 @@ im_rank_raw( IMAGE *in, IMAGE *out, int xsize, int ysize, int order )
  * @out: output image
  * @width: window width
  * @height: window height
- * @order: select pixel
+ * @index: select pixel
  *
  * im_rank() does rank filtering on an image. A window of size @width by
  * @height is passed over the image. At each position, the pixels inside the 
- * window are sorted into ascending order and the pixel at position @order is 
- * output. @order numbers from 0.
+ * window are sorted into ascending order and the pixel at position @index is 
+ * output. @index numbers from 0.
  *
  * It works for any non-complex image type, with any number of bands. 
  * The input is expanded by copying edge pixels before performing the 
@@ -418,7 +418,7 @@ im_rank_raw( IMAGE *in, IMAGE *out, int xsize, int ysize, int order )
  * Returns: 0 on success, -1 on error
  */
 int 
-im_rank( IMAGE *in, IMAGE *out, int width, int height, int order )
+im_rank( IMAGE *in, IMAGE *out, int width, int height, int index )
 {
 	IMAGE *t1;
 
@@ -426,7 +426,7 @@ im_rank( IMAGE *in, IMAGE *out, int width, int height, int order )
 		im_embed( in, t1, 1, 
 			width / 2, height / 2, 
 			in->Xsize + width - 1, in->Ysize + height - 1 ) ||
-		im_rank_raw( t1, out, width, height, order ) )
+		im_rank_raw( t1, out, width, height, index ) )
 		return( -1 );
 
 	out->Xoffset = 0;
diff --git a/libvips/morphology/im_rank_image.c b/libvips/morphology/im_rank_image.c
index e486e24d..c9e32de1 100644
--- a/libvips/morphology/im_rank_image.c
+++ b/libvips/morphology/im_rank_image.c
@@ -5,6 +5,7 @@
  * 10/11/10
  * 	- gtkdoc
  * 	- cleanups
+ * 	- any mix of formats and bands
  */
 
 /*
@@ -43,6 +44,7 @@
 #include <assert.h>
 
 #include <vips/vips.h>
+#include <vips/internal.h>
 
 #ifdef WITH_DMALLOC
 #include <dmalloc.h>
@@ -63,7 +65,7 @@ static Rank *
 rank_new( IMAGE **in, IMAGE *out, int n, int index )
 {
 	Rank *rank;
-	int i;
+	IMAGE **t;
 
 	if( !(rank = IM_NEW( out, Rank )) )
 		return( NULL );
@@ -71,10 +73,17 @@ rank_new( IMAGE **in, IMAGE *out, int n, int index )
 	rank->n = n;
 	rank->index = index;
 	rank->out = out;
-	if( !(rank->in = IM_ARRAY( out, n + 1, IMAGE * )) ) 
+	if( !(t = IM_ARRAY( out, n, IMAGE * )) || 
+		!(rank->in = IM_ARRAY( out, n + 1, IMAGE * )) ) 
+		return( NULL );
+
+	/* Cast inputs up to a common format, common bands.
+	 */
+	if( im_open_local_array( out, rank->in, n, "im_rank_image", "p" ) ||
+		im_open_local_array( out, rank->in, n, "im_rank_image", "p" ) ||
+		im__bandalike_vec( "im_rank_image", in, t, n ) ||
+		im__formatalike_vec( t, rank->in, n ) )
 		return( NULL );
-	for( i = 0; i < n; i++ ) 
-		rank->in[i] = in[i];
 	rank->in[n] = NULL;
 
 	return( rank );
@@ -270,23 +279,27 @@ rank_gen( REGION *or, void *vseq, void *a, void *b )
  * @in: input image array
  * @out: output image
  * @n: number of input images
- * @order: select pixel
+ * @index: select pixel
  *
- * im_rank_image() sorts the input images pixel-wise, then outputs an image 
- * in which each pixel is selected from the sorted list by the 
- * @order parameter. For example, if @order
+ * im_rank_image() sorts the images @in pixel-wise, then outputs an 
+ * image in which each pixel is selected from the sorted list by the 
+ * @index parameter. For example, if @index
  * is zero, then each output pixel will be the minimum of all the 
  * corresponding input pixels. 
  *
- * It works for any uncoded, non-complex image type. All input images must 
- * match in size, format, and number of bands.
+ * It works for any uncoded, non-complex image type. Images are cast up to the
+ * smallest common-format.
+ *
+ * Any image can have either 1 band or n bands, where n is the same for all
+ * the non-1-band images. Single band images are then effectively copied to 
+ * make n-band images.
  *
  * See also: im_rank(), im_maxvalue().
  *
  * Returns: 0 on success, -1 on error
  */
 int
-im_rank_image( IMAGE **in, IMAGE *out, int n, int order )
+im_rank_image( IMAGE **in, IMAGE *out, int n, int index )
 {
 	int i;
 	Rank *rank;
@@ -295,7 +308,7 @@ im_rank_image( IMAGE **in, IMAGE *out, int n, int order )
 		im_error( "im_rank_image", "%s", _( "zero input images!" ) );
 		return( -1 );
 	}
-	if( order < 0 || order > n - 1 ) {
+	if( index < 0 || index > n - 1 ) {
 		im_error( "im_rank_image", 
 			_( "index should be in range 0 - %d" ), n - 1 );
 		return( -1 );
@@ -306,12 +319,10 @@ im_rank_image( IMAGE **in, IMAGE *out, int n, int order )
 		if( im_pincheck( in[i] ) ||
 			im_check_uncoded( "im_rank_image", in[i] ) ||
 			im_check_noncomplex( "im_rank_image", in[i] ) ||
-			im_check_size_same( "im_rank_image", in[i], in[0] ) ||
-			im_check_format_same( "im_rank_image", in[i], in[0] ) ||
-			im_check_bands_same( "im_rank_image", in[i], in[0] ) )
+			im_check_size_same( "im_rank_image", in[i], in[0] ) )
 			return( -1 );
 
-	if( !(rank = rank_new( in, out, n, order )) ||
+	if( !(rank = rank_new( in, out, n, index )) ||
 		im_cp_desc_array( out, rank->in ) ||
 		im_demand_hint_array( out, IM_THINSTRIP, rank->in )  ||
 		im_generate( out, 
@@ -327,16 +338,17 @@ im_rank_image( IMAGE **in, IMAGE *out, int n, int order )
  * @out: output image
  * @n: number of input images
  *
- * im_maxvalue() sorts the input images pixel-wise, then outputs an image 
- * in which each pixel is 
- * @order parameter. For example, if @order
- * is zero, then each output pixel will be the minimum of all the 
- * corresponding input pixels. 
+ * im_maxvalue() is a convenience function over im_rank_image(). It sorts the 
+ * input images pixel-wise, then outputs an image 
+ * in which each pixel is the maximum  of all the corresponding input images. 
+ * It works for any uncoded, non-complex image type. Images are cast up to the
+ * smallest common-format.
  *
- * It works for any uncoded, non-complex image type. All input images must 
- * match in size, format, and number of bands.
+ * Any image can have either 1 band or n bands, where n is the same for all
+ * the non-1-band images. Single band images are then effectively copied to 
+ * make n-band images.
  *
- * See also: im_rank(), im_maxvalue().
+ * See also: im_rank_image().
  *
  * Returns: 0 on success, -1 on error
  */
diff --git a/libvips/morphology/im_zerox.c b/libvips/morphology/im_zerox.c
index 7365c6e3..09b4bd44 100644
--- a/libvips/morphology/im_zerox.c
+++ b/libvips/morphology/im_zerox.c
@@ -137,7 +137,7 @@ zerox_gen( REGION *or, void *seq, void *a, void *b )
  * Returns: 0 on success, -1 on error
  */
 int 
-im_zerox( IMAGE *in, IMAGE *out, int flag )
+im_zerox( IMAGE *in, IMAGE *out, int sign )
 {
 	IMAGE *t1;
 
diff --git a/libvips/relational/im_blend.c b/libvips/relational/im_blend.c
index f38ccfeb..afb2d2f5 100644
--- a/libvips/relational/im_blend.c
+++ b/libvips/relational/im_blend.c
@@ -378,7 +378,7 @@ im_blend( IMAGE *c, IMAGE *a, IMAGE *b, IMAGE *out )
 	/* Make a and b match in bands and format.
 	 */
 	if( im__formatalike( a, b, t[2], t[3] ) ||
-		im__bandalike( t[2], t[3], t[4], t[5] ) )
+		im__bandalike( "im_blend", t[2], t[3], t[4], t[5] ) )
 		return( -1 );
 
 	if( blend( c, t[4], t[5], t[6] ) )
diff --git a/libvips/relational/im_ifthenelse.c b/libvips/relational/im_ifthenelse.c
index 618ac8d0..d03e72ca 100644
--- a/libvips/relational/im_ifthenelse.c
+++ b/libvips/relational/im_ifthenelse.c
@@ -216,7 +216,7 @@ im_ifthenelse( IMAGE *c, IMAGE *a, IMAGE *b, IMAGE *out )
 	 * special-case this in code above ^^^ for speed.
 	 */
 	if( im__formatalike( a, b, t[0], t[1] ) ||
-		im__bandalike( t[0], t[1], t[2], t[3] ) )
+		im__bandalike( "im_ifthenelse", t[0], t[1], t[2], t[3] ) )
 		return( -1 );
 
 	/* If c is not uchar, do (!=0) to make a uchar image.