create funcs always make MULTIBAND

Before, they could make B_W for one-band output. This caused problems
with (for example) two black image bandjoined: the second band then
looked like an alpha to hasalpha() and enabled premultiply/unpremultiply
for operations like affine.

Now, it's always MULTIBAND. This is the generic multiband image type, so
you don't get any unexpected alpha handling.

ChangeLog

@@ -11,6 +11,7 @@
 - better header sniffing for small files
 - drop incompatible ICC profiles before save
 - better hasalpha rules
+- create funcs always make MULTIBAND (ie. no alpha)
 
 12/3/18 started 8.6.4
 - better fitting of fonts with overhanging edges, thanks Adrià 

libvips/create/black.c

@@ -15,6 +15,9 @@
  * 	- gtkdoc
  * 31/10/11
  * 	- redo as a class
+ * 3/4/18
+ * 	- always write MULTIBAND, otherwise when we join up these things it'll
+ * 	  look like we have an alpha
  */
 
 /*
@@ -97,8 +100,7 @@ vips_black_build( VipsObject *object )
 	vips_image_init_fields( create->out,
 		black->width, black->height, black->bands, 
 		VIPS_FORMAT_UCHAR, VIPS_CODING_NONE,
-                black->bands == 1 ? 
-			VIPS_INTERPRETATION_B_W : VIPS_INTERPRETATION_MULTIBAND,
+                VIPS_INTERPRETATION_MULTIBAND,
 		1.0, 1.0 );
 	vips_image_pipelinev( create->out, 
 		VIPS_DEMAND_STYLE_ANY, NULL );

libvips/create/gaussmat.c

@@ -134,7 +134,8 @@ vips_gaussmat_build( VipsObject *object )
 
 	vips_image_init_fields( create->out,
 		width, height, 1, 
-		VIPS_FORMAT_DOUBLE, VIPS_CODING_NONE, VIPS_INTERPRETATION_B_W,
+		VIPS_FORMAT_DOUBLE, VIPS_CODING_NONE, 
+		VIPS_INTERPRETATION_MULTIBAND,
 		1.0, 1.0 ); 
 	vips_image_pipelinev( create->out, 
 		VIPS_DEMAND_STYLE_ANY, NULL );

libvips/create/gaussnoise.c

@@ -134,7 +134,7 @@ vips_gaussnoise_build( VipsObject *object )
 	vips_image_init_fields( create->out,
 		gaussnoise->width, gaussnoise->height, 1,
 		VIPS_FORMAT_FLOAT, VIPS_CODING_NONE,
-		VIPS_INTERPRETATION_B_W, 1.0, 1.0 );
+		VIPS_INTERPRETATION_MULTIBAND, 1.0, 1.0 );
 	vips_image_pipelinev( create->out, 
 		VIPS_DEMAND_STYLE_ANY, NULL );
 

libvips/create/logmat.c

@@ -153,7 +153,8 @@ vips_logmat_build( VipsObject *object )
 
 	vips_image_init_fields( create->out,
 		width, height, 1, 
-		VIPS_FORMAT_DOUBLE, VIPS_CODING_NONE, VIPS_INTERPRETATION_B_W,
+		VIPS_FORMAT_DOUBLE, VIPS_CODING_NONE, 
+		VIPS_INTERPRETATION_MULTIBAND,
 		1.0, 1.0 ); 
 	vips_image_pipelinev( create->out, 
 		VIPS_DEMAND_STYLE_ANY, NULL );

libvips/create/perlin.c

@@ -249,7 +249,7 @@ vips_perlin_build( VipsObject *object )
 	vips_image_init_fields( create->out,
 		perlin->width, perlin->height, 1,
 		perlin->uchar ? VIPS_FORMAT_UCHAR : VIPS_FORMAT_FLOAT, 
-		VIPS_CODING_NONE, VIPS_INTERPRETATION_B_W,
+		VIPS_CODING_NONE, VIPS_INTERPRETATION_MULTIBAND,
 		1.0, 1.0 );
 	vips_image_pipelinev( create->out,
 		VIPS_DEMAND_STYLE_ANY, NULL );

libvips/create/point.c

@@ -109,10 +109,9 @@ vips_point_build( VipsObject *object )
 			return( -1 );
 		in = t[2];
 
-		/* uchar mode always does B_W. We don't want FOURIER or
-		 * whatever in this case.
+		/* We don't want FOURIER or whatever in this case.
 		 */
-		in->Type = VIPS_INTERPRETATION_B_W;
+		in->Type = VIPS_INTERPRETATION_MULTIBAND;
 	}
 
 	if( vips_image_write( in, create->out ) )
@@ -137,7 +136,7 @@ vips_point_class_init( VipsPointClass *class )
 	class->point = NULL; 
 	class->min = -1.0; 
 	class->max = 1.0; 
-	class->interpretation = VIPS_INTERPRETATION_B_W;
+	class->interpretation = VIPS_INTERPRETATION_MULTIBAND;
 
 	VIPS_ARG_INT( class, "width", 2, 
 		_( "Width" ), 

libvips/create/text.c

@@ -379,7 +379,8 @@ vips_text_build( VipsObject *object )
 
 	vips_image_init_fields( create->out,
 		text->bitmap.width, text->bitmap.rows, 1, 
-		VIPS_FORMAT_UCHAR, VIPS_CODING_NONE, VIPS_INTERPRETATION_B_W,
+		VIPS_FORMAT_UCHAR, VIPS_CODING_NONE, 
+		VIPS_INTERPRETATION_MULTIBAND,
 		1.0, 1.0 ); 
 	vips_image_pipelinev( create->out, 
 		VIPS_DEMAND_STYLE_ANY, NULL );

libvips/create/worley.c

@@ -281,7 +281,8 @@ vips_worley_build( VipsObject *object )
 
 	vips_image_init_fields( create->out,
 		worley->width, worley->height, 1,
-		VIPS_FORMAT_FLOAT, VIPS_CODING_NONE, VIPS_INTERPRETATION_B_W,
+		VIPS_FORMAT_FLOAT, VIPS_CODING_NONE, 
+		VIPS_INTERPRETATION_MULTIBAND,
 		1.0, 1.0 );
 	vips_image_pipelinev( create->out,
 		VIPS_DEMAND_STYLE_ANY, NULL );