im_falsecolour() does implicit conversion

convert input automatically to mono 8-bit in falsecolour

ChangeLog

@@ -69,6 +69,7 @@
 - VIPS_EXEEXT is now part of the exported API
 - im_blend() also does sizealike, oops
 - jpeg write was not inverting CMYK, thanks Ole
+- im_falsecolour() converts to mono 8-bit for you
 
 30/11/10 started 7.24.0
 - bump for new stable

TODO

@@ -1,3 +1,9 @@
+- maplut should force to 8/16 bit unsigned? or does it?
+
+- im_vip2tiff() pyr builder should use new temp system
+
+- can isanalyze still add spurious messages to the vips error buffer?
+
 - icc import / export should cast their inputs, they insist on uchar/ushort at
   the moment
 
@@ -9,7 +15,9 @@
 
 
 
-- can we call vips7 funcs from the vips8 interface?
+- can we call vips7 funcs from the vips8 interface? we already have vips8 from
+  vips7
+
 
 
 - revisit orc conv

libvips/conversion/im_falsecolour.c

@@ -10,6 +10,8 @@
  * 29/1/10
  * 	- cleanups
  * 	- gtkdoc
+ * 12/7/11
+ * 	- force input to mono 8-bit for the user
  */
 
 /*
@@ -318,7 +320,8 @@ static unsigned char PET_colour[][3] = {
  * @in: input image
  * @out: output image
  *
- * Turn a 1-band 8-bit image into a 3-band 8-bit image with a false colour
+ * Force @in to 1 band, 8-bit, then transform to 
+ * 3-band 8-bit image with a false colour
  * map. The map is supposed to make small differences in brightness more
  * obvious.
  *
@@ -329,15 +332,18 @@ static unsigned char PET_colour[][3] = {
 int
 im_falsecolour( IMAGE *in, IMAGE *out )
 {
+	IMAGE *t[2];
 	IMAGE *lut;
 
-	/* Check our args. 
+	/* Check our args, force to mono 8-bit. 
 	 */
 	if( im_piocheck( in, out ) || 
-		im_check_mono( "im_falsecolour", in ) ||
-		im_check_uncoded( "im_falsecolour", in ) ||
-		im_check_format( "im_falsecolour", in, IM_BANDFMT_UCHAR ) )
+		im_check_uncoded( "im_falsecolour", in ) )
+		im_open_local_array( out, t, 2, "im_falsecolour", "p" ) ||
+		im_extract_band( in, t[0], 0 ) ||
+		im_clip2fmt( t[0], t[1], IM_BANDFMT_UCHAR ) 
 		return( -1 );
+	in = t[1];
 
 	if( !(lut = im_image( (PEL *) PET_colour, 
 		1, 256, 3, IM_BANDFMT_UCHAR )) )