much faster RGB16 -> sRGB path

ChangeLog

@@ -18,6 +18,7 @@
 - add lower-level operation cache access
 - turn on leak testing in test suite
 - don't use isnormal() to test for crazy FP numbers, thanks Murat
+- much faster RGB16 -> sRGB path
 
 24/12/14 started 7.42.1
 - add gobject-2.0 to Requires: in vips and vips-cpp .pc files

TODO

@@ -1,5 +1,3 @@
-
-
 - use vips_resize() in vipsthumbnail?
 
   should the sharpening filter be selectable?
@@ -24,8 +22,6 @@
 
 - fix up aconv
 
-- more python tests
-
 - can we pick the vipsthumbnail int shrink factor more intelligently?
 
 - rewrite im_conv() etc. as vips_conv(), also the mosaicing functions

libvips/colour/colourspace.c

@@ -14,6 +14,8 @@
  * 	- oops, don't treat RGB16 as sRGB
  * 9/9/14	
  * 	- mono <-> rgb converters were not handling extra bands, thanks James
+ * 4/2/15
+ * 	- much faster RGB16->sRGB path
  */
 
 /*
@@ -71,6 +73,17 @@ vips_scRGB2RGB16( VipsImage *in, VipsImage **out, ... )
 	return( vips_scRGB2sRGB( in, out, "depth", 16, NULL ) );
 }
 
+static int
+vips_RGB162sRGB( VipsImage *in, VipsImage **out, ... )
+{
+	if( vips_msb( in, out, NULL ) )
+		return( -1 );
+
+	(*out)->Type = VIPS_INTERPRETATION_sRGB;
+
+	return( 0 ); 
+}
+
 /* Process the first @n bands with @fn, detach and reattach remaining bands.
  */
 static int
@@ -335,8 +348,8 @@ static VipsColourRoute vips_colour_routes[] = {
 	{ RGB16, CMC, { vips_sRGB2scRGB, vips_scRGB2XYZ, vips_XYZ2Lab, 
 		vips_Lab2LCh, vips_LCh2CMC, NULL } },
 	{ RGB16, scRGB, { vips_sRGB2scRGB, NULL } },
-	{ RGB16, sRGB, { vips_sRGB2scRGB, vips_scRGB2sRGB, NULL } },
-	{ RGB16, BW, { vips_sRGB2scRGB, vips_scRGB2sRGB, vips_sRGB2BW, NULL } },
+	{ RGB16, sRGB, { vips_RGB162sRGB, NULL } },
+	{ RGB16, BW, { vips_RGB162sRGB, vips_sRGB2BW, NULL } },
 	{ RGB16, LABS, { vips_sRGB2scRGB, vips_scRGB2XYZ, vips_XYZ2Lab, 
 		vips_Lab2LabS, NULL } },
 	{ RGB16, GREY16, { vips_RGB162GREY16, NULL } },