fix vipsthumbnail with broken embedded profiles

if the embedded profile is broken or incompatible with the specified
output profile, retry with the specified input profile

see

https://github.com/jcupitt/libvips/issues/178

ChangeLog

@@ -3,6 +3,8 @@
 - support GRAY as an input and output ICC space
 - fix a read loop with setjmp() in png read, if the png file is broken
 - fix vipsthumbnail with both input cmyk and output rgb profiles specified
+- vipsthumbnail retries with specified input profile if embedded profile is
+  broken
 
 8/9/14 started 7.40.8
 - fix configure on rhel6 [Lovell]

tools/vipsthumbnail.c

@@ -58,6 +58,9 @@
  * 	- add an anti-alias filter between shrink and affine
  * 	- support CMYK
  * 	- use SEQ_UNBUF for a memory saving
+ * 12/9/14
+ * 	- try with embedded profile first, if that fails retry with fallback
+ * 	  profile
  */
 
 #ifdef HAVE_CONFIG_H
@@ -567,23 +570,48 @@ thumbnail_shrink( VipsObject *process, VipsImage *in,
 	else if( export_profile &&
 		(vips_image_get_typeof( in, VIPS_META_ICC_NAME ) || 
 		 import_profile) ) {
-		if( vips_image_get_typeof( in, VIPS_META_ICC_NAME ) )
-			vips_info( "vipsthumbnail", 
-				"importing with embedded profile" );
-		else
-			vips_info( "vipsthumbnail", 
-				"importing with profile %s", import_profile );
+		VipsImage *out;
 
 		vips_info( "vipsthumbnail", 
 			"exporting with profile %s", export_profile );
 
-		if( vips_icc_transform( in, &t[7], export_profile,
-			"input_profile", import_profile,
-			"embedded", TRUE,
-			NULL ) )  
-			return( NULL );
+		/* We first try with the embedded profile, if any, then if
+		 * that fails try again with the supplied fallback profile.
+		 */
+		out = NULL; 
+		if( vips_image_get_typeof( in, VIPS_META_ICC_NAME ) ) {
+			vips_info( "vipsthumbnail", 
+				"importing with embedded profile" );
 
-		in = t[7];
+			if( vips_icc_transform( in, &t[7], export_profile,
+				"embedded", TRUE,
+				NULL ) ) {
+				vips_warn( "vipsthumbnail", 
+					_( "unable to import with "
+						"embedded profile: %s" ),
+					vips_error_buffer() );
+
+				vips_error_clear();
+			}
+			else
+				out = t[7];
+		}
+
+		if( !out &&
+			import_profile ) { 
+			vips_info( "vipsthumbnail", 
+				"importing with fallback profile" );
+
+			if( vips_icc_transform( in, &t[7], export_profile,
+				"input_profile", import_profile,
+				"embedded", FALSE,
+				NULL ) )  
+				return( NULL );
+
+			out = t[7];
+		}
+
+		in = out;
 	}
 
 	/* If we are upsampling, don't sharpen, since nearest looks dumb