cast to unsigned int did not remove <0

previously cast to uint did nothing (since the positive range of uint is
greater than int), now it changes <0 values to 0

ChangeLog

@@ -3,6 +3,7 @@
 - fix warning for unused vips7 gvalue argument
 - fix openslide read: always return png-style rgba, im_argb2rgba() becomes a
   NOP
+- cast to unsigned int now removes <0 values
 
 13/3/12 started 7.28.2
 - xres/yres tiffsave args were broken

libvips/conversion/cast.c

@@ -45,6 +45,8 @@
  * 	- gtk-doc
  * 27/10/11
  * 	- redone as a class
+ * 10/4/12
+ * 	- cast to uint now removes <0 values
  */
 
 /*
@@ -288,7 +290,7 @@ vips_cast_start( VipsImage *out, void *a, void *b )
 		break; \
 	\
 	case VIPS_FORMAT_UINT: \
-		INT( ITYPE, unsigned int, VIPS_CLIP_NONE ); \
+		INT( ITYPE, unsigned int, VIPS_CLIP_UINT ); \
 		break; \
 	\
 	case VIPS_FORMAT_INT: \

libvips/include/vips/util.h

@@ -146,6 +146,14 @@ G_STMT_START { \
 	}  \
 } G_STMT_END
 
+#define VIPS_CLIP_UINT( V, SEQ ) \
+G_STMT_START { \
+	if( (V) < 0 ) {   \
+		(SEQ)->underflow++;   \
+		(V) = 0;   \
+	}  \
+} G_STMT_END
+
 #define VIPS_CLIP_NONE( V, SEQ ) {}
 
 const char *vips_enum_string( GType enm, int value );