fix icc-profiles and dzsave --no-strip

We were not copying metadata down pyramid layers in dzsave, so
--no-strip didn't allow icc profiles on tiles.

Thanks altert

See https://github.com/libvips/libvips/issues/1879

ChangeLog

@@ -6,6 +6,7 @@
 - fix tiffsave region shrink mode [imgifty]
 - add missing flushes on write to target [harukizaemon]
 - hide info messages you could get with some older glibs [kleisauke]
+- fix --no-strip on dzsave with icc-profiles [altert]
 
 6/9/20 started 8.10.2
 - update magicksave/load profile handling [kelilevi]

libvips/foreign/dzsave.c

@@ -613,8 +613,8 @@ write_image( VipsForeignSaveDz *dz,
 	if( vips_copy( image, &t, NULL ) ) 
 		return( -1 );
 
-	/* We default to stripping all metadata. Only "no_strip" turns this
-	 * off. Very few people really want metadata on every tile.
+	/* We default to stripping all metadata. "no_strip" turns this
+	 * off. Most people don't want metadata on every tile.
 	 */
 	vips_image_set_int( t, "hide-progress", 1 );
 	if( vips_image_write_to_buffer( t, format, &buf, &len,
@@ -1312,6 +1312,13 @@ strip_init( Strip *strip, Layer *layer )
 		return;
 	}
 
+	/* The strip needs to inherit the layer's metadata.
+	 */
+	if( vips__image_meta_copy( strip->image, layer->image ) ) {
+		strip_free( strip );
+		return;
+	}
+
 	/* Type needs to be set so we know how to convert for save correctly.
 	 */
 	strip->image->Type = layer->image->Type;

libvips/include/vips/internal.h

@@ -152,6 +152,7 @@ int vips__write_extension_block( VipsImage *im, void *buf, int size );
 int vips__writehist( VipsImage *image );
 int vips__read_header_bytes( VipsImage *im, unsigned char *from );
 int vips__write_header_bytes( VipsImage *im, unsigned char *to );
+int vips__image_meta_copy( VipsImage *dst, const VipsImage *src );
 
 extern GMutex *vips__global_lock;
 

libvips/iofuncs/header.c

@@ -994,8 +994,8 @@ meta_cp_field( VipsMeta *meta, VipsImage *dst, void *b )
 
 /* Copy meta on to dst. 
  */
-static int
-meta_cp( VipsImage *dst, const VipsImage *src )
+int
+vips__image_meta_copy( VipsImage *dst, const VipsImage *src )
 {
 	if( src->meta ) {
 		/* We lock with vips_image_set() to stop races in highly-
@@ -1051,7 +1051,7 @@ vips__image_copy_fields_array( VipsImage *out, VipsImage *in[] )
 	 * subclass loaders will sometimes write to an image. 
 	 */
 	for( i = ni - 1; i >= 0; i-- ) 
-		if( meta_cp( out, in[i] ) )
+		if( vips__image_meta_copy( out, in[i] ) )
 			return( -1 );
 
 	/* Merge hists first to last.
@@ -1094,7 +1094,7 @@ vips_image_set( VipsImage *image, const char *name, GValue *value )
 	g_assert( value );
 
 	/* We lock between modifying metadata and copying metadata between
-	 * images, see meta_cp().
+	 * images, see vips__image_meta_copy().
 	 *
 	 * This prevents modification of metadata by one thread racing with
 	 * metadata copy on another -- this can lead to crashes in
@@ -1302,7 +1302,7 @@ vips_image_remove( VipsImage *image, const char *name )
 
 	if( image->meta ) {
 		/* We lock between modifying metadata and copying metadata 
-		 * between images, see meta_cp().
+		 * between images, see vips__image_meta_copy().
 		 *
 		 * This prevents modification of metadata by one thread 
 		 * racing with metadata copy on another -- this can lead to 

test/test-suite/test_foreign.py

@@ -1026,6 +1026,13 @@ class TestForeign:
         buf = self.colour.dzsave_buffer(region_shrink="mode")
         buf = self.colour.dzsave_buffer(region_shrink="median")
 
+        # test no-strip ... icc profiles should be passed down
+        filename = temp_filename(self.tempdir, '')
+        self.colour.dzsave(filename, no_strip=True)
+
+        y = pyvips.Image.new_from_file(filename + "_files/0/0_0.jpeg")
+        assert y.get_typeof("icc-profile-data") != 0
+
     @skip_if_no("heifload")
     def test_heifload(self):
         def heif_valid(im):