Revert vips_embed() change

libvips/resample/shrinkv.c

@@ -345,9 +345,7 @@ vips_shrinkv_uchar_vector_gen(VipsRegion *out_region,
 		s.left = r->left;
 		s.top = (r->top + y) * shrink->vshrink;
 		s.width = r->width;
-		/* Needs to access an additional `vshrink` scanlines.
-		 */
-		s.height = chunk_height * shrink->vshrink + shrink->vshrink;
+		s.height = chunk_height * shrink->vshrink;
 #ifdef DEBUG
 		printf("vips_shrinkv_uchar_vector_gen: requesting %d lines from %d\n",
 			s.height, s.top);
@@ -402,12 +400,12 @@ vips_shrinkv_build(VipsObject *object)
 	if (shrink->vshrink == 1)
 		return vips_image_write(in, resample->out);
 
-	/* We need new pixels along the bottom so that we don't have small chunks
-	 * to average along the bottom edge.
+	/* Make the height a multiple of the shrink factor so we don't need to
+	 * average half pixels.
 	 */
 	if (vips_embed(in, &t[1],
 			0, 0,
-			in->Xsize, in->Ysize + shrink->vshrink,
+			in->Xsize, VIPS_ROUND_UP(in->Ysize, shrink->vshrink),
 			"extend", VIPS_EXTEND_COPY,
 			NULL))
 		return -1;