From 1177bd1dae4ba5fce7a5917ecb74d8cd33c598ef Mon Sep 17 00:00:00 2001
From: Lovell Fuller <github@lovell.info>
Date: Fri, 9 Oct 2020 15:54:17 +0100
Subject: [PATCH] heifload: expose heif-compression metadata

---
 configure.ac               | 12 ++++++++++++
 libvips/foreign/heifload.c | 20 ++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/configure.ac b/configure.ac
index 71aa97a6..891bce12 100644
--- a/configure.ac
+++ b/configure.ac
@@ -888,6 +888,18 @@ if test x"$with_heif" = x"yes"; then
   LIBS="$save_LIBS"
 fi
 
+# heif_main_brand added in 1.4.0
+if test x"$with_heif" = x"yes"; then
+  save_LIBS="$LIBS"
+  LIBS="$LIBS $HEIF_LIBS"
+  AC_CHECK_FUNCS(heif_main_brand,[
+     AC_DEFINE(HAVE_HEIF_MAIN_BRAND,1,
+	       [define if you have heif_main_brand.])
+   ],[]
+  )
+  LIBS="$save_LIBS"
+fi
+
 # heif_decoding_options.convert_hdr_to_8bit added in 1.7.0
 if test x"$with_heif" = x"yes"; then
   save_CFLAGS="$CFLAGS"
diff --git a/libvips/foreign/heifload.c b/libvips/foreign/heifload.c
index 802fdc66..ca95e2f7 100644
--- a/libvips/foreign/heifload.c
+++ b/libvips/foreign/heifload.c
@@ -420,6 +420,7 @@ vips_foreign_load_heif_set_header( VipsForeignLoadHeif *heif, VipsImage *out )
 	heif_item_id id[16];
 	int n_metadata;
 	struct heif_error error;
+	VipsForeignHeifCompression compression;
 
 	/* We take the metadata from the non-thumbnail first page. HEIC 
 	 * thumbnails don't have metadata.
@@ -566,6 +567,25 @@ vips_foreign_load_heif_set_header( VipsForeignLoadHeif *heif, VipsImage *out )
 		vips_image_set_int( out, 
 			VIPS_META_PAGE_HEIGHT, heif->page_height );
 
+	/* Determine compression from HEIF "brand"
+	 * Requires libheif 1.4.0+, prior versions were HEVC only
+	 */
+	compression = VIPS_FOREIGN_HEIF_COMPRESSION_HEVC;
+
+#ifdef HAVE_HEIF_MAIN_BRAND
+	const unsigned char *brand_data;
+	if ( brand_data = vips_source_sniff( heif->source, 12 ) ) {
+		enum heif_brand brand;
+		brand = heif_main_brand( brand_data, 12 );
+		if( brand == heif_avif || brand == heif_avis )
+			compression = VIPS_FOREIGN_HEIF_COMPRESSION_AV1;
+	}
+#endif /*HAVE_HEIF_MAIN_BRAND*/
+
+	vips_image_set_string( out, "heif-compression",
+		vips_enum_nick( VIPS_TYPE_FOREIGN_HEIF_COMPRESSION,
+			compression ) );
+
 	/* FIXME .. we always decode to RGB in generate. We should check for
 	 * all grey images, perhaps. 
 	 */