add heif_context_set_major_brand() to set user-defined major brand

Author: farindk

libheif/api/libheif/heif_encoding.cc

@@ -767,6 +767,15 @@ struct heif_error heif_context_set_primary_image(struct heif_context* ctx,
 }
 
 
+void heif_context_set_major_brand(struct heif_context* ctx,
+                                  heif_brand2 major_brand)
+{
+  auto ftyp = ctx->context->get_heif_file()->get_ftyp_box();
+  ftyp->set_major_brand(major_brand);
+  ftyp->add_compatible_brand(major_brand);
+}
+
+
 void heif_context_add_compatible_brand(struct heif_context* ctx,
                                        heif_brand2 compatible_brand)
 {

libheif/api/libheif/heif_encoding.h

@@ -348,6 +348,13 @@ LIBHEIF_API
 struct heif_error heif_context_set_primary_image(struct heif_context*,
                                                  struct heif_image_handle* image_handle);
 
+// Set the major brand of the file.
+// If this function is not called, the major brand is determined automatically from
+// the image or sequence content.
+LIBHEIF_API
+void heif_context_set_major_brand(struct heif_context* ctx,
+                                  heif_brand2 major_brand);
+
 // Add a compatible brand that is now added automatically by libheif when encoding images (e.g. some application brands like 'geo1').
 LIBHEIF_API
 void heif_context_add_compatible_brand(struct heif_context* ctx,

libheif/api/libheif/heif_experimental.cc

@@ -500,4 +500,3 @@ struct heif_error heif_context_add_tiled_image(struct heif_context* ctx,
   return heif_error_success;
 }
 #endif
-

libheif/api/libheif/heif_experimental.h

@@ -315,7 +315,6 @@ struct heif_complex64* heif_image_get_channel_complex64(struct heif_image*,
                                                         size_t* out_stride);
 #endif
 
-
 #ifdef __cplusplus
 }
 #endif

libheif/context.cc

@@ -371,7 +371,12 @@ void HeifContext::write(StreamWriter& writer)
   // See https://github.com/strukturag/libheif/issues/478
 
   auto ftyp = m_heif_file->get_ftyp_box();
-  ftyp->set_major_brand(main_brand);
+
+  // set major brand if not set manually yet
+  if (ftyp->get_major_brand() == 0) {
+    ftyp->set_major_brand(main_brand);
+  }
+
   ftyp->set_minor_version(0);
   for (auto brand : compatible_brands) {
     ftyp->add_compatible_brand(brand);