text: add extended language property support

Author: bradh

examples/heif_info.cc

@@ -38,10 +38,12 @@
 #endif
 
 #include <libheif/heif.h>
+#include <libheif/heif_library.h>
 #include <libheif/heif_regions.h>
 #include <libheif/heif_properties.h>
 #include <libheif/heif_experimental.h>
 #include "libheif/heif_sequences.h"
+#include <libheif/heif_text.h>
 
 #include <fstream>
 #include <iostream>
@@ -639,6 +641,34 @@ int main(int argc, char** argv)
       printf("  none\n");
     }
 
+    // --- text items
+    int numTextItems = heif_image_handle_get_number_of_text_items(handle);
+    printf("text items:\n");
+
+    if (numTextItems > 0) {
+      std::vector<heif_item_id> text_items(numTextItems);
+      heif_image_handle_get_list_of_text_item_ids(handle, text_items.data(), numTextItems);
+      for (heif_item_id text_item_id : text_items) {
+        struct heif_text_item* text_item;
+        err = heif_context_get_text_item(ctx.get(), text_item_id, &text_item);
+        const char* text_content = heif_text_item_get_content(text_item);
+        printf("  text item: %s\n", text_content);
+        heif_string_release(text_content);
+
+        char* elng;
+        err = heif_item_get_property_extended_language(ctx.get(),
+                                                       text_item_id,
+                                                       &elng);
+        if (err.code == 0) {
+          printf("    extended language: %s\n", elng);
+        }
+        heif_string_release(elng);
+      }
+    }
+    else {
+      printf("  none\n");
+    }
+
     // --- properties
 
     printf("properties:\n");

libheif/Doxyfile.in

@@ -858,7 +858,8 @@ WARN_LOGFILE           =
 
 INPUT                  = @CMAKE_CURRENT_SOURCE_DIR@/libheif/api/libheif/heif.h \
 @CMAKE_CURRENT_SOURCE_DIR@/libheif/api/libheif/heif_items.h \
-@CMAKE_CURRENT_SOURCE_DIR@/libheif/api/libheif/heif_regions.h
+@CMAKE_CURRENT_SOURCE_DIR@/libheif/api/libheif/heif_regions.h \
+@CMAKE_CURRENT_SOURCE_DIR@/libheif/api/libheif/heif_text.h
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses

libheif/api/libheif/heif_properties.h

@@ -40,7 +40,8 @@ enum heif_item_property_type
   heif_item_property_type_image_size = heif_fourcc('i', 's', 'p', 'e'),
   heif_item_property_type_uuid = heif_fourcc('u', 'u', 'i', 'd'),
   heif_item_property_type_tai_clock_info = heif_fourcc('t', 'a', 'i', 'c'),
-  heif_item_property_type_tai_timestamp = heif_fourcc('i', 't', 'a', 'i')
+  heif_item_property_type_tai_timestamp = heif_fourcc('i', 't', 'a', 'i'),
+  heif_item_property_type_extended_language = heif_fourcc('e', 'l', 'n', 'g')
 };
 
 // Get the heif_property_id for a heif_item_id.

libheif/api/libheif/heif_text.cc

@@ -21,12 +21,14 @@
 
 #include "heif_text.h"
 #include "api_structs.h"
+#include "file.h"
 #include "text.h"
 #include <algorithm>
 #include <cstring>
 #include <memory>
-#include <utility>
 #include <string>
+#include <utility>
+#include <vector>
 
 struct heif_error heif_image_handle_add_text_item(heif_image_handle *image_handle,
                                            const char *content_type,
@@ -114,3 +116,49 @@ const char* heif_text_item_get_content(struct heif_text_item* text_item)
 
   return text_c;
 }
+
+struct heif_error heif_item_get_property_extended_language(const heif_context* context,
+                                                           heif_item_id itemId,
+                                                           char** out_language)
+{
+  if (!out_language || !context) {
+    return {heif_error_Usage_error, heif_suberror_Invalid_parameter_value, "NULL passed"};
+  }
+
+  auto elng = context->context->find_property<Box_elng>(itemId);
+  if (!elng) {
+    return elng.error_struct(context->context.get());
+  }
+
+  std::string lang = (*elng)->get_extended_language();
+  *out_language = new char[lang.length() + 1];
+  strcpy(*out_language, lang.c_str());
+
+  return heif_error_success;
+}
+
+struct heif_error heif_text_item_set_extended_language(heif_text_item* text_item, const char *language, heif_property_id* out_optional_propertyId)
+{
+  if (!text_item || !language) {
+    return {heif_error_Usage_error, heif_suberror_Null_pointer_argument, "NULL passed"};
+  }
+
+  if (auto img = text_item->context->get_image(text_item->text_item->get_item_id(), false)) {
+    auto existing_elng = img->get_property<Box_elng>();
+    if (existing_elng) {
+      existing_elng->set_lang(std::string(language));
+      return heif_error_success;
+    }
+  }
+
+  auto elng = std::make_shared<Box_elng>();
+  elng->set_lang(std::string(language));
+
+  heif_property_id id = text_item->context->add_property(text_item->text_item->get_item_id(), elng, false);
+
+  if (out_optional_propertyId) {
+    *out_optional_propertyId = id;
+  }
+
+  return heif_error_success;
+}

libheif/api/libheif/heif_text.h

@@ -85,7 +85,7 @@ heif_error heif_context_get_text_item(const heif_context* context,
 /**
  * Get the item identifier for a text item.
  *
- * @param region_item the text item to query
+ * @param text_item the text item to query
  * @return the text item identifier (or 0 if the text_item is null)
  */
 LIBHEIF_API
@@ -103,6 +103,19 @@ heif_item_id heif_text_item_get_id(heif_text_item* text_item);
 LIBHEIF_API
 const char* heif_text_item_get_content(heif_text_item* text_item);
 
+/**
+ * Get the extended language associated with the text item.
+ *
+ * @param context the context to get the text item from, usually from a file operation
+ * @param itemId the identifier for the text item
+ * @param out_language pointer to pointer to the resulting language
+ * @return heif_error_ok on success, or an error value indicating the problem
+ */
+LIBHEIF_API
+heif_error heif_item_get_property_extended_language(const heif_context* context,
+                                                    heif_item_id itemId,
+                                                    char** out_language);
+
 // --- adding text items
 
 /**
@@ -124,6 +137,22 @@ heif_error heif_image_handle_add_text_item(heif_image_handle *image_handle,
 LIBHEIF_API
 void heif_text_item_release(heif_text_item* text_item);
 
+/**
+ * Set the extended language property to the text item.
+ *
+ * This adds an RFC 5346 (IETF BCP 47) extended language tag, such as "en-AU".
+ *
+ * @param text_item the text item to query
+ * @param language the language to set
+ * @param out_optional_propertyId Output parameter for the property ID of the language property.
+ *                                This parameter may be NULL if the info is not required.
+ * @return heif_error_ok on success, or an error value indicating the problem
+ */
+LIBHEIF_API
+heif_error heif_text_item_set_extended_language(heif_text_item* text_item,
+                                                const char *language,
+                                                heif_property_id* out_optional_propertyId);
+
 #ifdef __cplusplus
 }
 #endif

libheif/box.cc

@@ -646,6 +646,11 @@ Error Box::read(BitstreamRange& range, std::shared_ptr<Box>* result, const heif_
       box = std::make_shared<Box_mjpg>();
       break;
 
+    case fourcc("elng"):
+      box = std::make_shared<Box_elng>();
+      break;
+
+
 #if WITH_UNCOMPRESSED_CODEC
     case fourcc("cmpd"):
       box = std::make_shared<Box_cmpd>();
@@ -4990,3 +4995,30 @@ Error Box_itai::parse(BitstreamRange& range, const heif_security_limits*) {
   return range.get_error();
 }
 
+Error Box_elng::parse(BitstreamRange& range, const heif_security_limits* limits)
+{
+  parse_full_box_header(range);
+
+  if (get_version() > 0) {
+    return unsupported_version_error("elng");
+  }
+
+  m_lang = range.read_string();
+  return range.get_error();
+}
+
+std::string Box_elng::dump(Indent& indent) const
+{
+  std::ostringstream sstr;
+  sstr << Box::dump(indent);
+  sstr << indent << "extended_language: " << m_lang << "\n";
+  return sstr.str();
+}
+
+Error Box_elng::write(StreamWriter& writer) const
+{
+  size_t box_start = reserve_box_header_space(writer);
+  writer.write(m_lang);
+  prepend_header(writer, box_start);
+  return Error::Ok;
+}

libheif/box.h

@@ -1818,4 +1818,51 @@ class Box_itai : public FullBox
 bool operator==(const heif_tai_timestamp_packet& a,
                 const heif_tai_timestamp_packet& b);
 
-#endif
+
+/**
+ * Extended language property.
+ *
+ * Permits the association of language information with an item.
+ *
+ * See ISO/IEC 23008-12:2025(E) Section 6.10.2.2 and ISO/IEC 14496-12:2022(E) Section 8.4.6.
+ */
+class Box_elng : public FullBox
+{
+public:
+  Box_elng()
+  {
+    set_short_type(fourcc("elng"));
+  }
+
+  std::string dump(Indent&) const override;
+
+  const char* debug_box_name() const override { return "Extended language"; }
+
+  Error write(StreamWriter& writer) const override;
+
+  /**
+   * Language.
+   *
+   * An RFC 5646 (IETF BCP 47) compliant language identifier for the language of the text.
+   * Examples: "en-AU", "de-DE", or "zh-CN“.
+   */
+  std::string get_extended_language() const { return m_lang; }
+
+  /**
+   * Set the language.
+   *
+   * An RFC 5646 (IETF BCP 47) compliant language identifier for the language of the text.
+   * Examples: "en-AU", "de-DE", or "zh-CN“.
+   */
+  void set_lang(const std::string lang) { m_lang = lang; }
+
+  [[nodiscard]] parse_error_fatality get_parse_error_fatality() const override { return parse_error_fatality::optional; }
+
+protected:
+  Error parse(BitstreamRange& range, const heif_security_limits*) override;
+
+private:
+  std::string m_lang;
+};
+
+#endif

tests/text.cc

@@ -33,6 +33,7 @@
 #include <cstdint>
 #include <cstring>
 #include <libheif/heif_items.h>
+#include <libheif/heif_library.h>
 
 
 TEST_CASE("no text") {
@@ -83,11 +84,17 @@ TEST_CASE("create text item") {
   std::string text_body1("first string");
   err = heif_image_handle_add_text_item(handle, "text/plain", text_body1.c_str(), &text_item1);
   REQUIRE(err.code == heif_error_Ok);
+  err = heif_text_item_set_extended_language(text_item1, "en-AU", NULL);
+  REQUIRE(err.code == heif_error_Ok);
 
   struct heif_text_item* text_item2;
   std::string text_body2("a second string");
   err = heif_image_handle_add_text_item(handle, "text/plain", text_body2.c_str(), &text_item2);
   REQUIRE(err.code == heif_error_Ok);
+  heif_property_id elng_prop_id;
+  err = heif_text_item_set_extended_language(text_item2, "en-UK", &elng_prop_id);
+  REQUIRE(err.code == heif_error_Ok);
+  REQUIRE(elng_prop_id != 0);
 
   err = heif_context_write_to_file(ctx, "text.heif");
   REQUIRE(err.code == heif_error_Ok);
@@ -128,6 +135,12 @@ TEST_CASE("create text item") {
   REQUIRE(std::string(content_type0) == "text/plain");
   const char* body0 = heif_text_item_get_content(text0);
   REQUIRE(std::string(body0) == text_body1);
+  heif_string_release(body0);
+  char * elng0;
+  err = heif_item_get_property_extended_language(readbackCtx, id0, &elng0);
+  REQUIRE(err.code == heif_error_Ok);
+  REQUIRE(strcmp(elng0, "en-AU") == 0);
+  heif_string_release(elng0);
 
   heif_text_item* text1;
   err = heif_context_get_text_item(readbackCtx, text_item_ids[1], &text1);
@@ -139,6 +152,12 @@ TEST_CASE("create text item") {
   REQUIRE(std::string(content_type1) == "text/plain");
   const char* body1 = heif_text_item_get_content(text1);
   REQUIRE(std::string(body1) == text_body2);
+  heif_string_release(body1);
+  char * elng1;
+  err = heif_item_get_property_extended_language(readbackCtx, id1, &elng1);
+  REQUIRE(err.code == heif_error_Ok);
+  REQUIRE(strcmp(elng1, "en-UK") == 0);
+  heif_string_release(elng1);
 
   heif_text_item_release(text0);
   heif_text_item_release(text1);