fix(html): name a linked ooxml image relative to the document

CHANGELOG.md

@@ -16,6 +16,10 @@ The release run heads these entries with the version and opens a fresh
 
 ## Unreleased
 
+- A linked image in a docx or xlsx (`embed_images = false`) is named relative
+  to the document, like odf, so a host serving the html under a mount point
+  resolves it.
+
 ## v6.10.0 - 2026-08-20
 
 - Html views take a zoom from their host: `odr.getZoom()`, `setZoom(value,

src/odr/internal/html/document_element.cpp

@@ -5,6 +5,7 @@
 #include <odr/html.hpp>
 #include <odr/style.hpp>
 
+#include <odr/internal/common/path.hpp>
 #include <odr/internal/common/table_cursor.hpp>
 #include <odr/internal/html/common.hpp>
 #include <odr/internal/html/document_style.hpp>
@@ -498,9 +499,11 @@ void html::translate_image(const Element &element, const WritingState &state) {
   odr::HtmlResource resource;
   HtmlResourceLocation resource_location;
   if (image.is_internal()) {
-    resource =
-        HtmlResource::create(HtmlResourceType::image, "image/jpg", image.href(),
-                             image.href(), image.file(), false, false, true);
+    // the location is resolved against the document, so an engine naming the
+    // image by its absolute path in the container has to lose the root
+    const std::string path = Path(image.href()).make_relative().string();
+    resource = HtmlResource::create(HtmlResourceType::image, "image/jpg", path,
+                                    path, image.file(), false, false, true);
     resource_location =
         state.config().resource_locator(resource, state.config());
   } else {

test/src/html_test.cpp

@@ -7,6 +7,8 @@
 
 #include <odr/exceptions.hpp>
 
+#include <odr/internal/common/path.hpp>
+
 #include <internal/pdf/pdf_test_file_builder.hpp>
 
 #include <test_util.hpp>
@@ -64,6 +66,52 @@ TEST(html, linked_resources_are_served) {
       "document.html");
 }
 
+// Same for a document resource, which unlike a shipped one is named by the
+// engine: the reference output embeds every image, so nothing else renders the
+// linked form (opendocument-app/OpenDocument.droid#551).
+TEST(html, linked_images_are_served) {
+  const auto logger = Logger::create_stdio("odr-test", LogLevel::verbose);
+
+  const std::string cache_path =
+      (std::filesystem::current_path() / "images").string();
+
+  const auto check = [&](const std::string &path) {
+    const DecodedFile file(TestData::test_file_path(path), logger);
+
+    HtmlConfig config;
+    config.embed_images = false;
+
+    const HtmlService service = html::translate(file, cache_path, config);
+
+    std::ostringstream out;
+    const HtmlResources resources = service.list_views().at(0).write_html(out);
+
+    std::size_t linked = 0;
+    for (const auto &[resource, location] : resources) {
+      if (resource.type() != HtmlResourceType::image ||
+          !resource.is_accessible()) {
+        continue;
+      }
+      ASSERT_TRUE(location.has_value()) << resource.name();
+      ++linked;
+
+      // an absolute location would resolve against the server root rather than
+      // against the document
+      EXPECT_TRUE(Path(*location).relative()) << *location;
+      EXPECT_TRUE(service.exists(*location)) << *location;
+
+      std::ostringstream served;
+      service.write(*location, served);
+      EXPECT_FALSE(served.str().empty()) << *location;
+    }
+    EXPECT_GT(linked, 0) << path;
+  };
+
+  check("odr-public/odt/image-text-wrap.odt");
+  check("odr-public/docx/file-sample_100kB.docx");
+  check("odr-public/xlsx/sample.xlsx");
+}
+
 // The one archive the reference-output suite renders has no directory in it.
 // An archive may hold a file named like the stylesheet. Forcing the collision
 // through the locator saves needing such an archive in the test data.