Fix inaccurate reporting of append dimension size in metadata. (#286)

I noticed an issue where the shape of the array in the final dimension
was always reported as the number of frames acquired, which, in the case
of nontrivial internal dimensions, is just wrong. Opening up such a
dataset in napari will confirm.

---------

Co-authored-by: Justin Eskesen <jeskesen@chanzuckerberg.com>

src/writers/zarrv2.array.writer.cpp

@@ -122,7 +122,15 @@ zarr::ZarrV2ArrayWriter::write_array_metadata_()
 
     std::vector<size_t> array_shape, chunk_shape;
 
-    array_shape.push_back(frames_written_);
+    size_t append_size = frames_written_;
+    for (auto dim = config_.dimensions.begin() + 2;
+         dim < config_.dimensions.end() - 1;
+         ++dim) {
+        CHECK(dim->array_size_px);
+        append_size = (append_size + dim->array_size_px - 1) / dim->array_size_px;
+    }
+    array_shape.push_back(append_size);
+
     chunk_shape.push_back(config_.dimensions.back().chunk_size_px);
     for (auto dim = config_.dimensions.rbegin() + 1;
          dim != config_.dimensions.rend();

src/writers/zarrv3.array.writer.cpp

@@ -176,7 +176,15 @@ zarr::ZarrV3ArrayWriter::write_array_metadata_()
 
     std::vector<size_t> array_shape, chunk_shape, shard_shape;
 
-    array_shape.push_back(frames_written_);
+    size_t append_size = frames_written_;
+    for (auto dim = config_.dimensions.begin() + 2;
+         dim < config_.dimensions.end() - 1;
+         ++dim) {
+        CHECK(dim->array_size_px);
+        append_size = (append_size + dim->array_size_px - 1) / dim->array_size_px;
+    }
+    array_shape.push_back(append_size);
+
     chunk_shape.push_back(config_.dimensions.back().chunk_size_px);
     shard_shape.push_back(config_.dimensions.back().shard_size_chunks);
     for (auto dim = config_.dimensions.rbegin() + 1;

tests/CMakeLists.txt

@@ -22,6 +22,7 @@ else ()
             external-metadata-with-whitespace-ok
             restart-stopped-zarr-resets-threadpool
             repeat-start
+            metadata-dimension-sizes
             write-zarr-v2-raw
             write-zarr-v2-raw-chunk-size-larger-than-frame-size
             write-zarr-v2-raw-with-even-chunking