diff --git a/src/cpp/writer/tswriter.cpp b/src/cpp/writer/tswriter.cpp
index 198cd18..121ecd0 100644
--- a/src/cpp/writer/tswriter.cpp
+++ b/src/cpp/writer/tswriter.cpp
@@ -70,7 +70,7 @@ TsWriterCPP::TsWriterCPP(
 }
 
 void TsWriterCPP::WriteImageData(
-    py::array& py_image,
+    const py::array& py_image,
     const Seq& rows,
     const Seq& cols,
     const std::optional<Seq>& layers,
@@ -108,7 +108,7 @@ void TsWriterCPP::WriteImageData(
     switch(_dtype_code)
     {
         case (1): {
-            auto data_array = tensorstore::Array(py_image.mutable_unchecked<std::uint8_t, 1>().data(0), shape, tensorstore::c_order);
+            auto data_array = tensorstore::Array(py_image.unchecked<std::uint8_t, 1>().data(0), shape, tensorstore::c_order);
 
             // Write data array to TensorStore
             auto write_result = tensorstore::Write(tensorstore::UnownedToShared(data_array), _source | output_transform).result();
@@ -120,7 +120,7 @@ void TsWriterCPP::WriteImageData(
             break;
         }
         case (2): {
-            auto data_array = tensorstore::Array(py_image.mutable_unchecked<std::uint16_t, 1>().data(0), shape, tensorstore::c_order);
+            auto data_array = tensorstore::Array(py_image.unchecked<std::uint16_t, 1>().data(0), shape, tensorstore::c_order);
 
             auto write_result = tensorstore::Write(tensorstore::UnownedToShared(data_array), _source | output_transform).result();
             if (!write_result.ok()) {
@@ -129,7 +129,7 @@ void TsWriterCPP::WriteImageData(
             break;
         }
         case (4): {
-            auto data_array = tensorstore::Array(py_image.mutable_unchecked<std::uint32_t, 1>().data(0), shape, tensorstore::c_order);
+            auto data_array = tensorstore::Array(py_image.unchecked<std::uint32_t, 1>().data(0), shape, tensorstore::c_order);
 
             auto write_result = tensorstore::Write(tensorstore::UnownedToShared(data_array), _source | output_transform).result();
             if (!write_result.ok()) {
@@ -138,7 +138,7 @@ void TsWriterCPP::WriteImageData(
             break;
         }
         case (8): {
-            auto data_array = tensorstore::Array(py_image.mutable_unchecked<std::uint64_t, 1>().data(0), shape, tensorstore::c_order);
+            auto data_array = tensorstore::Array(py_image.unchecked<std::uint64_t, 1>().data(0), shape, tensorstore::c_order);
 
             auto write_result = tensorstore::Write(tensorstore::UnownedToShared(data_array), _source | output_transform).result();
             if (!write_result.ok()) {
@@ -147,7 +147,7 @@ void TsWriterCPP::WriteImageData(
             break;
         }
         case (16): {
-            auto data_array = tensorstore::Array(py_image.mutable_unchecked<std::int8_t, 1>().data(0), shape, tensorstore::c_order);
+            auto data_array = tensorstore::Array(py_image.unchecked<std::int8_t, 1>().data(0), shape, tensorstore::c_order);
 
             auto write_result = tensorstore::Write(tensorstore::UnownedToShared(data_array), _source | output_transform).result();
             if (!write_result.ok()) {
@@ -156,7 +156,7 @@ void TsWriterCPP::WriteImageData(
             break;
         }
         case (32): {
-            auto data_array = tensorstore::Array(py_image.mutable_unchecked<std::int16_t, 1>().data(0), shape, tensorstore::c_order);
+            auto data_array = tensorstore::Array(py_image.unchecked<std::int16_t, 1>().data(0), shape, tensorstore::c_order);
 
             auto write_result = tensorstore::Write(tensorstore::UnownedToShared(data_array), _source | output_transform).result();
             if (!write_result.ok()) {
@@ -165,7 +165,7 @@ void TsWriterCPP::WriteImageData(
             break;
         }
         case (64): {
-            auto data_array = tensorstore::Array(py_image.mutable_unchecked<std::int32_t, 1>().data(0), shape, tensorstore::c_order);
+            auto data_array = tensorstore::Array(py_image.unchecked<std::int32_t, 1>().data(0), shape, tensorstore::c_order);
 
             auto write_result = tensorstore::Write(tensorstore::UnownedToShared(data_array), _source | output_transform).result();
             if (!write_result.ok()) {
@@ -174,7 +174,7 @@ void TsWriterCPP::WriteImageData(
             break;
         }
         case (128): {
-            auto data_array = tensorstore::Array(py_image.mutable_unchecked<std::int64_t, 1>().data(0), shape, tensorstore::c_order);
+            auto data_array = tensorstore::Array(py_image.unchecked<std::int64_t, 1>().data(0), shape, tensorstore::c_order);
 
             // Write data array to TensorStore
             auto write_result = tensorstore::Write(tensorstore::UnownedToShared(data_array), _source | output_transform).result();
@@ -184,7 +184,7 @@ void TsWriterCPP::WriteImageData(
             break;
         }
         case (256): {
-            auto data_array = tensorstore::Array(py_image.mutable_unchecked<float, 1>().data(0), shape, tensorstore::c_order);
+            auto data_array = tensorstore::Array(py_image.unchecked<float, 1>().data(0), shape, tensorstore::c_order);
 
             auto write_result = tensorstore::Write(tensorstore::UnownedToShared(data_array), _source | output_transform).result();
             if (!write_result.ok()) {
@@ -193,7 +193,7 @@ void TsWriterCPP::WriteImageData(
             break;
         }
         case (512): {
-            auto data_array = tensorstore::Array(py_image.mutable_unchecked<double, 1>().data(0), shape, tensorstore::c_order);
+            auto data_array = tensorstore::Array(py_image.unchecked<double, 1>().data(0), shape, tensorstore::c_order);
 
             auto write_result = tensorstore::Write(tensorstore::UnownedToShared(data_array), _source | output_transform).result();
             if (!write_result.ok()) {
diff --git a/src/cpp/writer/tswriter.h b/src/cpp/writer/tswriter.h
index 92dbaa8..98130a4 100644
--- a/src/cpp/writer/tswriter.h
+++ b/src/cpp/writer/tswriter.h
@@ -21,7 +21,7 @@ class TsWriterCPP{
     );
 
     void WriteImageData (
-        py::array& py_image, 
+        const py::array& py_image, 
         const Seq& rows, 
         const Seq& cols, 
         const std::optional<Seq>& layers, 
diff --git a/src/python/bfiocpp/tsreader.py b/src/python/bfiocpp/tsreader.py
index 0d76ad7..ac7ad63 100644
--- a/src/python/bfiocpp/tsreader.py
+++ b/src/python/bfiocpp/tsreader.py
@@ -18,7 +18,7 @@ def __init__(self, file_name: str, file_type: FileType, axes_list: str) -> None:
         self._filetype = file_type
 
     def data(
-        self, rows: int, cols: int, layers: int, channels: int, tsteps: int
+        self, rows: Seq, cols: Seq, layers: Seq, channels: Seq, tsteps: Seq
     ) -> np.ndarray:
         return self._image_reader.get_image_data(rows, cols, layers, channels, tsteps)