diff --git a/.vscode/c_cpp_properties.json b/.vscode/c_cpp_properties.json
index 930311e..67bb44b 100644
--- a/.vscode/c_cpp_properties.json
+++ b/.vscode/c_cpp_properties.json
@@ -3,7 +3,10 @@
         {
             "name": "Linux",
             "includePath": [
-                "${workspaceFolder}/**",
+                "${workspaceFolder}/file_io/**",
+                "${workspaceFolder}/core/**",
+                "${workspaceFolder}/tests/**",
+                "${workspaceFolder}/tests/**",
                 "/usr/include"
             ],
             "defines": [],
diff --git a/CMakeLists.txt b/CMakeLists.txt
index b6fbd68..76ccfa1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -17,7 +17,7 @@ include(GNUInstallDirs)
 include(FetchContent)
 
 
-option(AARE_USE_WARNINGS "Eable warnings" ON)
+option(AARE_USE_WARNINGS "Eable warnings" OFF)
 option(AARE_PYTHON_BINDINGS "Build python bindings" ON)
 option(AARE_TESTS "Build tests" ON)
 option(AARE_EXAMPLES "Build examples" ON)
diff --git a/core/include/aare/Frame.hpp b/core/include/aare/Frame.hpp
index 78918a6..b19689a 100644
--- a/core/include/aare/Frame.hpp
+++ b/core/include/aare/Frame.hpp
@@ -22,6 +22,7 @@ template <class DataType> class Frame{
     ssize_t cols;
     DataType* data;
     ssize_t bitdepth = sizeof(DataType)*8;
+    Frame(ssize_t rows, ssize_t cols);
 
     Frame(std::byte* fp, ssize_t rows, ssize_t cols);
     DataType get(int row, int col);
diff --git a/core/src/Frame.cpp b/core/src/Frame.cpp
index f035fc4..8bed03d 100644
--- a/core/src/Frame.cpp
+++ b/core/src/Frame.cpp
@@ -8,13 +8,18 @@ Frame<DataType>::Frame(std::byte* bytes, ssize_t rows, ssize_t cols):
     std::memcpy(data, bytes, rows*cols*sizeof(DataType));
   }
 
+template <typename DataType>
+Frame<DataType>::Frame(ssize_t rows, ssize_t cols):
+  rows(rows), cols(cols) {
+    data = new DataType[rows*cols];
+  }
+
 
 
 template <typename DataType>
 DataType Frame<DataType>::get(int row, int col) {
   if (row < 0 || row >= rows || col < 0 || col >= cols) {
-    std::cerr << "Invalid row or column index" << std::endl;
-    return 0;
+    throw std::runtime_error("Invalid row or column index");
   }
   return data[row*cols + col];
 }
diff --git a/data/test_numpy_file.npy b/data/test_numpy_file.npy
new file mode 100644
index 0000000..ca1bc7e
Binary files /dev/null and b/data/test_numpy_file.npy differ
diff --git a/examples/main.cpp b/examples/main.cpp
index f4d45cb..66d8af5 100644
--- a/examples/main.cpp
+++ b/examples/main.cpp
@@ -1,25 +1,30 @@
 // Your First C++ Program
-#include <iostream>
 #include "aare/FileHandler.hpp"
+#include <iostream>
 
-using JFileHandler = FileHandler<DetectorType::Jungfrau,uint16_t>;
-using JFile = File<DetectorType::Jungfrau,uint16_t>;
+using JFileHandler = FileHandler<DetectorType::Jungfrau, uint16_t>;
+using JFile = File<DetectorType::Jungfrau, uint16_t>;
 using JFrame = Frame<uint16_t>;
 
-
-void test(JFileHandler* f,int frame_number){
+void test(JFileHandler *f, int frame_number) {
     std::cout << "frame number: " << frame_number << std::endl;
-    JFrame* frame = f->get_frame(frame_number);
-    std::cout << frame->get(0,0) << ' ';
-    std::cout << frame->get(0,1) << ' ';
-    std::cout << frame->get(1,0) << ' ';
-    std::cout << frame->get(511,1023) << std::endl;
+    JFrame *frame = f->get_frame(frame_number);
+    std::cout << frame->get(0, 0) << std::endl;
+    std::cout << frame->get(0, 1) << std::endl;
+    std::cout << frame->get(1, 0) << std::endl;
+    std::cout << frame->get(49, 49) << std::endl;
 
     delete frame;
 }
 
 int main() {
-    std::filesystem::path fpath("/home/bb/github/aare/data/jungfrau_single_master_0.json");
-    auto fileHandler = new JFileHandler (fpath);
+    // std::filesystem::path fpath("/home/bb/github/aare/data/jungfrau_single_master_0.json");
+    std::filesystem::path fpath("/home/bb/github/aare/data/test_numpy_file.npy");
+
+    auto fileHandler = new JFileHandler(fpath);
+    test(fileHandler, 0);
+    test(fileHandler, 24);
+
     delete fileHandler;
+
 }
diff --git a/file_io/include/aare/File.hpp b/file_io/include/aare/File.hpp
index 0a4f628..75c4d28 100644
--- a/file_io/include/aare/File.hpp
+++ b/file_io/include/aare/File.hpp
@@ -15,6 +15,8 @@ class File {
     virtual Frame<DataType>* get_frame(int frame_number) = 0;
 
   private:
+  //comment
+  
 
   public:
     std::filesystem::path fname;
diff --git a/file_io/include/aare/JsonFileFactory.hpp b/file_io/include/aare/JsonFileFactory.hpp
index a65453c..4c0ffac 100644
--- a/file_io/include/aare/JsonFileFactory.hpp
+++ b/file_io/include/aare/JsonFileFactory.hpp
@@ -5,11 +5,10 @@ class JsonFileFactory: public FileFactory<detector,DataType>
 private:
     /* data */
 public:
+    JsonFileFactory(std::filesystem::path fpath);
     File<detector,DataType>* load_file() override;
     void parse_metadata(File<detector,DataType>*) override;
     void parse_fname(File<detector,DataType>*) override;
-
-    JsonFileFactory<detector,DataType>(std::filesystem::path fpath);
     void open_subfiles(File<detector,DataType>*);
     sls_detector_header read_header(const std::filesystem::path &fname);
     void find_geometry(File<detector,DataType>*);
diff --git a/file_io/include/aare/NumpyFile.hpp b/file_io/include/aare/NumpyFile.hpp
index 1230af9..33ab769 100644
--- a/file_io/include/aare/NumpyFile.hpp
+++ b/file_io/include/aare/NumpyFile.hpp
@@ -1,9 +1,52 @@
+#pragma once
 #include "aare/File.hpp"
 #include "aare/defs.hpp"
+#include <iostream>
+#include <numeric>
 
-template <DetectorType detector, typename DataType>
-class NumpyFile : public File<detector, DataType>
-{
+using shape_t = std::vector<uint64_t>;
+
+struct dtype_t {
+    char byteorder;
+    char kind;
+    unsigned int itemsize;
+    std::string to_string() {
+        std::stringstream sstm;
+        sstm << byteorder << kind << itemsize;
+        return sstm.str();
+    }
+};
+struct header_t {
+    dtype_t dtype;
+    bool fortran_order;
+    shape_t shape;
+    std::string to_string() {
+        std::stringstream sstm;
+        sstm << "dtype: " << dtype.to_string() << ", fortran_order: " << fortran_order << ' ';
+
+        sstm << "shape: (";
+        for (auto item : shape)
+            sstm << item << ',';
+        sstm << ')';
+        return sstm.str();
+    }
+};
+template <DetectorType detector, typename DataType> class NumpyFile : public File<detector, DataType> {
+    FILE *fp = nullptr;
     
-
+  public:
+    NumpyFile(std::filesystem::path fname);
+    Frame<DataType> *get_frame(int frame_number) override;
+    header_t header{};
+    static constexpr std::array<char, 6> magic_str{'\x93', 'N', 'U', 'M', 'P', 'Y'};
+    uint8_t major_ver_{};
+    uint8_t minor_ver_{};
+    uint32_t header_len{};
+    uint8_t header_len_size{};
+    const uint8_t magic_string_length{6};
+    ssize_t header_size{};
+    inline ssize_t pixels_per_frame() {
+        return std::accumulate(header.shape.begin() + 1, header.shape.end(), 1, std::multiplies<uint64_t>());
+    };
+    inline ssize_t bytes_per_frame() { return header.dtype.itemsize * pixels_per_frame(); };
 };
\ No newline at end of file
diff --git a/file_io/include/aare/NumpyFileFactory.hpp b/file_io/include/aare/NumpyFileFactory.hpp
index 3ba3903..f75fcf6 100644
--- a/file_io/include/aare/NumpyFileFactory.hpp
+++ b/file_io/include/aare/NumpyFileFactory.hpp
@@ -1,6 +1,7 @@
-#include "aare/defs.hpp"
+#pragma once
 #include "aare/FileFactory.hpp"
 #include "aare/NumpyFile.hpp"
+#include "aare/defs.hpp"
 #include <algorithm>
 #include <array>
 #include <filesystem>
@@ -8,22 +9,17 @@
 #include <string>
 #include <unordered_map>
 #include <vector>
+#include <sstream>
 
 template <DetectorType detector, typename DataType> class NumpyFileFactory : public FileFactory<detector, DataType> {
+  private:
+    std::ifstream f;
+    void read_data(File<detector, DataType> *_file);
+
   public:
     NumpyFileFactory(std::filesystem::path fpath);
     void parse_metadata(File<detector, DataType> *_file) override;
-    void open_subfiles(File<detector, DataType> *_file) override;
     File<detector, DataType> *load_file() override;
+    void parse_fname(File<detector, DataType> *){};
 
-    uint8_t major_ver() const noexcept { return major_ver_; }
-    uint8_t minor_ver() const noexcept { return minor_ver_; }
-
-  private:
-    static constexpr std::array<char, 6> magic_str{'\x93', 'N', 'U', 'M', 'P', 'Y'};
-    uint8_t major_ver_{};
-    uint8_t minor_ver_{};
-    uint32_t header_len{};
-    uint8_t header_len_size{};
-    const uint8_t magic_string_length{6};
 };
\ No newline at end of file
diff --git a/file_io/src/FileFactory.cpp b/file_io/src/FileFactory.cpp
index 9e7ed47..37eaf0c 100644
--- a/file_io/src/FileFactory.cpp
+++ b/file_io/src/FileFactory.cpp
@@ -1,6 +1,7 @@
 #include "aare/FileFactory.hpp"
 #include "aare/File.hpp"
 #include "aare/JsonFileFactory.hpp"
+#include "aare/NumpyFileFactory.hpp"
 #include <iostream>
 
 template <DetectorType detector, typename DataType>
@@ -20,7 +21,7 @@ FileFactory<detector, DataType> *FileFactory<detector, DataType>::get_factory(st
     // check if extension is numpy
     else if (fpath.extension() == ".npy") {
         std::cout << "Loading numpy file" << std::endl;
-        throw std::runtime_error("Numpy file not implemented");
+        return new NumpyFileFactory<detector, DataType>(fpath);
     }
 
     throw std::runtime_error("Unsupported file type");
diff --git a/file_io/src/JsonFile.cpp b/file_io/src/JsonFile.cpp
index c900e74..503b6fa 100644
--- a/file_io/src/JsonFile.cpp
+++ b/file_io/src/JsonFile.cpp
@@ -2,6 +2,9 @@
 
 template <DetectorType detector, typename DataType>
 Frame<DataType> *JsonFile<detector, DataType>::get_frame(int frame_number) {
+    if (frame_number > this->total_frames) {
+        throw std::runtime_error("Frame number out of range");
+    }
     int subfile_id = frame_number / this->max_frames_per_file;
     std::byte *buffer;
     size_t frame_size = this->subfiles[subfile_id]->bytes_per_frame();
diff --git a/file_io/src/NumpyFile.cpp b/file_io/src/NumpyFile.cpp
index e69de29..78de3d8 100644
--- a/file_io/src/NumpyFile.cpp
+++ b/file_io/src/NumpyFile.cpp
@@ -0,0 +1,24 @@
+
+#include "aare/NumpyFile.hpp"
+
+template <DetectorType detector, typename DataType>
+NumpyFile<detector, DataType>::NumpyFile(std::filesystem::path fname){
+    this->fname = fname;
+    fp = fopen(fname.c_str(), "rb");
+}
+
+template <DetectorType detector, typename DataType>
+Frame<DataType> *NumpyFile<detector, DataType>::get_frame(int frame_number) {
+    if (fp == nullptr) {
+        throw std::runtime_error("File not open");
+    }
+    if (frame_number > header.shape[0]) {
+        throw std::runtime_error("Frame number out of range");
+    }
+    Frame<DataType> *frame = new Frame<DataType>(header.shape[1], header.shape[2]);
+    fseek(fp, header_size + frame_number * bytes_per_frame(), SEEK_SET);
+    fread(frame->data, sizeof(DataType), pixels_per_frame(), fp);
+    return frame;
+}
+
+template class NumpyFile<DetectorType::Jungfrau, uint16_t>;
\ No newline at end of file
diff --git a/file_io/src/NumpyFileFactory.cpp b/file_io/src/NumpyFileFactory.cpp
index fc5d470..fd15970 100644
--- a/file_io/src/NumpyFileFactory.cpp
+++ b/file_io/src/NumpyFileFactory.cpp
@@ -13,8 +13,8 @@ inline std::string parse_str(const std::string &in) {
 /**
   Removes leading and trailing whitespaces
   */
-inline std::string trim(const std::string& str) {
-    const std::string whitespace = " \t";
+inline std::string trim(const std::string &str) {
+    const std::string whitespace = " \t\n";
     auto begin = str.find_first_not_of(whitespace);
 
     if (begin == std::string::npos)
@@ -52,7 +52,6 @@ inline bool parse_bool(const std::string &in) {
     throw std::runtime_error("Invalid python boolan.");
 }
 
-
 inline std::string get_value_from_map(const std::string &mapstr) {
     size_t sep_pos = mapstr.find_first_of(":");
     if (sep_pos == std::string::npos)
@@ -63,7 +62,6 @@ inline std::string get_value_from_map(const std::string &mapstr) {
 }
 std::unordered_map<std::string, std::string> parse_dict(std::string in, const std::vector<std::string> &keys) {
     std::unordered_map<std::string, std::string> map;
-
     if (keys.size() == 0)
         return map;
 
@@ -113,19 +111,6 @@ std::unordered_map<std::string, std::string> parse_dict(std::string in, const st
     return map;
 }
 
-
-using shape_t = std::vector<uint64_t>;
-
-struct dtype_t {
-    char byteorder;
-    char kind;
-    unsigned int itemsize;
-};
-struct header_t {
-    dtype_t dtype;
-    bool fortran_order;
-    shape_t shape;
-};
 template <typename T, size_t N> inline bool in_array(T val, const std::array<T, N> &arr) {
     return std::find(std::begin(arr), std::end(arr), val) != std::end(arr);
 }
@@ -160,14 +145,15 @@ template <DetectorType detector, typename DataType>
 void NumpyFileFactory<detector, DataType>::parse_metadata(File<detector, DataType> *_file) {
     auto file = dynamic_cast<NumpyFile<detector, DataType> *>(_file);
     // open ifsteam to file
-    std::ifstream f(file->fname, std::ios::binary);
+    f = std::ifstream(file->fname, std::ios::binary);
+    // check if file exists
     if (!f.is_open()) {
         throw std::runtime_error(fmt::format("Could not open: {} for reading", file->fname.c_str()));
     }
     // read magic number
     std::array<char, 6> tmp{};
     f.read(tmp.data(), tmp.size());
-    if (tmp != NumpyFileFactory<detector, DataType>::magic_str) {
+    if (tmp != NumpyFile<detector, DataType>::magic_str) {
         for (auto item : tmp)
             fmt::print("{}, ", int(item));
         fmt::print("\n");
@@ -175,29 +161,31 @@ void NumpyFileFactory<detector, DataType>::parse_metadata(File<detector, DataTyp
     }
 
     // read version
-    f.read(reinterpret_cast<char *>(&major_ver_), 1);
-    f.read(reinterpret_cast<char *>(&minor_ver_), 1);
+    f.read(reinterpret_cast<char *>(&file->major_ver_), 1);
+    f.read(reinterpret_cast<char *>(&file->minor_ver_), 1);
 
-    if (major_ver_ == 1) {
-        header_len_size = 2;
-    } else if (major_ver_ == 2) {
-        header_len_size = 4;
+    if (file->major_ver_ == 1) {
+        file->header_len_size = 2;
+    } else if (file->major_ver_ == 2) {
+        file->header_len_size = 4;
     } else {
         throw std::runtime_error("Unsupported numpy version");
     }
     // read header length
-    f.read(reinterpret_cast<char *>(&header_len), header_len_size);
-    if ((magic_string_length + 2 + header_len_size + header_len) % 16 != 0) {
+    f.read(reinterpret_cast<char *>(&file->header_len), file->header_len_size);
+    file->header_size = file->magic_string_length + 2 + file->header_len_size + file->header_len;
+    if (file->header_size % 16 != 0) {
         fmt::print("Warning: header length is not a multiple of 16\n");
     }
     // read header
-    auto buf_v = std::vector<char>(header_len);
-    f.read(buf_v.data(), header_len);
-    std::string header(buf_v.data(), header_len);
+    auto buf_v = std::vector<char>(file->header_len);
+    f.read(buf_v.data(), file->header_len);
+    std::string header(buf_v.data(), file->header_len);
 
     // parse header
 
     std::vector<std::string> keys{"descr", "fortran_order", "shape"};
+    std::cout << "original header: " << '"' << header << '"' << std::endl;
 
     auto dict_map = parse_dict(header, keys);
     if (dict_map.size() == 0)
@@ -220,6 +208,23 @@ void NumpyFileFactory<detector, DataType>::parse_metadata(File<detector, DataTyp
         auto dim = static_cast<unsigned long>(std::stoul(item));
         shape.push_back(dim);
     }
+    file->header = {dtype, fortran_order, shape};
+}
+
+template <DetectorType detector, typename DataType>
+ File<detector, DataType>* NumpyFileFactory<detector, DataType>::load_file() {
+    NumpyFile<detector, DataType> *file = new NumpyFile<detector, DataType>(this->fpath);
+    parse_metadata(file);
+    NumpyFile<detector, DataType> *f = dynamic_cast<NumpyFile<detector, DataType> *>(file);
+    std::cout << "parsed header: " << f->header.to_string() << std::endl;
+
+    if(sizeof(DataType) != f->header.dtype.itemsize){
+        std::stringstream  s;
+        s << "Data type size mismatch: " << sizeof(DataType) << " != " << f->header.dtype.itemsize;
+        throw std::runtime_error(s.str());
+    }       
+    return file;
+};
+template class NumpyFileFactory<DetectorType::Jungfrau, uint16_t>;
+
 
-    // {dtype, fortran_order, shape};
-};
\ No newline at end of file