Demo code: add in-memory png image encoding and data saving into npy/…

…npz file format.

modules/core/include/visp3/core/vpIoTools.h

@@ -47,6 +47,8 @@
 #include <stdlib.h>
 #include <string>
 #include <vector>
+#include <numeric>
+#include <zlib.h>
 #include <visp3/core/vpColor.h>
 
 /*!
@@ -150,6 +152,294 @@ int main()
 
  */
 
+// TODO:
+// Copyright (C) 2011  Carl Rogers
+// Released under MIT License
+// license available in LICENSE file, or at http://www.opensource.org/licenses/mit-license.php
+
+// reference: https://stackoverflow.com/a/2164853
+#if defined(_MSC_VER)
+    //  Microsoft
+#define EXPORT __declspec(dllexport)
+#define IMPORT __declspec(dllimport)
+#elif defined(__GNUC__)
+    //  GCC
+#define EXPORT __attribute__((visibility("default")))
+#define IMPORT
+#else
+    //  do nothing and hope for the best?
+#define EXPORT
+#define IMPORT
+#pragma warning Unknown dynamic link import/export semantics.
+#endif
+
+
+#if defined(VISP_HAVE_CXX11)
+
+#include <memory>
+#include <map>
+#include <cassert>
+#include <complex>
+
+namespace visp
+{
+namespace cnpy
+{
+struct NpyArray
+{
+  NpyArray(const std::vector<size_t> &_shape, size_t _word_size, bool _fortran_order) :
+    shape(_shape), word_size(_word_size), fortran_order(_fortran_order)
+  {
+    num_vals = 1;
+    for (size_t i = 0;i < shape.size();i++) num_vals *= shape[i];
+    data_holder = std::shared_ptr<std::vector<char>>(
+        new std::vector<char>(num_vals * word_size));
+  }
+
+  NpyArray() : shape(0), word_size(0), fortran_order(0), num_vals(0) { }
+
+  template<typename T>
+  T *data()
+  {
+    return reinterpret_cast<T *>(&(*data_holder)[0]);
+  }
+
+  template<typename T>
+  const T *data() const
+  {
+    return reinterpret_cast<T *>(&(*data_holder)[0]);
+  }
+
+  template<typename T>
+  std::vector<T> as_vec() const
+  {
+    const T *p = data<T>();
+    return std::vector<T>(p, p+num_vals);
+  }
+
+  size_t num_bytes() const
+  {
+    return data_holder->size();
+  }
+
+  std::shared_ptr<std::vector<char>> data_holder;
+  std::vector<size_t> shape;
+  size_t word_size;
+  bool fortran_order;
+  size_t num_vals;
+};
+
+using npz_t = std::map<std::string, NpyArray>;
+
+EXPORT char BigEndianTest();
+EXPORT char map_type(const std::type_info &t);
+template<typename T> EXPORT std::vector<char> create_npy_header(const std::vector<size_t> &shape);
+EXPORT void parse_npy_header(FILE *fp, size_t &word_size, std::vector<size_t> &shape, bool &fortran_order);
+EXPORT void parse_npy_header(unsigned char *buffer, size_t &word_size, std::vector<size_t> &shape, bool &fortran_order);
+EXPORT void parse_zip_footer(FILE *fp, uint16_t &nrecs, size_t &global_header_size, size_t &global_header_offset);
+EXPORT npz_t npz_load(std::string fname);
+EXPORT NpyArray npz_load(std::string fname, std::string varname);
+EXPORT NpyArray npy_load(std::string fname);
+
+template<typename T> EXPORT std::vector<char> &operator+=(std::vector<char> &lhs, const T rhs)
+{
+//write in little endian
+  for (size_t byte = 0; byte < sizeof(T); byte++) {
+    char val = *((char *)&rhs+byte);
+    lhs.push_back(val);
+  }
+  return lhs;
+}
+
+template<> EXPORT std::vector<char> &operator+=(std::vector<char> &lhs, const std::string rhs);
+template<> EXPORT std::vector<char> &operator+=(std::vector<char> &lhs, const char *rhs);
+
+
+template<typename T> EXPORT void npy_save(std::string fname, const T *data, const std::vector<size_t> shape, std::string mode = "w")
+{
+  FILE *fp = NULL;
+  std::vector<size_t> true_data_shape; //if appending, the shape of existing + new data
+
+  if (mode == "a") fp = fopen(fname.c_str(), "r+b");
+
+  if (fp) {
+      //file exists. we need to append to it. read the header, modify the array size
+    size_t word_size;
+    bool fortran_order;
+    parse_npy_header(fp, word_size, true_data_shape, fortran_order);
+    assert(!fortran_order);
+
+    if (word_size != sizeof(T)) {
+      std::cout<<"libnpy error: "<<fname<<" has word size "<<word_size<<" but npy_save appending data sized "<<sizeof(T)<<"\n";
+      assert(word_size == sizeof(T));
+    }
+    if (true_data_shape.size() != shape.size()) {
+      std::cout<<"libnpy error: npy_save attempting to append misdimensioned data to "<<fname<<"\n";
+      assert(true_data_shape.size() != shape.size());
+    }
+
+    for (size_t i = 1; i < shape.size(); i++) {
+      if (shape[i] != true_data_shape[i]) {
+        std::cout<<"libnpy error: npy_save attempting to append misshaped data to "<<fname<<"\n";
+        assert(shape[i] == true_data_shape[i]);
+      }
+    }
+    true_data_shape[0] += shape[0];
+  }
+  else {
+    fp = fopen(fname.c_str(), "wb");
+    true_data_shape = shape;
+  }
+
+  std::vector<char> header = create_npy_header<T>(true_data_shape);
+  size_t nels = std::accumulate(shape.begin(), shape.end(), 1, std::multiplies<size_t>());
+
+  fseek(fp, 0, SEEK_SET);
+  fwrite(&header[0], sizeof(char), header.size(), fp);
+  fseek(fp, 0, SEEK_END);
+  fwrite(data, sizeof(T), nels, fp);
+  fclose(fp);
+}
+
+template<typename T> EXPORT void npz_save(std::string zipname, std::string fname, const T *data, const std::vector<size_t> &shape, std::string mode = "w")
+{
+    //first, append a .npy to the fname
+  fname += ".npy";
+
+  //now, on with the show
+  FILE *fp = NULL;
+  uint16_t nrecs = 0;
+  size_t global_header_offset = 0;
+  std::vector<char> global_header;
+
+  if (mode == "a") fp = fopen(zipname.c_str(), "r+b");
+
+  if (fp) {
+      //zip file exists. we need to add a new npy file to it.
+      //first read the footer. this gives us the offset and size of the global header
+      //then read and store the global header.
+      //below, we will write the the new data at the start of the global header then append the global header and footer below it
+    size_t global_header_size;
+    parse_zip_footer(fp, nrecs, global_header_size, global_header_offset);
+    fseek(fp, global_header_offset, SEEK_SET);
+    global_header.resize(global_header_size);
+    size_t res = fread(&global_header[0], sizeof(char), global_header_size, fp);
+    if (res != global_header_size) {
+      throw std::runtime_error("npz_save: header read error while adding to existing zip");
+    }
+    fseek(fp, global_header_offset, SEEK_SET);
+  }
+  else {
+    fp = fopen(zipname.c_str(), "wb");
+  }
+
+  std::vector<char> npy_header = create_npy_header<T>(shape);
+
+  size_t nels = std::accumulate(shape.begin(), shape.end(), 1, std::multiplies<size_t>());
+  size_t nbytes = nels*sizeof(T) + npy_header.size();
+
+  //get the CRC of the data to be added
+  uint32_t crc = crc32(0L, (uint8_t *)&npy_header[0], npy_header.size());
+  crc = crc32(crc, (uint8_t *)data, nels*sizeof(T));
+
+  //build the local header
+  std::vector<char> local_header;
+  local_header += "PK"; //first part of sig
+  local_header += (uint16_t)0x0403; //second part of sig
+  local_header += (uint16_t)20; //min version to extract
+  local_header += (uint16_t)0; //general purpose bit flag
+  local_header += (uint16_t)0; //compression method
+  local_header += (uint16_t)0; //file last mod time
+  local_header += (uint16_t)0;     //file last mod date
+  local_header += (uint32_t)crc; //crc
+  local_header += (uint32_t)nbytes; //compressed size
+  local_header += (uint32_t)nbytes; //uncompressed size
+  local_header += (uint16_t)fname.size(); //fname length
+  local_header += (uint16_t)0; //extra field length
+  local_header += fname;
+
+  //build global header
+  global_header += "PK"; //first part of sig
+  global_header += (uint16_t)0x0201; //second part of sig
+  global_header += (uint16_t)20; //version made by
+  global_header.insert(global_header.end(), local_header.begin()+4, local_header.begin()+30);
+  global_header += (uint16_t)0; //file comment length
+  global_header += (uint16_t)0; //disk number where file starts
+  global_header += (uint16_t)0; //internal file attributes
+  global_header += (uint32_t)0; //external file attributes
+  global_header += (uint32_t)global_header_offset; //relative offset of local file header, since it begins where the global header used to begin
+  global_header += fname;
+
+  //build footer
+  std::vector<char> footer;
+  footer += "PK"; //first part of sig
+  footer += (uint16_t)0x0605; //second part of sig
+  footer += (uint16_t)0; //number of this disk
+  footer += (uint16_t)0; //disk where footer starts
+  footer += (uint16_t)(nrecs+1); //number of records on this disk
+  footer += (uint16_t)(nrecs+1); //total number of records
+  footer += (uint32_t)global_header.size(); //nbytes of global headers
+  footer += (uint32_t)(global_header_offset + nbytes + local_header.size()); //offset of start of global headers, since global header now starts after newly written array
+  footer += (uint16_t)0; //zip file comment length
+
+  //write everything
+  fwrite(&local_header[0], sizeof(char), local_header.size(), fp);
+  fwrite(&npy_header[0], sizeof(char), npy_header.size(), fp);
+  fwrite(data, sizeof(T), nels, fp);
+  fwrite(&global_header[0], sizeof(char), global_header.size(), fp);
+  fwrite(&footer[0], sizeof(char), footer.size(), fp);
+  fclose(fp);
+}
+
+template<typename T> EXPORT void npy_save(std::string fname, const std::vector<T> data, std::string mode = "w")
+{
+  std::vector<size_t> shape;
+  shape.push_back(data.size());
+  npy_save(fname, &data[0], shape, mode);
+}
+
+template<typename T> EXPORT void npz_save(std::string zipname, std::string fname, const std::vector<T> data, std::string mode = "w")
+{
+  std::vector<size_t> shape;
+  shape.push_back(data.size());
+  npz_save(zipname, fname, &data[0], shape, mode);
+}
+
+template<typename T> EXPORT std::vector<char> create_npy_header(const std::vector<size_t> &shape)
+{
+  std::vector<char> dict;
+  dict += "{'descr': '";
+  dict += BigEndianTest();
+  dict += map_type(typeid(T));
+  dict += std::to_string(sizeof(T));
+  dict += "', 'fortran_order': False, 'shape': (";
+  dict += std::to_string(shape[0]);
+  for (size_t i = 1;i < shape.size();i++) {
+    dict += ", ";
+    dict += std::to_string(shape[i]);
+  }
+  if (shape.size() == 1) dict += ",";
+  dict += "), }";
+  //pad with spaces so that preamble+dict is modulo 16 bytes. preamble is 10 bytes. dict needs to end with \n
+  int remainder = 16 - (10 + dict.size()) % 16;
+  dict.insert(dict.end(), remainder, ' ');
+  dict.back() = '\n';
+
+  std::vector<char> header;
+  header += (char)0x93;
+  header += "NUMPY";
+  header += (char)0x01; //major version of numpy format
+  header += (char)0x00; //minor version of numpy format
+  header += (uint16_t)dict.size();
+  header.insert(header.end(), dict.begin(), dict.end());
+
+  return header;
+}
+
+}
+}
+#endif
+
 class VISP_EXPORT vpIoTools
 {