Add OpenCV backend. Test using std::vector instead of raw array.

modules/io/include/visp3/io/vpImageIo.h

@@ -98,7 +98,8 @@ int main()
 class VISP_EXPORT vpImageIo
 {
 private:
-  typedef enum {
+  typedef enum
+  {
     FORMAT_PGM,
     FORMAT_PPM,
     FORMAT_JPEG,
@@ -118,7 +119,8 @@ class VISP_EXPORT vpImageIo
 
 public:
   //! Image IO backend for only jpeg and png formats image loading and saving
-  enum vpImageIoBackendType {
+  enum vpImageIoBackendType
+  {
     IO_DEFAULT_BACKEND,    //!< Default backend
     IO_SYSTEM_LIB_BACKEND, //!< Use system libraries like libpng or libjpeg
     IO_OPENCV_BACKEND,     //!< Use OpenCV
@@ -172,12 +174,18 @@ class VISP_EXPORT vpImageIo
 
   static void writeEXR(const vpImage<float> &I, const std::string &filename, int backend = IO_DEFAULT_BACKEND);
   static void writeEXR(const vpImage<vpRGBf> &I, const std::string &filename, int backend = IO_DEFAULT_BACKEND);
-  
+
   // not working with Java bindings generator
   // static void writePNGtoMem(const vpImage<unsigned char> &I, int &last_pos, char *buffer);
   // error: cannot bind non-const lvalue reference of type ‘int&’ to an rvalue of type ‘jint’ {aka ‘int’}
   // need to disable Java when building the library
-  static void readPNGfromMem(const unsigned char *buffer, int last_pos, vpImage<unsigned char> &I);
-  static void writePNGtoMem(const vpImage<unsigned char> &I, int &last_pos, unsigned char *buffer);
+  // static void readPNGfromMem(const unsigned char *buffer, int last_pos, vpImage<unsigned char> &I,
+  //     int backend = IO_DEFAULT_BACKEND);
+  // static void writePNGtoMem(const vpImage<unsigned char> &I, int &last_pos, unsigned char *buffer,
+  //     int backend = IO_DEFAULT_BACKEND);
+  static void readPNGfromMem(const std::vector<unsigned char> &buffer, vpImage<unsigned char> &I,
+      int backend = IO_DEFAULT_BACKEND);
+  static void writePNGtoMem(const vpImage<unsigned char> &I, std::vector<unsigned char> &buffer,
+      int backend = IO_DEFAULT_BACKEND);
 };
 #endif

modules/io/src/image/private/vpImageIoBackend.h

@@ -85,6 +85,9 @@ void writeOpenCV(const vpImage<vpRGBa> &I, const std::string &filename, int qual
 void writeOpenCV(const vpImage<float> &I, const std::string &filename);
 void writeOpenCV(const vpImage<vpRGBf> &I, const std::string &filename);
 
+void readPNGfromMemOpenCV(const std::vector<unsigned char> &buffer, vpImage<unsigned char> &I);
+void writePNGtoMemOpenCV(const vpImage<unsigned char> &I, std::vector<unsigned char> &buffer);
+
 // Simd lib
 void readSimdlib(vpImage<unsigned char> &I, const std::string &filename);
 void readSimdlib(vpImage<vpRGBa> &I, const std::string &filename);
@@ -109,8 +112,8 @@ void writeJPEGStb(const vpImage<vpRGBa> &I, const std::string &filename, int qua
 void writePNGStb(const vpImage<unsigned char> &I, const std::string &filename);
 void writePNGStb(const vpImage<vpRGBa> &I, const std::string &filename);
 
-void vp_readPNGfromMem(const unsigned char *buffer, int last_pos, vpImage<unsigned char> &I);
-void vp_writePNGtoMem(const vpImage<unsigned char> &I, int &last_pos, unsigned char *buffer);
+void readPNGfromMemStb(const std::vector<unsigned char> &buffer, vpImage<unsigned char> &I);
+void writePNGtoMemStb(const vpImage<unsigned char> &I, std::vector<unsigned char> &buffer);
 
 // TinyEXR lib
 void writeEXRTiny(const vpImage<float> &I, const std::string &filename);

modules/io/src/image/private/vpImageIoOpenCV.cpp

@@ -166,6 +166,20 @@ void readOpenCV(vpImage<vpRGBf> &I, const std::string &filename)
 #endif
 }
 
+/*!
+  Read the content of the image bitmap stored in memory and encoded using the PNG format.
+
+  \param buffer : Grayscale image buffer / 1D vector of unsigned char data.
+  \param I : Output decoded grayscale image.
+*/
+void readPNGfromMemOpenCV(const std::vector<unsigned char> &buffer, vpImage<unsigned char> &I)
+{
+  cv::Mat1b buf(buffer.size(), 1, const_cast<unsigned char *>(buffer.data()));
+  cv::Mat1b img = cv::imdecode(buf, cv::IMREAD_GRAYSCALE);
+  I.resize(img.rows, img.cols);
+  std::copy(img.begin(), img.end(), I.bitmap);
+}
+
 /*!
   Write the content of the image bitmap in the file which name is given by \e
   filename. This function writes a JPEG file.
@@ -218,4 +232,19 @@ void writeOpenCV(const vpImage<vpRGBf> &I, const std::string &filename)
   cv::imwrite(filename.c_str(), Ip);
 }
 
+void writePNGtoMemOpenCV(const vpImage<unsigned char> &I, std::vector<unsigned char> &buffer)
+{
+  cv::Mat1b img(I.getRows(), I.getCols(), I.bitmap);
+  std::vector<unsigned char> buf;
+  bool result = cv::imencode(".png", img, buf);
+
+  if (result) {
+    buffer = buf;
+  }
+  else {
+    std::string message = "Cannot write png to memory";
+    throw(vpImageException(vpImageException::ioError, message));
+  }
+}
+
 #endif

modules/io/src/image/private/vpImageIoStb.cpp

@@ -134,31 +134,39 @@ static void custom_stbi_write_mem(void *context, void *data, int size)
 }
 }
 
-void vp_readPNGfromMem(const unsigned char *buffer, int last_pos, vpImage<unsigned char> &I)
+/*!
+  Read the content of the image bitmap stored in memory and encoded using the PNG format.
+
+  \param buffer : Grayscale image buffer or 1D vector of unsigned char data.
+  \param lastPos : Size of the grayscale image buffer.
+  \param I : Output decoded grayscale image.
+*/
+void readPNGfromMemStb(const std::vector<unsigned char> &buffer, vpImage<unsigned char> &I)
 {
   int x = 0, y = 0, comp = 0;
   const int req_channels = 1;
-  unsigned char *buffer_read = stbi_load_from_memory(buffer, last_pos, &x, &y, &comp, req_channels);
+  unsigned char *buffer_read = stbi_load_from_memory(buffer.data(), buffer.size(), &x, &y, &comp, req_channels);
 
   I = vpImage<unsigned char>(buffer_read, y, x, true);
   delete[] buffer_read;
 }
 
-void vp_writePNGtoMem(const vpImage<unsigned char> &I, int &last_pos, unsigned char *buffer)
+void writePNGtoMemStb(const vpImage<unsigned char> &I, std::vector<unsigned char> &buffer)
 {
   const int height = I.getRows();
   const int width = I.getCols();
   const int channels = 1;
 
   custom_stbi_mem_context context;
   context.last_pos = 0;
-  context.context = (void *)buffer;
+  buffer.resize(I.getHeight() * I.getWidth());
+  context.context = (void *)buffer.data();
 
   const int stride_bytes = 0;
   int result = stbi_write_png_to_func(custom_stbi_write_mem, &context, width, height, channels, I.bitmap, stride_bytes);
 
   if (result) {
-    last_pos = context.last_pos;
+    buffer.resize(context.last_pos);
   }
   else {
     std::string message = "Cannot write png to memory, result: " + std::to_string(result);