Feature/1187 Read EXR files from memory

application/testing/CMakeLists.txt

@@ -677,6 +677,9 @@ if(F3D_PLUGIN_BUILD_USD)
 
   # https://gitlab.kitware.com/vtk/vtk/-/merge_requests/8224
   if(VTK_VERSION VERSION_GREATER_EQUAL 9.0.20210805) # for embedded material support
+    if(F3D_MODULE_EXR)
+      f3d_test(NAME TestEXRReadMemory DATA sphere8.usdz ARGS --load-plugins=usd DEFAULT_LIGHTS)
+    endif()
     f3d_test(NAME TestUSDZAnimated DATA AnimatedCube.usdz ARGS --load-plugins=usd --animation-time=0.3)
     f3d_test(NAME TestUSDZRigged DATA RiggedSimple.usdz ARGS --load-plugins=usd --animation-time=0.3)
 

vtkext/private/module/Testing/CMakeLists.txt

@@ -17,7 +17,8 @@ endif()
 if(F3D_MODULE_EXR)
   list(APPEND test_sources 
        TestF3DEXRReader.cxx
-       TestF3DEXRReaderInvalid.cxx)
+       TestF3DEXRReaderInvalid.cxx
+       TestF3DEXRMemReader.cxx)
 endif()
 
 if(VTK_VERSION VERSION_LESS_EQUAL 9.1.0)

vtkext/private/module/Testing/TestF3DEXRMemReader.cxx

@@ -0,0 +1,57 @@
+#include <vtkImageData.h>
+#include <vtkNew.h>
+
+#include "vtkF3DEXRReader.h"
+
+#include <fstream>
+#include <iostream>
+#include <vector>
+/**
+ * image file taken from
+ * https://github.com/AcademySoftwareFoundation/openexr/blob/370db2835843ac75f85e1386c05455f26a6ff58c/website/test_images/Chromaticities/Rec709.rst
+ */
+bool readFileToVector(const std::string& filename, std::vector<char>& buffer)
+{
+  std::ifstream file(filename, std::ios::binary | std::ios::ate);
+  if (!file)
+  {
+    return false;
+  }
+
+  std::streamsize size = file.tellg();
+  file.seekg(0, std::ios::beg);
+
+  buffer.resize(size);
+
+  if (file.read(buffer.data(), size))
+    return true;
+  return false;
+}
+
+int TestF3DEXRMemReader(int argc, char* argv[])
+{
+  vtkNew<vtkF3DEXRReader> reader;
+
+  std::string actual_filename = std::string(argv[1]) + "data/Rec709.exr";
+  std::string filename = "readFromMem.exr";
+  reader->SetFileName(filename.c_str());
+  std::vector<char> buff;
+  readFileToVector(actual_filename, buff);
+  reader->SetMemoryBuffer(buff.data());
+  reader->SetMemoryBufferLength(buff.size());
+  reader->Update();
+
+  reader->Print(cout);
+
+  vtkImageData* img = reader->GetOutput();
+
+  int* dims = img->GetDimensions();
+
+  if (dims[0] != 610 && dims[1] != 406)
+  {
+    std::cerr << "Incorrect EXR image size." << dims[0] << ":" << dims[1] << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
+}

vtkext/private/module/vtkF3DEXRReader.cxx

@@ -8,11 +8,61 @@
 #include "vtksys/FStream.hxx"
 
 #include <ImfArray.h>
+#include <ImfIO.h>
 #include <ImfRgbaFile.h>
 
+#include <cstring>
 #include <sstream>
 #include <thread>
 
+/**
+ * Class to treat file contents in memory like it were still in a file.
+ */
+class MemStream : public Imf::IStream
+{
+public:
+  MemStream(const char* name, const void* buff, vtkIdType bufferLen)
+    : Imf::IStream(name)
+    , buffer(static_cast<const char*>(buff))
+    , bufflen(static_cast<size_t>(bufferLen))
+    , pos(0)
+  {
+  }
+
+  bool read(char c[], int n) override
+  {
+    if (pos + n <= bufflen)
+    {
+      memcpy(c, buffer + pos, n);
+      pos += n;
+      return true;
+    }
+    return false;
+  }
+
+  /**
+   * returns the current reading position, in bytes, from the beginning of the file.
+   * The next read() call will begin reading at the indicated position
+   */
+  uint64_t tellg() override
+  {
+    return pos;
+  }
+
+  /**
+   * sets the current reading position to pos bytes from the beginning of the "file"
+   */
+  void seekg(uint64_t new_pos) override
+  {
+    pos = new_pos;
+  }
+
+private:
+  const char* buffer;
+  size_t bufflen;
+  uint64_t pos;
+};
+
 vtkStandardNewMacro(vtkF3DEXRReader);
 
 //------------------------------------------------------------------------------
@@ -38,13 +88,13 @@
   this->ComputeInternalFileName(this->DataExtent[4]);
   if (this->InternalFileName == nullptr || this->InternalFileName[0] == '\0')
   {
-    return;
+    // If we have no file then maybe we have the file in memory
+    if (!this->MemoryBuffer)
+      return;
   }
 
-  try
+  auto execute = [&](Imf::RgbaInputFile& file)
   {
-    Imf::RgbaInputFile file(this->InternalFileName);
-
     Imath::Box2i dw = file.dataWindow();
     this->DataExtent[0] = dw.min.x;
     this->DataExtent[1] = dw.max.x;
@@ -56,6 +106,21 @@
     {
       throw std::runtime_error("only RGB and RGBA channels are supported");
     }
+  };
+
+  try
+  {
+    if (this->MemoryBuffer)
+    {
+      MemStream memoryStream("EXRmemoryStream", this->MemoryBuffer, this->MemoryBufferLength);
+      Imf::RgbaInputFile file = Imf::RgbaInputFile(memoryStream);
+      execute(file);
+    }
+    else
+    {
+      Imf::RgbaInputFile file(this->InternalFileName);
+      execute(file);
+    }
   }
   catch (const std::exception& e)
   {
@@ -112,12 +177,8 @@
   scalars->SetName("Pixels");
   float* dataPtr = scalars->GetPointer(0);
 
-  try
+  auto execute = [&](Imf::RgbaInputFile& file)
   {
-    assert(this->InternalFileName);
-    Imf::setGlobalThreadCount(std::thread::hardware_concurrency());
-    Imf::RgbaInputFile file(this->InternalFileName);
-
     Imf::Array2D<Imf::Rgba> pixels(this->GetHeight(), this->GetWidth());
 
     file.setFrameBuffer(&pixels[0][0], 1, this->GetWidth());
@@ -134,6 +195,24 @@
         dataPtr += 3;
       }
     }
+  };
+
+  try
+  {
+    assert(this->InternalFileName);
+    Imf::setGlobalThreadCount(std::thread::hardware_concurrency());
+
+    if (this->MemoryBuffer)
+    {
+      MemStream memoryStream("EXRmemoryStream", this->MemoryBuffer, this->MemoryBufferLength);
+      Imf::RgbaInputFile file = Imf::RgbaInputFile(memoryStream);
+      execute(file);
+    }
+    else
+    {
+      Imf::RgbaInputFile file(this->InternalFileName);
+      execute(file);
+    }
   }
   catch (const std::exception& e)
   {
@@ -142,6 +221,24 @@
   }
 }
 
+//------------------------------------------------------------------------------
+/**
+ * Read from memory instead of file
+ */
+void vtkF3DEXRReader::SetMemoryBuffer(const void* buff)
+{
+  MemoryBuffer = buff;
+}
+
+//------------------------------------------------------------------------------
+/**
+ * Specify the in memory image buffer length.
+ */
+void vtkF3DEXRReader::SetMemoryBufferLength(vtkIdType bufferLen)
+{
+  MemoryBufferLength = bufferLen;
+}
+
 //------------------------------------------------------------------------------
 int vtkF3DEXRReader::GetWidth() const
 {

vtkext/private/module/vtkF3DEXRReader.h

@@ -31,6 +31,16 @@ class vtkF3DEXRReader : public vtkImageReader
     return "OpenEXR";
   }
 
+  /**
+   * Read from memory instead of file
+   */
+  void SetMemoryBuffer(const void* buff) override;
+
+  /**
+   * Specify the in memory image buffer length.
+   */
+  void SetMemoryBufferLength(vtkIdType buflen) override;
+
 protected:
   vtkF3DEXRReader();
   ~vtkF3DEXRReader() override;