Feature: Read EXR files from memory

testing/data/DATA_LICENSES.md

@@ -57,6 +57,8 @@
 - world*: VTK Data: BSD-3-Clause
 - 16bits.*: @bisechen: [CC0](https://creativecommons.org/publicdomain/zero/1.0/)
 - (ノಠ益ಠ )ノ.vtp: VTK Data: BSD-3-Clause
+- Rec709.exr: [Copyright 2006 Industrial Light & Magic](https://github.com/AcademySoftwareFoundation/openexr/blob/370db2835843ac75f85e1386c05455f26a6ff58c/website/test_images/Chromaticities/Rec709.rst): BSD-3-Clause
+- small.usdz: [Copyright USD contributors](https://github.com/usd-wg/assets/tree/main/full_assets/StandardShaderBall): [CC-BY 4.0](https://creativecommons.org/licenses/by/4.0/)
 
 All other datasets are licensed under the BSD-3-Clause F3D license.
 

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()
 
 vtk_add_test_cxx(vtkextPrivateTests tests

vtkext/private/module/Testing/TestF3DEXRMemReader.cxx

@@ -0,0 +1,50 @@
+#include <vtkImageData.h>
+#include <vtkNew.h>
+
+#include "vtkF3DEXRReader.h"
+
+#include <fstream>
+#include <iostream>
+#include <vector>
+
+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);
+  return file.read(buffer.data(), size) ? true : 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 +8,60 @@
 #include "vtksys/FStream.hxx"
 
 #include <ImfArray.h>
+#include <ImfIO.h>
 #include <ImfRgbaFile.h>
 
+#include <algorithm>
 #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))
+  {
+  }
+
+  bool read(char c[], int n) override
+  {
+    if (pos + n <= bufflen)
+    {
+      std::copy_n(buffer + pos, n, c);
+      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{ 0 };
+};
+
 vtkStandardNewMacro(vtkF3DEXRReader);
 
 //------------------------------------------------------------------------------
@@ -36,15 +85,14 @@ void vtkF3DEXRReader::ExecuteInformation()
 
   // Setup filename to read the header
   this->ComputeInternalFileName(this->DataExtent[4]);
-  if (this->InternalFileName == nullptr || this->InternalFileName[0] == '\0')
+  if ((this->InternalFileName == nullptr || this->InternalFileName[0] == '\0') &&
+    !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 +104,21 @@ void vtkF3DEXRReader::ExecuteInformation()
     {
       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 +175,8 @@ void vtkF3DEXRReader::ExecuteDataWithInformation(vtkDataObject* output, vtkInfor
   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 +193,23 @@ void vtkF3DEXRReader::ExecuteDataWithInformation(vtkDataObject* output, vtkInfor
         dataPtr += 3;
       }
     }
+  };
+
+  try
+  {
+    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)
   {