Method ExecuteInformation

IO/Image/vtkPNGReader.cxx:287–429

------------------------------------------------------------------------------

//------------------------------------------------------------------------------
void vtkPNGReader::ExecuteInformation()
{
  vtkInternals* impl = this->Internals;
  FILE* fp = nullptr;
  MemoryBufferStream stream;

  if (this->GetStream())
  {
    // Reset stream to the beginning
    this->GetStream()->Seek(0, vtkResourceStream::SeekDirection::Begin);

    // Read the header from MemoryBuffer
    if (!impl->CheckBufferHeaderStream(this->GetStream()))
    {
      vtkErrorMacro("Invalid MemoryBuffer header: not a PNG file");
      this->SetErrorCode(vtkErrorCode::UnrecognizedFileTypeError);
      return;
    }
  }
  else if (this->GetMemoryBuffer())
  {
    // VTK_DEPRECATED_IN_9_6_0
    // Read the header from MemoryBuffer
    const unsigned char* memBuffer = static_cast<const unsigned char*>(this->GetMemoryBuffer());
    if (!impl->CheckBufferHeader(memBuffer, this->GetMemoryBufferLength()))
    {
      vtkErrorMacro("Invalid MemoryBuffer header: not a PNG file");
      this->SetErrorCode(vtkErrorCode::UnrecognizedFileTypeError);
      return;
    }
  }
  else
  {
    // Attempt to open the file and read the header
    this->ComputeInternalFileName(this->DataExtent[4]);
    if (this->InternalFileName == nullptr)
    {
      vtkErrorMacro("A filename must be specified");
      this->SetErrorCode(vtkErrorCode::NoFileNameError);
      return;
    }
    fp = vtksys::SystemTools::Fopen(this->InternalFileName, "rb");
    if (!fp)
    {
      vtkErrorMacro("Unable to open file " << this->InternalFileName);
      this->SetErrorCode(vtkErrorCode::CannotOpenFileError);
      return;
    }
    if (!impl->CheckFileHeader(fp))
    {
      vtkErrorMacro("Invalid file header: not a PNG file");
      fclose(fp);
      this->SetErrorCode(vtkErrorCode::FileFormatError);
      return;
    }
  }

  png_structp png_ptr = nullptr;