message: compute diff image in example
diff: @@ -231,13 +231,14 @@ int main(int argc, char* argv[])
  {
  // Verify the output values
  std::cout << "Verifying output" << std::endl;
  +
  + ImageBuffer diff(width, height, 3);
  int nerr = 0;
  float maxre = 0;
  +
  for (size_t i = 0; i < output.getDataSize(); ++i)
  {
  float expect = std::max(ref[i], 0.f);
  - if (!hdr)
  - expect = std::min(expect, 1.f);
  const float actual = output[i];
  float re;
  if (std::abs(expect) < 1e-5 && std::abs(actual) < 1e-5)
  @@ -252,6 +253,8 @@ int main(int argc, char* argv[])
  //std::cout << "i=" << i << " expect=" << expect << " actual=" << actual << std::endl;
  ++nerr;
  }
  +
  + diff[i] = std::abs(ref[i] - output[i]);
  }
  std::cout << " nfloats=" << output.getDataSize() << ", nerr=" << nerr << ", maxre=" << maxre << std::endl;
  @@ -260,6 +263,7 @@ int main(int argc, char* argv[])
  saveImage("denoise_in.ppm", color);
  saveImage("denoise_out.ppm", output);
  saveImage("denoise_ref.ppm", ref);
  + saveImage("denoise_diff.ppm", diff);
  }
  if (!outputFilename.empty())
  