title: OpenEXR image loading
body: <p>I've started to load EXR images using OpenEXR. I have to get the RGB pixels using floating point type.</p>
  
  <p>For RGB images, there was no problem on loading, using this code:</p>
  
  <pre><code>ImfInputFile *iFile = ImfOpenInputFile(filename);
          FrameBuffer fb;
          const Header &amp;iHeader = iFile.header();
          bool hasRed = false, hasGreen = false, hasBlue = false;
          bool hasY = false;
          Box2i dw = iHeader.dataWindow();
          int width = dw.max.x-dw.min.x+1;
          int height = dw.max.y-dw.min.y+1;
  
          for (ChannelList::ConstIterator it = iHeader.channels().begin(), ite = iHeader.channels().end(); it != ite; it++) {
              if ((strcmp(it.name(), "R") == 0)) { hasRed = true; }
              if ((strcmp(it.name(), "G") == 0)) { hasGreen = true; }
              if ((strcmp(it.name(), "B") == 0)) { hasBlue = true; }
              if (it.channel().type != HALF) {
                  HDR_LOG("Unable to open EXR file \"%s\" (unsupported data type %s)", filename, it.channel().type);
                  return (IEFileCantOpen);
              }
          }
  
          if ((hasRed == true) || (hasGreen == true) || (hasBlue == true)) {
              fb.insert("R", Slice(
                  Imf::FLOAT, (char*)((char*)image-&gt;data + (sizeof(float) * 0)),
                  sizeof(float) * 3,
                  sizeof(float) * width * 3,
                  1, 1,
                  0.0
                  )
              );
              fb.insert("G", Slice(
                  Imf::FLOAT, (char*)((char*)image-&gt;data + (sizeof(float) * 1)),
                  sizeof(float) * 3,
                  sizeof(float) * width * 3,
                  1, 1,
                  0.0
                  )
              );
  
              fb.insert("B", Slice(
                  Imf::FLOAT, (char*)((char*)image-&gt;data + (sizeof(float) * 2)),
                  sizeof(float) * 3,
                  sizeof(float) * width * 3,
                  1, 1,
                  0.0
                  )
              );
  
              iFile.setFrameBuffer(fb);
  
              if (ReadImage(filename, iFile, dw.min.y, dw.max.y) == IEFileReadError) {
                  HDR_LOG("There was a generic error on loading the EXR image \"%s\". Image could be corrupted.", filename);
                  return (IEFileReadError);
              }
  
              image-&gt;unproc = 1;
  
              return (IENoError);
          } else {
              char sChannels[2048] = { '\0' };
  
              for (ChannelList::ConstIterator it = iHeader.channels().begin(), ite = iHeader.channels().end(); it != ite; it++) {
                  strcat(sChannels, it.name());
                  strcat(sChannels, " ");
              }
  
              HDR_LOG("Unable to open EXR file (unknown channels set: %s)", sChannels);
              return (IEFileReadError);
          }
      }
  </code></pre>
  
  <p>But I wonder how this library could decode/transform Y-RY-GY images (luminance + chroma channels) and get floating point RGB pixel data.</p>