attr: change RGB coding order to GBR

The GBR coding order matches the description in ISO/IEC 23001-8 for
the identity matrix (MatrixCoefficients=0).

tmc3/PCCMath.h

@@ -68,12 +68,7 @@ public:
     return data[i];
   }
   size_t getElementCount() const { return 3; }
-  T& r() { return data[0]; }
-  T& g() { return data[1]; }
-  T& b() { return data[2]; }
-  const T& r() const { return data[0]; }
-  const T& g() const { return data[1]; }
-  const T& b() const { return data[2]; }
+
   T& x() { return data[0]; }
   T& y() { return data[1]; }
   T& z() { return data[2]; }

tmc3/PCCPointSet.h

@@ -494,9 +494,9 @@ public:
   void convertRGBToYUV()
   {  // BT709
     for (auto& color : colors) {
-      const uint8_t r = color[0];
-      const uint8_t g = color[1];
-      const uint8_t b = color[2];
+      const uint8_t r = color[2];
+      const uint8_t g = color[0];
+      const uint8_t b = color[1];
       const double y = PCCClip(
         std::round(0.212600 * r + 0.715200 * g + 0.072200 * b), 0., 255.);
       const double u = PCCClip(
@@ -521,9 +521,9 @@ public:
         PCCClip(round(y1 - 0.18733 * u1 - 0.46813 * v1), 0.0, 255.0);
       const double b =
         PCCClip(round(y1 + 1.85563 * u1 /*+ 0.00000 * v1*/), 0.0, 255.0);
-      color[0] = static_cast<uint8_t>(r);
-      color[1] = static_cast<uint8_t>(g);
-      color[2] = static_cast<uint8_t>(b);
+      color[2] = static_cast<uint8_t>(r);
+      color[0] = static_cast<uint8_t>(g);
+      color[1] = static_cast<uint8_t>(b);
     }
   }
 

tmc3/ply.cpp

@@ -122,9 +122,9 @@ ply::write(
   }
 
   if (cloud.hasColors()) {
-    fout << "property uchar red" << std::endl;
     fout << "property uchar green" << std::endl;
     fout << "property uchar blue" << std::endl;
+    fout << "property uchar red" << std::endl;
   }
   if (cloud.hasReflectances()) {
     fout << "property uint16 refc" << std::endl;
@@ -396,9 +396,9 @@ ply::read(
       position[2] = atof(tokens[indexZ].c_str());
       if (cloud.hasColors()) {
         auto& color = cloud.getColor(pointCounter);
-        color[0] = atoi(tokens[indexR].c_str());
-        color[1] = atoi(tokens[indexG].c_str());
-        color[2] = atoi(tokens[indexB].c_str());
+        color[0] = atoi(tokens[indexG].c_str());
+        color[1] = atoi(tokens[indexB].c_str());
+        color[2] = atoi(tokens[indexR].c_str());
       }
       if (cloud.hasReflectances()) {
         cloud.getReflectance(pointCounter) =
@@ -448,13 +448,13 @@ ply::read(
           }
         } else if (a == indexR && attributeInfo.byteCount == 1) {
           auto& color = cloud.getColor(pointCounter);
-          ifs.read(reinterpret_cast<char*>(&color[0]), sizeof(uint8_t));
+          ifs.read(reinterpret_cast<char*>(&color[2]), sizeof(uint8_t));
         } else if (a == indexG && attributeInfo.byteCount == 1) {
           auto& color = cloud.getColor(pointCounter);
-          ifs.read(reinterpret_cast<char*>(&color[1]), sizeof(uint8_t));
+          ifs.read(reinterpret_cast<char*>(&color[0]), sizeof(uint8_t));
         } else if (a == indexB && attributeInfo.byteCount == 1) {
           auto& color = cloud.getColor(pointCounter);
-          ifs.read(reinterpret_cast<char*>(&color[2]), sizeof(uint8_t));
+          ifs.read(reinterpret_cast<char*>(&color[1]), sizeof(uint8_t));
         } else if (a == indexReflectance && attributeInfo.byteCount <= 2) {
           if (attributeInfo.byteCount == 1) {
             uint8_t reflectance;