code: private int[] makeUVCoordDeltas(AttributeData map, SortableVertex[] sortVertices) {
          // UV coordinate scaling factor
          float scale = 1.0f / map.precision;
          int vc = sortVertices.length;
          int prevU = 0, prevV = 0;
          int[] intUVCoords = new int[vc * CTM_UV_ELEMENT_COUNT];
          for (int i = 0; i < vc; ++i) {
              // Get old UV coordinate index (before vertex sorting)
              int oldIdx = sortVertices[i].originalIndex;
  
              // Convert to fixed point
              int u = (int) floor(scale * map.values[oldIdx * 2] + 0.5f);
              int v = (int) floor(scale * map.values[oldIdx * 2 + 1] + 0.5f);
  
              // Calculate delta and store it in the converted array. NOTE: Here we rely
              // on the fact that vertices are sorted, and usually close to each other,
              // which means that UV coordinates should also be close to each other...
              intUVCoords[i * 2] = u - prevU;
              intUVCoords[i * 2 + 1] = v - prevV;
  
              prevU = u;
              prevV = v;
          }
          return intUVCoords;
      }
docs: Calculate various forms of derivatives in order to reduce data entropy.
  
  @param map attributes
  @param sortVertices sorted vertices
  @return encoded UV data