Correct color for RGB14v3 messages

[stijn-vranckx]

I compared the behavior with the original C++ code.
The context object is adapted there in the LASreadItemCompressed_POINT14_v3::read and LASreadItemCompressed_POINT14_v4::init methods.

The CompressionContext seems to be the work around here since we can not adapted the context value itself. But I think this should be static.

Also the C++ code contains the following:

inline void LASreadItemCompressed_RGB14_v3::read(U8* item, U32& context)
{
  // get last

  U16* last_item = contexts[current_context].last_item;

  // check for context switch

  if (current_context != context)
  {
    current_context = context; // all other items use context set by POINT14 reader
    if (contexts[current_context].unused)
    {
      createAndInitModelsAndDecompressors(current_context, (U8*)last_item);
      last_item = contexts[current_context].last_item;
    }
  }

having both lines in the if block.

I discovered the problem by unzipping a laz file with RGB14_v3 data with both LAStools and laszip4j and seeing different color values in the resulting las file.

[stijn-vranckx]

The following zip contains a laz file that illustrates the problem. The resulting las file will be different when using LASTools and laszip4j.

500m_5460_59370_IM2023_subset.zip

[mreutegg]

I'm closing this PR in favor of #143.