Fix PcdWriter compression option

Rearrange workflow for determining compression level
for option writers.pcd.compression. Previous version
set write method before the program arguments were
set! This resulted in always ascii compression.

This also fixes a potential free() error that can occur
when this writer is ran within a pipeline.

plugins/pcl/io/PcdWriter.cpp

@@ -1,5 +1,6 @@
 /******************************************************************************
 * Copyright (c) 2011, Brad Chambers (brad.chambers@gmail.com)
+* Copytight (c) 2016, Logan Byers (logan.c.byers@gmail.com)
 *
 * All rights reserved.
 *
@@ -63,9 +64,8 @@ std::string PcdWriter::getName() const { return s_info.name; }
 void PcdWriter::addArgs(ProgramArgs& args)
 {
 
-    std::string compression;
     args.add("filename", "Filename to write PCD file to", m_filename);
-    args.add("compression","Level of PCD compression to use (ascii, binary, compressed)", compression, "ascii");
+    args.add("compression", "Level of PCD compression to use (ascii, binary, compressed)", m_compression_string);
     args.add("xyz", "Write only XYZ dimensions?", m_xyz, false);
     args.add("subtract_minimum", "Set origin to minimum of XYZ dimension", m_subtract_minimum, true);
     args.add("offset_x", "Offset to be subtracted from XYZ position", m_offset_x, 0.0);
@@ -75,19 +75,6 @@ void PcdWriter::addArgs(ProgramArgs& args)
     args.add("scale_y", "Scale to divide from XYZ dimension", m_scale_y, 1.0);
     args.add("scale_z", "Scale to divide from XYZ dimension", m_scale_z, 1.0);
 
-    if (compression == "binary")
-    {
-      m_compression = 1;
-    }
-    else if (compression == "compressed")
-    {
-      m_compression = 2;
-    }
-    else  // including "ascii"
-    {
-      m_compression = 0;
-    }
-
 }
 
 void PcdWriter::write(const PointViewPtr view)

plugins/pcl/io/PcdWriter.hpp

@@ -1,5 +1,6 @@
 /******************************************************************************
 * Copyright (c) 2014, Brad Chambers (brad.chambers@gmail.com)
+* Copytight (c) 2016, Logan Byers (logan.c.byers@gmail.com)
 *
 * All rights reserved.
 *
@@ -67,6 +68,7 @@ class PDAL_DLL PcdWriter : public Writer
     inline void writeView(const PointViewPtr view); // implemented in header
 
     std::string m_filename;
+    std::string m_compression_string;
     uint8_t m_compression;
     bool m_xyz;
     bool m_subtract_minimum;
@@ -101,6 +103,20 @@ void PcdWriter::writeView(const PointViewPtr view)
     }
     pclsupport::PDALtoPCD(view, *cloud, bounds, m_scale_x, m_scale_y, m_scale_z);
     pcl::PCDWriter w;
+
+    if (m_compression_string == "binary")
+    {
+      m_compression = 1;
+    }
+    else if (m_compression_string == "compressed")
+    {
+      m_compression = 2;
+    }
+    else  // including "ascii"
+    {
+      m_compression = 0;
+    }
+
     switch (m_compression)
     {
         case 0 : w.writeASCII<PointT>(m_filename, *cloud); break;