Add condition option to assign filter

Values will only be assigned when the condition (specified as a DimRange) is
met.

Closes #1956

filters/AssignFilter.cpp

@@ -123,13 +123,20 @@ void AssignFilter::addArgs(ProgramArgs& args)
 {
     args.add("assignment", "Values to assign to dimensions based on range.",
         m_assignments);
+    args.add("condition", "Condition for assignment based on range.",
+        m_condition);
 }
 
 
 void AssignFilter::prepared(PointTableRef table)
 {
     PointLayoutPtr layout(table.layout());
 
+    m_condition.m_id = layout->findDim(m_condition.m_name);
+    if (m_condition.m_id == Dimension::Id::Unknown)
+        throwError("Invalid dimension name in 'condition' option: '" +
+            m_condition.m_name + "'.");
+
     for (auto& r : m_assignments)
     {
         r.m_id = layout->findDim(r.m_name);
@@ -143,7 +150,8 @@ void AssignFilter::prepared(PointTableRef table)
 bool AssignFilter::processOne(PointRef& point)
 {
     for (AssignRange& r : m_assignments)
-        if (r.valuePasses(point.getFieldAs<double>(r.m_id)))
+        if (r.valuePasses(point.getFieldAs<double>(r.m_id)) &&
+            m_condition.valuePasses(point.getFieldAs<double>(m_condition.m_id)))
             point.setField(r.m_id, r.m_value);
     return true;
 }

filters/AssignFilter.hpp

@@ -37,6 +37,8 @@
 #include <pdal/Filter.hpp>
 #include <pdal/Streamable.hpp>
 
+#include "private/DimRange.hpp"
+
 namespace pdal
 {
 
@@ -60,6 +62,7 @@ class PDAL_DLL AssignFilter : public Filter, public Streamable
     AssignFilter(const AssignFilter&) = delete;
 
     std::vector<AssignRange> m_assignments;
+    DimRange m_condition;
 };
 
 } // namespace pdal