add image_fname string for caching the last active dump image filename pattern

src/dump_image.cpp

@@ -36,6 +36,8 @@
 #include "memory.h"
 #include "modify.h"
 #include "molecule.h"
+#include "output.h"
+#include "thermo.h"
 #include "tokenizer.h"
 #include "update.h"
 #include "variable.h"
@@ -498,6 +500,10 @@ void DumpImage::init_style()
 
   DumpCustom::init_style();
 
+  // cache dump image filename pattern for access through library interface.
+
+  if (multifile) output->thermo->set_image_fname(filename);
+
   // for grid output, find current ptr for compute or fix
   // check that fix frequency is acceptable
 

src/thermo.cpp

@@ -113,6 +113,7 @@ Thermo::Thermo(LAMMPS *_lmp, int narg, char **arg) :
   flushflag = 0;
   ntimestep = -1;
   nline = -1;
+  image_fname.clear();
 
   // set style and corresponding lineflag
   // custom style builds its own line of keywords, including wildcard expansion

src/thermo.h

@@ -42,14 +42,17 @@ class Thermo : protected Pointers {
   void compute(int);
   int evaluate_keyword(const std::string &, double *);
 
-  // for accessing cached thermo data
-  const int *get_nfield() const { return &nfield; }
+  // for accessing cached thermo and related data
   const int *get_line() const { return &nline; }
+  const char *get_image_fname() const { return image_fname.c_str(); }
+
+  const int *get_nfield() const { return &nfield; }
   const bigint *get_timestep() const { return &ntimestep; }
   const std::vector<multitype> &get_fields() const { return field_data; }
   const std::vector<std::string> &get_keywords() const { return keyword; }
 
   void set_line(int _nline) { nline = _nline; }
+  void set_image_fname(const std::string &fname) { image_fname = fname; }
 
  private:
   int nfield, nfield_initial;
@@ -75,6 +78,7 @@ class Thermo : protected Pointers {
   bigint natoms;
   bigint ntimestep;
   int nline;
+  std::string image_fname;
 
   // data used by routines that compute single values
   int ivalue;          // integer value to print