Add support for PNG plots using libpng

CMakeLists.txt

@@ -79,6 +79,11 @@ if(libmesh)
   find_package(LIBMESH REQUIRED)
 endif()
 
+#===============================================================================
+# libpng
+#===============================================================================
+find_package(PNG)
+
 #===============================================================================
 # HDF5 for binary output
 #===============================================================================
@@ -423,6 +428,11 @@ if(libmesh)
   target_link_libraries(libopenmc PkgConfig::LIBMESH)
 endif()
 
+if (PNG_FOUND)
+  target_compile_definitions(libopenmc PRIVATE USE_LIBPNG)
+  target_link_libraries(libopenmc PNG::PNG)
+endif()
+
 #===============================================================================
 # openmc executable
 #===============================================================================

cmake/OpenMCConfig.cmake.in

@@ -16,6 +16,8 @@ if(@libmesh@)
   pkg_check_modules(LIBMESH REQUIRED @LIBMESH_PC_FILE@>=1.6.0 IMPORTED_TARGET)
 endif()
 
+find_package(PNG)
+
 if(NOT TARGET OpenMC::libopenmc)
   include("${OpenMC_CMAKE_DIR}/OpenMCTargets.cmake")
 endif()

include/openmc/plot.h

@@ -239,11 +239,18 @@ public:
 //! \param[out] image data associated with the plot object
 void draw_mesh_lines(Plot const& pl, ImageData& data);
 
-//! Write a ppm image to file using a plot object's image data
+//! Write a PPM image using a plot object's image data
 //! \param[in] plot object
 //! \param[out] image data associated with the plot object
 void output_ppm(Plot const& pl, const ImageData& data);
 
+#ifdef USE_LIBPNG
+//! Write a PNG image using a plot object's image data
+//! \param[in] plot object
+//! \param[out] image data associated with the plot object
+void output_png(Plot const& pl, const ImageData& data);
+#endif
+
 //! Initialize a voxel file
 //! \param[in] id of an open hdf5 file
 //! \param[in] dimensions of the voxel file (dx, dy, dz)
@@ -274,9 +281,9 @@ void voxel_finalize(hid_t dspace, hid_t dset, hid_t memspace);
 //! Read plot specifications from a plots.xml file
 void read_plots_xml();
 
-//! Create a ppm image for a plot object
+//! Create an image for a plot object
 //! \param[in] plot object
-void create_ppm(Plot const& pl);
+void create_image(Plot const& pl);
 
 //! Create an hdf5 voxel file for a plot object
 //! \param[in] plot object

src/plot.cpp

@@ -1,12 +1,16 @@
 #include "openmc/plot.h"
 
 #include <algorithm>
+#include <cstdio>
 #include <fstream>
 #include <sstream>
 
 #include "xtensor/xview.hpp"
 #include <fmt/core.h>
 #include <fmt/ostream.h>
+#ifdef USE_LIBPNG
+#include <png.h>
+#endif
 
 #include "openmc/constants.h"
 #include "openmc/error.h"
@@ -103,17 +107,19 @@ uint64_t plotter_seed = 1;
 
 extern "C" int openmc_plot_geometry()
 {
+
   for (auto& pl : model::plots) {
     write_message(5, "Processing plot {}: {}...", pl.id_, pl.path_plot_);
 
     if (PlotType::slice == pl.type_) {
       // create 2D image
-      create_ppm(pl);
+      create_image(pl);
     } else if (PlotType::voxel == pl.type_) {
       // create voxel file for 3D viewing
       create_voxel(pl);
     }
   }
+
   return 0;
 }
 
@@ -139,11 +145,11 @@ void read_plots_xml()
 }
 
 //==============================================================================
-// CREATE_PPM creates an image based on user input from a plots.xml <plot>
-// specification in the portable pixmap format (PPM)
+// CREATE_IMAGE creates an image based on user input from a plots.xml <plot>
+// specification in the PNG/PPM format
 //==============================================================================
 
-void create_ppm(Plot const& pl)
+void create_image(Plot const& pl)
 {
 
   size_t width = pl.pixels_[0];
@@ -184,8 +190,12 @@ void create_ppm(Plot const& pl)
     draw_mesh_lines(pl, data);
   }
 
-  // write ppm data to file
+// create image file
+#ifdef USE_LIBPNG
+  output_png(pl, data);
+#else
   output_ppm(pl, data);
+#endif
 }
 
 void Plot::set_id(pugi::xml_node plot_node)
@@ -238,7 +248,11 @@ void Plot::set_output_path(pugi::xml_node plot_node)
   // add appropriate file extension to name
   switch (type_) {
   case PlotType::slice:
+#ifdef USE_LIBPNG
+    filename.append(".png");
+#else
     filename.append(".ppm");
+#endif
     break;
   case PlotType::voxel:
     filename.append(".h5");
@@ -673,6 +687,60 @@ void output_ppm(Plot const& pl, const ImageData& data)
   of << "\n";
 }
 
+//==============================================================================
+// OUTPUT_PNG writes out a previously generated image to a PNG file
+//==============================================================================
+
+#ifdef USE_LIBPNG
+void output_png(Plot const& pl, const ImageData& data)
+{
+  // Open PNG file for writing
+  std::string fname = pl.path_plot_;
+  fname = strtrim(fname);
+  auto fp = std::fopen(fname.c_str(), "wb");
+
+  // Initialize write and info structures
+  auto png_ptr =
+    png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
+  auto info_ptr = png_create_info_struct(png_ptr);
+
+  // Setup exception handling
+  if (setjmp(png_jmpbuf(png_ptr)))
+    fatal_error("Error during png creation");
+
+  png_init_io(png_ptr, fp);
+
+  // Write header (8 bit colour depth)
+  int width = pl.pixels_[0];
+  int height = pl.pixels_[1];
+  png_set_IHDR(png_ptr, info_ptr, width, height, 8, PNG_COLOR_TYPE_RGB,
+    PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+  png_write_info(png_ptr, info_ptr);
+
+  // Allocate memory for one row (3 bytes per pixel - RGB)
+  std::vector<png_byte> row(3 * width);
+
+  // Write color for each pixel
+  for (int y = 0; y < height; y++) {
+    for (int x = 0; x < width; x++) {
+      RGBColor rgb = data(x, y);
+      row[3 * x] = rgb.red;
+      row[3 * x + 1] = rgb.green;
+      row[3 * x + 2] = rgb.blue;
+    }
+    png_write_row(png_ptr, row.data());
+  }
+
+  // End write
+  png_write_end(png_ptr, nullptr);
+
+  // Clean up data structures
+  std::fclose(fp);
+  png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);
+  png_destroy_write_struct(&png_ptr, nullptr);
+}
+#endif
+
 //==============================================================================
 // DRAW_MESH_LINES draws mesh line boundaries on an image
 //==============================================================================
@@ -777,7 +845,7 @@ void draw_mesh_lines(Plot const& pl, ImageData& data)
 
 //==============================================================================
 // CREATE_VOXEL outputs a binary file that can be input into silomesh for 3D
-// geometry visualization.  It works the same way as create_ppm by dragging a
+// geometry visualization.  It works the same way as create_image by dragging a
 // particle across the geometry for the specified number of voxels. The first 3
 // int's in the binary are the number of x, y, and z voxels.  The next 3
 // double's are the widths of the voxels in the x, y, and z directions. The

tests/regression_tests/plot/results_true.dat

@@ -1 +1 @@
-a8192f6029cf99748816fab2618fa48e180656eba313940ccdfff3e56890a5dadd13bf92cd7e3be6a4b535bca5e2a58a905fcfba018fb922273f8be6dfc19859
+f85c20735a0c08525fe48b19a8e075c074539ee6c8860268fa0cb515d842496b7086e5b94305ef78dcf2106bb193abdf438259ac8ff1d0245a2782eb6f5af873

tests/regression_tests/plot/test.py

@@ -19,7 +19,7 @@ class PlotTestHarness(TestHarness):
         openmc.plot_geometry(openmc_exec=config['exe'])
 
     def _test_output_created(self):
-        """Make sure *.ppm has been created."""
+        """Make sure *.png has been created."""
         for fname in self._plot_names:
             assert os.path.exists(fname), 'Plot output file does not exist.'
 
@@ -34,8 +34,8 @@ class PlotTestHarness(TestHarness):
         outstr = bytes()
 
         for fname in self._plot_names:
-            if fname.endswith('.ppm'):
-                # Add PPM output to results
+            if fname.endswith('.png'):
+                # Add PNG output to results
                 with open(fname, 'rb') as fh:
                     outstr += fh.read()
             elif fname.endswith('.h5'):
@@ -56,6 +56,6 @@ class PlotTestHarness(TestHarness):
 
 
 def test_plot():
-    harness = PlotTestHarness(('plot_1.ppm', 'plot_2.ppm', 'plot_3.ppm',
+    harness = PlotTestHarness(('plot_1.png', 'plot_2.png', 'plot_3.png',
                                'plot_4.h5'))
     harness.main()

tests/regression_tests/plot_overlaps/results_true.dat

@@ -1 +1 @@
-566103831cb8273b0578565c39d30e479664e2b1783d877b45b42cf4f3af0b01671b6db423114b09a74bbe1ddf51a7db565ff2118d6d1ee987b52318773b719a
+926065ceb2a9b8292fe6270317c38c4373473cfea19d2a8392a32e5ece8e314c04b9f032921d987bd195ae4b6f674d359b0e38302e6ae4c93b4ac9573a384ac6

tests/regression_tests/plot_overlaps/test.py

@@ -19,7 +19,7 @@ class PlotTestHarness(TestHarness):
         openmc.plot_geometry(openmc_exec=config['exe'])
 
     def _test_output_created(self):
-        """Make sure *.ppm has been created."""
+        """Make sure *.png has been created."""
         for fname in self._plot_names:
             assert os.path.exists(fname), 'Plot output file does not exist.'
 
@@ -34,8 +34,8 @@ class PlotTestHarness(TestHarness):
         outstr = bytes()
 
         for fname in self._plot_names:
-            if fname.endswith('.ppm'):
-                # Add PPM output to results
+            if fname.endswith('.png'):
+                # Add PNG output to results
                 with open(fname, 'rb') as fh:
                     outstr += fh.read()
             elif fname.endswith('.h5'):
@@ -56,6 +56,6 @@ class PlotTestHarness(TestHarness):
 
 
 def test_plot_overlap():
-    harness = PlotTestHarness(('plot_1.ppm', 'plot_2.ppm', 'plot_3.ppm',
+    harness = PlotTestHarness(('plot_1.png', 'plot_2.png', 'plot_3.png',
                                'plot_4.h5'))
     harness.main()

tests/regression_tests/plot_voxel/test.py

@@ -25,7 +25,7 @@ class PlotVoxelTestHarness(TestHarness):
                    glob.glob('plot_4.h5'))
 
     def _test_output_created(self):
-        """Make sure *.ppm has been created."""
+        """Make sure plots have been created."""
         for fname in self._plot_names:
             assert os.path.exists(fname), 'Plot output file does not exist.'