add example to mesh gray image with custom initialization

Mesh_3/examples/Mesh_3/CMakeLists.txt

@@ -149,6 +149,11 @@ if(TARGET CGAL::CGAL_ImageIO)
     target_link_libraries(mesh_3D_image_with_custom_initialization
                           PUBLIC CGAL::Eigen3_support)
 
+    create_single_source_cgal_program(
+      "mesh_3D_gray_image_with_custom_initialization.cpp")
+    target_link_libraries(mesh_3D_image_with_custom_initialization
+                          PUBLIC CGAL::Eigen3_support)
+
     create_single_source_cgal_program("mesh_3D_image_variable_size.cpp")
     target_link_libraries(mesh_3D_image_variable_size
                           PUBLIC CGAL::Eigen3_support)

Mesh_3/examples/Mesh_3/mesh_3D_gray_image_with_custom_initialization.cpp

@@ -0,0 +1,71 @@
+
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+
+#include <CGAL/Mesh_triangulation_3.h>
+#include <CGAL/Mesh_complex_3_in_triangulation_3.h>
+#include <CGAL/Mesh_criteria_3.h>
+
+#include <CGAL/Mesh_3/initialize_triangulation_from_gray_image.h>
+
+#include <CGAL/Labeled_mesh_domain_3.h>
+#include <CGAL/make_mesh_3.h>
+#include <CGAL/Image_3.h>
+#include <functional>
+
+typedef float Image_word_type;
+
+// Domain
+typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
+typedef CGAL::Labeled_mesh_domain_3<K> Mesh_domain;
+
+// Parallel tag
+#ifdef CGAL_CONCURRENT_MESH_3
+typedef CGAL::Parallel_tag Concurrency_tag;
+#else
+typedef CGAL::Sequential_tag Concurrency_tag;
+#endif
+
+// Triangulation
+typedef CGAL::Mesh_triangulation_3<Mesh_domain, CGAL::Default, Concurrency_tag>::type Tr;
+typedef CGAL::Mesh_complex_3_in_triangulation_3<Tr> C3t3;
+
+// Criteria
+typedef CGAL::Mesh_criteria_3<Tr> Mesh_criteria;
+
+// To avoid verbose function and named parameters call
+using namespace CGAL::parameters;
+
+int main(int argc, char* argv[])
+{
+  const char* fname = (argc > 1) ? argv[1] : "data/skull_2.9.inr";
+  /// [Load image]
+  CGAL::Image_3 image;
+  if (!image.read(fname)) {
+    std::cerr << "Error: Cannot read file " << fname << std::endl;
+    return EXIT_FAILURE;
+  }
+  /// [Domain creation]
+  Mesh_domain domain =
+    Mesh_domain::create_gray_image_mesh_domain(image, 2.9f, 0.f);
+  /// [Domain creation]
+
+  /// [Mesh criteria]
+  Mesh_criteria criteria(facet_angle = 30, facet_size = 6, facet_distance = 2,
+    cell_radius_edge_ratio = 3, cell_size = 8);
+
+  /// [Meshing]
+  C3t3 c3t3;
+  initialize_triangulation_from_gray_image(c3t3,
+                                           domain,
+                                           image,
+                                           criteria,
+                                           2.9f,
+                                           Image_word_type(0));
+  CGAL::refine_mesh_3(c3t3, domain, criteria);
+  /// [Meshing]
+
+  /// Output
+  CGAL::dump_c3t3(c3t3, "out");
+
+  return 0;
+}