extract continuous lines from the conrec code (#6676)

Code/Numerics/testConrec.cpp

@@ -1,5 +1,5 @@
 //
-//  Copyright (C) 2019 Greg Landrum
+//  Copyright (C) 2019-2023 Greg Landrum
 //
 //   @@ All Rights Reserved @@
 //  This file is part of the RDKit.
@@ -23,7 +23,149 @@ TEST_CASE("Conrec basics", "[conrec]") {
   SECTION("basics") {
     std::vector<RDGeom::Point2D> pts = {{0., 0.}, {1., 0.}, {1., 1.}, {0., 1.}};
     const size_t gridSz = 100;
-    auto *grid = new double[gridSz * gridSz];
+    auto grid = std::make_unique<double[]>(gridSz * gridSz);
+    double xps[gridSz];
+    double yps[gridSz];
+    double x1 = -4, y1 = -4, x2 = 6, y2 = 6;
+    double dx = (x2 - x1) / gridSz, dy = (y2 - y1) / gridSz;
+    double maxV = 0.0;
+    for (size_t ix = 0; ix < gridSz; ++ix) {
+      auto px = x1 + ix * dx;
+      xps[ix] = px;
+      for (size_t iy = 0; iy < gridSz; ++iy) {
+        auto py = y1 + iy * dy;
+        if (ix == 0) {
+          yps[iy] = py;
+        }
+        RDGeom::Point2D loc(px, py);
+        double val = 0.0;
+        for (const auto &pt : pts) {
+          auto dv = loc - pt;
+          auto r = dv.length();
+          if (r > 0) {
+            val += 1 / r;
+          }
+        }
+        // to make the contours more visible, we cap the max val we set at 1000
+        maxV = std::max(std::min(val, 1000.), maxV);
+        grid[ix * gridSz + iy] = val;
+      }
+    }
+    std::vector<conrec::ConrecSegment> segs;
+    const size_t nContours = 10;
+    double isoLevels[nContours];
+    for (size_t i = 0; i < nContours; ++i) {
+      isoLevels[i] = (i + 1) * (maxV / (nContours + 1));
+    }
+    conrec::Contour(grid.get(), 0, gridSz - 1, 0, gridSz - 1, xps, yps,
+                    nContours, isoLevels, segs);
+
+    std::ofstream outs("./blah.svg");
+    outs << R"SVG(<?xml version='1.0' encoding='iso-8859-1'?>
+<svg version='1.1' baseProfile='full'
+              xmlns='http://www.w3.org/2000/svg'
+                      xmlns:rdkit='http://www.rdkit.org/xml'
+                      xmlns:xlink='http://www.w3.org/1999/xlink'
+                  xml:space='preserve'
+width='300px' height='300px' >
+<rect style='opacity:1.0;fill:#FFFFFF;stroke:none' width='300' height='300' x='0' y='0'> </rect>
+<!-- END OF HEADER -->
+)SVG";
+    for (const auto &seg : segs) {
+      outs << "<path d='M " << 40 * seg.p1.x + 150 << "," << 40 * seg.p1.y + 150
+           << " " << 40 * seg.p2.x + 150 << "," << 40 * seg.p2.y + 150
+           << "' "
+              "style='fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:"
+              "0.5px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:"
+              "1' "
+              "/>"
+           << std::endl;
+      ;
+    }
+    outs << "</svg>" << std::endl;
+  }
+}
+
+TEST_CASE("connectLineSegments", "[conrec]") {
+  SECTION("basics") {
+    std::vector<RDGeom::Point2D> pts = {{0., 0.}, {1., 0.}, {1., 1.}, {0., 1.}};
+    const size_t gridSz = 100;
+    auto grid = std::make_unique<double[]>(gridSz * gridSz);
+    double xps[gridSz];
+    double yps[gridSz];
+    double x1 = -4, y1 = -4, x2 = 6, y2 = 6;
+    double dx = (x2 - x1) / gridSz, dy = (y2 - y1) / gridSz;
+    double maxV = 0.0;
+    for (size_t ix = 0; ix < gridSz; ++ix) {
+      auto px = x1 + ix * dx;
+      xps[ix] = px;
+      for (size_t iy = 0; iy < gridSz; ++iy) {
+        auto py = y1 + iy * dy;
+        if (ix == 0) {
+          yps[iy] = py;
+        }
+        RDGeom::Point2D loc(px, py);
+        double val = 0.0;
+        for (const auto &pt : pts) {
+          auto dv = loc - pt;
+          auto r = dv.length();
+          if (r > 0) {
+            val += 1 / r;
+          }
+        }
+        maxV = std::max(std::min(val, 1000.), maxV);
+        grid[ix * gridSz + iy] = val;
+      }
+    }
+    std::vector<conrec::ConrecSegment> segs;
+    const size_t nContours = 10;
+    double isoLevels[nContours];
+    for (size_t i = 0; i < nContours; ++i) {
+      isoLevels[i] = (i + 1) * (maxV / (nContours + 1));
+    }
+    conrec::Contour(grid.get(), 0, gridSz - 1, 0, gridSz - 1, xps, yps,
+                    nContours, isoLevels, segs);
+
+    auto contours = conrec::connectLineSegments(segs);
+    CHECK(contours.size() == 74);
+
+    std::ofstream outs("./blah.contour.svg");
+    outs << R"SVG(<?xml version='1.0' encoding='iso-8859-1'?>
+<svg version='1.1' baseProfile='full'
+              xmlns='http://www.w3.org/2000/svg'
+                      xmlns:rdkit='http://www.rdkit.org/xml'
+                      xmlns:xlink='http://www.w3.org/1999/xlink'
+                  xml:space='preserve'
+width='300px' height='300px' >
+<rect style='opacity:1.0;fill:#FFFFFF;stroke:none' width='300' height='300' x='0' y='0'> </rect>
+<!-- END OF HEADER -->
+)SVG";
+    for (const auto &pr : contours) {
+      auto [contour, val] = pr;
+      REQUIRE(contour.size());
+      outs << "<path d='M " << 40 * contour[0].x + 150 << ","
+           << 40 * contour[0].y + 150;
+      for (auto i = 1u; i < contour.size(); ++i) {
+        outs << " L " << 40 * contour[i].x + 150 << ","
+             << 40 * contour[i].y + 150;
+      }
+      outs << "' "
+              "style='fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:"
+              "0.5px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:"
+              "1' "
+              "/>"
+           << std::endl;
+    }
+    outs << "</svg>" << std::endl;
+  }
+}
+
+TEST_CASE("super chunky", "[conrec]") {
+  // an example where you can really see any holes in the contours
+  SECTION("basics") {
+    std::vector<RDGeom::Point2D> pts = {{0., 0.}, {1., 0.}, {1., 1.}, {0., 1.}};
+    const size_t gridSz = 5;
+    auto grid = std::make_unique<double[]>(gridSz * gridSz);
     double xps[gridSz];
     double yps[gridSz];
     double x1 = -4, y1 = -4, x2 = 6, y2 = 6;
@@ -51,15 +193,16 @@ TEST_CASE("Conrec basics", "[conrec]") {
       }
     }
     std::vector<conrec::ConrecSegment> segs;
-    const size_t nContours = 10;
+    const size_t nContours = 1;
     double isoLevels[nContours];
     for (size_t i = 0; i < nContours; ++i) {
       isoLevels[i] = (i + 1) * (maxV / (nContours + 1));
     }
-    conrec::Contour(grid, 0, gridSz - 1, 0, gridSz - 1, xps, yps, nContours,
-                    isoLevels, segs);
 
-    std::ofstream outs("./blah.svg");
+    conrec::Contour(grid.get(), 0, gridSz - 1, 0, gridSz - 1, xps, yps,
+                    nContours, isoLevels, segs);
+
+    std::ofstream outs("./chunky.svg");
     outs << R"SVG(<?xml version='1.0' encoding='iso-8859-1'?>
 <svg version='1.1' baseProfile='full'
               xmlns='http://www.w3.org/2000/svg'
@@ -82,6 +225,35 @@ width='300px' height='300px' >
       ;
     }
     outs << "</svg>" << std::endl;
-    delete[] grid;
+
+    auto contours = conrec::connectLineSegments(segs);
+    std::ofstream outs2("./chunky.contour.svg");
+    outs2 << R"SVG(<?xml version='1.0' encoding='iso-8859-1'?>
+<svg version='1.1' baseProfile='full'
+              xmlns='http://www.w3.org/2000/svg'
+                      xmlns:rdkit='http://www.rdkit.org/xml'
+                      xmlns:xlink='http://www.w3.org/1999/xlink'
+                  xml:space='preserve'
+width='300px' height='300px' >
+<rect style='opacity:1.0;fill:#FFFFFF;stroke:none' width='300' height='300' x='0' y='0'> </rect>
+<!-- END OF HEADER -->
+)SVG";
+    for (const auto &pr : contours) {
+      auto [contour, val] = pr;
+      REQUIRE(contour.size());
+      outs2 << "<path d='M " << 40 * contour[0].x + 150 << ","
+            << 40 * contour[0].y + 150;
+      for (auto i = 1u; i < contour.size(); ++i) {
+        outs2 << " L " << 40 * contour[i].x + 150 << ","
+              << 40 * contour[i].y + 150;
+      }
+      outs2 << "' "
+               "style='fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:"
+               "0.5px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:"
+               "1' "
+               "/>"
+            << std::endl;
+    }
+    outs2 << "</svg>" << std::endl;
   }
 }