refactoring MarchingSquares::RunMarchingSquares, merging lines part1

lib/qtgraph/marching_squares.cpp

@@ -6,6 +6,35 @@
 
 #include <png++/png.hpp>
 
+// #include <bitset>
+#include <iostream>
+
+namespace {
+
+  struct int2 {
+    int x, y;
+    constexpr int2 (int _x, int _y) : x(_x), y(_y) {}
+    int2 (const int2& o) : x(o.x), y(o.y) {}
+  };
+  int2 operator+(const int2& a, const int2& b) { return int2(a.x+b.x, a.y+b.y); }
+  float2 operator+(const float2& f, const int2& i) { return float2(f.x+i.x, f.y+i.y); }
+
+  inline int getMaskAt(const std::vector< MarchingSquares::CellType >& cells, int width, int2 point) {
+    const int x = point.x;
+    const int y = point.y;
+    const MarchingSquares::CellType quad[4] = {
+        cells[(y-1) * width + (x-1)], cells[(y-1) * width + x],   // TL T
+        cells[    y * width + (x-1)], cells[    y * width + x] }; // R  X
+
+    const int mask = ((quad[0] == MarchingSquares::FREE) ? 0x0 : 0x1)
+                   | ((quad[1] == MarchingSquares::FREE) ? 0x0 : 0x2)
+                   | ((quad[2] == MarchingSquares::FREE) ? 0x0 : 0x4)
+                   | ((quad[3] == MarchingSquares::FREE) ? 0x0 : 0x8);
+
+    return mask;
+  }
+}
+
 MarchingSquares::MarchingSquares()
   : width_(0)
   , height_(0)
@@ -53,22 +82,36 @@ MarchingSquares::RunMarchingSquares() {
         float2(-1,    -0.5f)  // L  7
       };
 
-  constexpr float2 center(0.5, 0.5);
+  constexpr int2 step[16] = { // clockwise, starting in top-left corner
+        int2(0, 0), // 0x0
+        int2(1, 1), // 0x1
+        int2(-1, 1), // 0x2
+        int2(1, 0), // 0x3
+        int2(-1, 1), // 0x4
+        int2(0, 1), // 0x5
+        int2(0, 0), // 0x6
+        int2(0, 0), // 0x7
+        int2(1, 1), // 0x8
+        int2(0, 0), // 0x9
+        int2(0, 1), // 0xa
+        int2(0, 0), // 0xb
+        int2(1, 0), // 0xc
+        int2(0, 0), // 0xd
+        int2(0, 0), // 0xe
+        int2(0, 0) // 0xf
+      };
 
-  std::vector< std::pair<float2, float2> > lines;
+  constexpr float2 center(0.5, 0.5);
-  for (size_t y = 1; y < height_; ++y) {
-    for (size_t x = 1; x < width_; ++x) {
 
-      const CellType quad[4] = {
+  const int number_of_cells = width_*height_;
-        cells_[(y-1) * width_ + (x-1)], cells_[(y-1) * width_ + x],   // TL T
+  std::vector<bool> visited(number_of_cells, false);
-        cells_[    y * width_ + (x-1)], cells_[    y * width_ + x] }; // R  X
 
-      const int mask = ((quad[0] == FREE) ? 0x0 : 0x1)
+  std::vector< std::pair<float2, float2> > lines;
-                     | ((quad[1] == FREE) ? 0x0 : 0x2)
+  int2 point(1, 1);
-                     | ((quad[2] == FREE) ? 0x0 : 0x4)
+  for (point.y = 1 ;point.y < height_; ++point.y) {
-                     | ((quad[3] == FREE) ? 0x0 : 0x8);
+    for (point.x = 1; point.x < width_; ++point.x) {
 
-      const float2 point(x, y);
+      const int mask = getMaskAt(cells_, width_, point);
 
       // these are the marching squares cases
       int s = -1, e = -1;
@@ -76,14 +119,14 @@ MarchingSquares::RunMarchingSquares() {
         case 0x0: /* all free, nothing to do */      break;
 
         case 0x1: /* TL       = TL  */ s = 7; e = 1; break;
-        case 0x2: /*   TR     = TR  */ s = 1; e = 3; break;
+        case 0x2: /*   TR     = TR  */ s = 3; e = 1; break;
         case 0x4: /*     BL   = BL  */ s = 5; e = 7; break;
-        case 0x8: /*       BR = BR  */ s = 3; e = 5; break;
+        case 0x8: /*       BR = BR  */ s = 5; e = 3; break;
 
         case 0x3: /* TLTR     = top    */ s = 7; e = 3; break;
         case 0x5: /* TL  BL   = left   */ s = 1; e = 5; break;
-        case 0xa: /*   TR  BR = right  */ s = 5; e = 1; break;
+        case 0xa: /*   TR  BR = right  */ s = 1; e = 5; break;
-        case 0xc: /*     BLBR = bottom */ s = 3; e = 7; break;
+        case 0xc: /*     BLBR = bottom */ s = 7; e = 3; break;
 
         // two lines
         case 0x6: /*   TRBL   = left desc diagonal */ s = 1 | 5 << 4; e = 3 | 7 << 4; break;
@@ -97,12 +140,38 @@ MarchingSquares::RunMarchingSquares() {
         case 0xf: /* all blocked, nothing to do */       break;
       }
 
+      std::cout << mask << " ";
+
+      if (visited[point.y*width_ + point.x] == true)
+        continue;
+
       if (s == -1) {
         // assert: e == -1
       }
+
+//       if (mask == 0x7)
+//         continue;
+
       else if ((s & 0xf) == s) {
         // assert: (e & 0xf) == e
-        lines.push_back(std::pair<float2, float2>(points[s]+center+point, points[e]+center+point));
+//         lines.push_back(std::pair<float2, float2>(points[s]+center+point, points[e]+center+point));
+
+        if (mask == 0x3 || mask == 0x5 || mask == 0xa || mask == 0xc
+//            || mask == 0x1 || mask == 0x2 || mask == 0x4 || mask == 0x8
+           ) {
+          int2 i = point;
+          while (true) {
+            int2 next = i + step[mask];
+            if (next.x < width_ && point.y < height_ && getMaskAt(cells_, width_, next) == mask && visited[next.y*width_ + next.x] == false) {
+              visited[next.y*width_ + next.x] = true;
+              i = next;
+            } else
+              break;
+          }
+          lines.push_back(std::pair<float2, float2>(points[s]+center+point, points[e]+center+i));
+        }
+        else
+          lines.push_back(std::pair<float2, float2>(points[s]+center+point, points[e]+center+point));
       }
       else {
         int s1 = s & 0xf, e1 = e & 0xf;
@@ -110,7 +179,10 @@ MarchingSquares::RunMarchingSquares() {
         lines.push_back(std::pair<float2, float2>(points[s1]+center+point, points[e1]+center+point));
         lines.push_back(std::pair<float2, float2>(points[s2]+center+point, points[e2]+center+point));
       }
+
+      visited[point.y*width_ + point.x] = true;
     }
+    std::cout << std::endl;
   }
 
   // build quadtree and combine lines (there are many, many small pieces around now, combine to longer lines)

lib/qtgraph/marching_squares.hpp

@@ -7,9 +7,10 @@
 class float2;
 
 class MarchingSquares {
-  enum CellType { FREE, SOLID, DESTROYABLE };
 
 public:
+  enum CellType { FREE, SOLID, DESTROYABLE };
+
   MarchingSquares();
 
   void ReadImage(const std::string& filename);