Line to line segment conversion

Author: RomanJuranek

pclines/utils.py

@@ -0,0 +1,44 @@
+import numpy as np
+
+
+def line_segments_from_homogeneous(lines, bbox):
+    x,y,w,h = bbox
+    
+    # Corner points
+    A = np.array([x,y,1])
+    B = np.array([x+w,y,1])
+    C = np.array([x+w,y+h,1])
+    D = np.array([x,y+h,1])
+
+    # Cross product of pairs of corner points
+    edges = [
+        np.cross(a,b) for a,b in [[A,B],[B,C],[C,D],[D,A]]
+    ]
+
+    # Cross product of line params with edges
+    intersections = [
+        np.cross(lines, e) for e in edges
+    ]
+
+    # Normalize
+    normalized = [
+        p[:,:2] / p[:,-1].reshape(-1,1) for p in intersections
+    ]
+
+    X = []
+    Y = []
+    
+    for p in zip(*normalized):
+        P = []
+        for (u,v) in p:
+            if (x <= u <= x+w) and (y <= v <= y+h):
+                P.append( (u,v) )
+        if len(P) == 2:
+            (x0,y0), (x1,y1) = P
+            X.append( (x0,x1) )
+            Y.append( (y0,y1) )
+        else:
+            X.append(None)
+            Y.append(None)
+
+    return X, Y