# HG changeset patch
# User Laman
# Date 2019-01-19 11:07:09
# Node ID 4d9660f111e427d06b6822b6eb80894780d1ba58
# Parent  046759436f6e5b08b1ca8cd10cbf028a89c3e063

grid: refactored out transformation matrix construction

diff --git a/src/analyzer/grid.py b/src/analyzer/grid.py
--- a/src/analyzer/grid.py
+++ b/src/analyzer/grid.py
@@ -1,5 +1,6 @@
-import numpy
-from .epoint import EPoint
+import numpy as np
+
+from .epoint import EPoint,homogenize
 
 
 ## Projective transformation of a point with a matrix A.
@@ -8,7 +9,28 @@ from .epoint import EPoint
 #  
 #  @return transformed point as a numpy.array
 def transformPoint(point,A):
-	return (A*numpy.matrix(point).transpose()).getA1()
+	return (A*np.matrix(point).transpose()).getA1()
+
+
+def computeRectiMatrix(a,b,c,d):
+	"""Computes a matrix mapping a projective space to an affine space.
+	ABCD quadrangle gets transformed to a parallelogram.
+
+	:param a,b,c,d: projective points"""
+	# ad
+	# bc
+	p1=np.cross(a,b)
+	p2=np.cross(c,d)
+	# 32 bit int can overflow. keeping it reasonably small. might want to use a cleaner solution
+	vanish1=homogenize(np.cross(p1, p2))
+
+	p3=np.cross(a,d)
+	p4=np.cross(b,c)
+	vanish2=homogenize(np.cross(p3, p4))
+
+	horizon=homogenize(np.cross(vanish1, vanish2))
+
+	return np.matrix([horizon,[0,1,0],[0,0,1]])
 
 
 class Grid:
@@ -26,29 +48,12 @@ class Grid:
 	def __init__(self,corners):
 		# ad
 		# bc
-		a,b,c,d=[c.toProjective() for c in corners]
-
-		p1=numpy.cross(a,b)
-		p2=numpy.cross(c,d)
-		vanish1=numpy.cross(p1,p2)
-		# !! 32 bit int can overflow. keeping it reasonably small. might want to use a cleaner solution
-		vanish1=EPoint.fromProjective(vanish1).toProjective() # !! EPoint fails with point in infinity
+		a,b,c,d=(c.toProjective() for c in corners)
 
-		p3=numpy.cross(a,d)
-		p4=numpy.cross(b,c)
-		vanish2=numpy.cross(p3,p4)
-		vanish2=EPoint.fromProjective(vanish2).toProjective()
-
-		horizon=numpy.cross(vanish1,vanish2)
-
-		horizon=EPoint.fromProjective(horizon).toProjective()
-
-		rectiMatrix=numpy.matrix([horizon,[0,1,0],[0,0,1]])
-		rectiMatrixInv=numpy.linalg.inv(rectiMatrix)
-
+		rectiMatrix=computeRectiMatrix(a,b,c,d)
+		rectiMatrixInv=np.linalg.inv(rectiMatrix)
 
 		affineCorners=[EPoint.fromProjective(transformPoint(x,rectiMatrix)) for x in (a,b,c,d)]
-		x=[affineCorners[0]-affineCorners[3],affineCorners[1]-affineCorners[2],affineCorners[0]-affineCorners[1],affineCorners[3]-affineCorners[2]]
 
 		self.intersections=[]
 		boardSize=19