From b9240bfef012c4bda96a74d9e3d0f5b53c1c56c0 Mon Sep 17 00:00:00 2001
From: Alexandre B A Villares <abav@lugaralgum.com>
Date: Wed, 17 Oct 2018 01:00:54 -0300
Subject: [PATCH] 291

---
 s291/s291.pyde | 114 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 s291/s291.pyde

diff --git a/s291/s291.pyde b/s291/s291.pyde
new file mode 100644
index 00000000..5579f915
--- /dev/null
+++ b/s291/s291.pyde
@@ -0,0 +1,114 @@
+# Alexandre B A Villares - https://abav.lugaralgum.com/sketch-a-day
+SKETCH_NAME = "s291"  # 20181016
+OUTPUT = ".gif"
+
+NUM = 10 
+BORDER = 50
+SPACING = 20
+
+def setup():
+    size(500, 500)
+    frameRate(5 )
+    create_points()
+    
+def create_points():
+    global points
+    points = [PVector(random(BORDER, width - BORDER),
+                      random(BORDER, height - BORDER))
+              for _ in range(NUM)]
+
+def draw():  
+    fill(200)
+    stroke(0)
+    rect(0, 0, width, height)
+    strokeWeight(2)
+    noFill()
+    beginShape()
+    for p in points:
+         vertex(p.x, p.y)
+    endShape(CLOSE)
+
+    stroke(0, 0, 100)
+    for x in range(0, width, SPACING):
+           a = PVector(x, 0)
+           b = PVector(x, height)
+           inter_line(points, Line(a, b))
+    
+    stroke(100, 0, 0)
+    for y in range(0, height, SPACING):
+           a = PVector(0, y)
+           b = PVector(width, y)
+           inter_line(points, Line(a, b))
+    
+
+
+def inter_line(points, L):                         
+    edges = pairwise(points) + [(points[-1], points[0])]
+    inter_points = []
+    
+    for p1, p2 in edges:
+        inter = line_instersect(Line(p1, p2), L)
+        if inter:
+            inter_points.append(inter)
+            strokeWeight(7)
+            point(inter.x, inter.y)
+            
+    if len(inter_points) > 1:
+        possible = pairwise(inter_points) #+ [(inter_points[-1], inter_points[0])]
+        for p3, p4 in possible:
+                strokeWeight(1)
+                line(p3.x, p3.y, p4.x, p4.y)
+          
+    
+def keyPressed():
+    if key == " ": create_points()
+    if key == "s": saveFrame("###.png")
+        
+class Line():
+    """ I should change this to a named tuple... """
+    def __init__(self, p1, p2):
+        self.p1 = p1
+        self.p2 = p2
+    
+def line_instersect(line_a, line_b):     
+    """
+    code adapted from Bernardo Fontes 
+    https://github.com/berinhard/sketches/
+    """
+       
+    x1, y1 = line_a.p1.x, line_a.p1.y
+    x2, y2 = line_a.p2.x, line_a.p2.y
+    x3, y3 = line_b.p1.x, line_b.p1.y
+    x4, y4 = line_b.p2.x, line_b.p2.y
+        
+    try:
+        uA = ((x4-x3)*(y1-y3) - (y4-y3)*(x1-x3)) / ((y4-y3)*(x2-x1) - (x4-x3)*(y2-y1));
+        uB = ((x2-x1)*(y1-y3) - (y2-y1)*(x1-x3)) / ((y4-y3)*(x2-x1) - (x4-x3)*(y2-y1));
+    except ZeroDivisionError:
+        return 
+        
+    if not(0 <= uA <= 1 and 0 <= uB <= 1):
+        return
+        
+    x = line_a.p1.x + uA * (line_a.p2.x - line_a.p1.x)
+    y = line_a.p1.y + uA * (line_a.p2.y - line_a.p1.y)
+        
+    return PVector(x, y)
+
+
+def pairwise(iterable):
+    import itertools
+    "s -> (s0,s1), (s1,s2), (s2, s3), ..."
+    a, b = itertools.tee(iterable)
+    next(b, None)
+    return zip(a, b) 
+
+# print text to add to the project's README.md             
+def settings():
+    println(
+"""
+![{0}]({0}/{0}{2})
+
+{1}: [code](https://github.com/villares/sketch-a-day/tree/master/{0}) [[Py.Processing](https://villares.github.io/como-instalar-o-processing-modo-python/index-EN)]
+""".format(SKETCH_NAME, SKETCH_NAME[1:], OUTPUT)
+    )