some more lines in manual mode

diff --git a/manual.py b/manual.py
index a2c4f50..0ec6412 100644 (file)
--- a/manual.py
+++ b/manual.py
@@ -53,5 +53,39 @@ def find_lines(im_orig):
                                   width=line_width)
                         draw.line((corners[3], corners[0]), fill=color,
                                   width=line_width)
+                        l1 = half_line(corners)
+                        draw.line(l1, fill=color, width=line_width)
+                        l2 = half_line(corners[1:4] + [corners[0]])
+                        draw.line(l2, fill=color, width=line_width)
+                        c = center(corners)
+                        draw.ellipse((c[0] - 1, c[1] - 1, c[0] + 1, c[1] + 1),
+                                     fill=(255, 64, 64))
+
         screen.display_picture(im)
         clock.tick(15)
+
+def half_line(corners):
+    c = center(corners)
+    d1 = intersection(line(corners[0], corners[3]),
+                      line(corners[1], corners[2]))
+    p1 = intersection(line(c,d1), line(corners[0],
+                                      corners[1]))
+    p2 = intersection(line(c,d1), line(corners[2],
+                                      corners[3]))
+    return (p1, p2)
+
+def center(corners):
+    return intersection(line(corners[0], corners[2]), line(corners[1],
+                                                           corners[3]))
+def line(x, y):
+    a = float(x[1] - y[1])
+    b = float(y[0] - x[0])
+    c = a * y[0] + b * y[1]
+    return (a, b, c)
+
+def intersection(p, q):
+    det = p[0] * q[1] - p[1] * q[0]
+    if det == 0:
+        return None
+    return (int(round((q[1] * p[2] - p[1] * q[2]) / det)), int(round((p[0] *
+                                                q[2] - q[0] * p[2]) / det)))