A-M baby

Task/Hough-transform/Python/hough-transform.py

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+from math import hypot, pi, cos, sin
+import Image
+
+
+def hough(im, ntx=460, mry=360):
+    "Calculate Hough transform."
+    pim = im.load()
+    nimx, mimy = im.size
+    mry = int(mry/2)*2          #Make sure that this is even
+    him = Image.new("L", (ntx, mry), 255)
+    phim = him.load()
+
+    rmax = hypot(nimx, mimy)
+    dr = rmax / (mry/2)
+    dth = pi / ntx
+
+    for jx in xrange(nimx):
+        for iy in xrange(mimy):
+            col = pim[jx, iy]
+            if col == 255: continue
+            for jtx in xrange(ntx):
+                th = dth * jtx
+                r = jx*cos(th) + iy*sin(th)
+                iry = mry/2 + int(r/dr+0.5)
+                phim[jtx, iry] -= 1
+    return him
+
+
+def test():
+    "Test Hough transform with pentagon."
+    im = Image.open("pentagon.png").convert("L")
+    him = hough(im)
+    him.save("ho5.bmp")
+
+
+if __name__ == "__main__": test()