Merge pull request sebasvega95#1 from sebasvega95/maximum

added Non-maximum suppression

Author: Juan Sebastián Vega Patiño

gradient.py

@@ -1,18 +1,18 @@
 from __future__ import division
 from gaussian_filter import gaussian
-from numpy import array, zeros, abs, sqrt, arctan2
+from numpy import array, zeros, abs, sqrt, arctan2, pi
 from numpy.fft import fft2, ifft2
 from PIL import Image
 from matplotlib.pyplot import imshow, show, subplot, figure, gray, title, axis
 
 def gradient(im):
     # Sobel operator
     op1 = array([[-1, 0, 1],
-                 [-2, 0, 2],
-                 [-1, 0, 1]])
+     [-2, 0, 2],
+     [-1, 0, 1]])
     op2 = array([[-1, -2, -1],
-                 [0,   0,  0],
-                 [1,   2,  1]])
+     [0,   0,  0],
+     [1,   2,  1]])
     kernel1 = zeros(im.shape)
     kernel1[:op1.shape[0], :op1.shape[1]] = op1
     kernel1 = fft2(kernel1)
@@ -22,34 +22,34 @@ def gradient(im):
     kernel2 = fft2(kernel2)
 
     fim = fft2(im)
-    Gx = abs(ifft2(kernel1 * fim)).astype(float)
-    Gy = abs(ifft2(kernel2 * fim)).astype(float)
+    Gx = ifft2(kernel1 * fim).astype(float)
+    Gy = ifft2(kernel2 * fim).astype(float)
 
     G = sqrt(Gx**2 + Gy**2)
-    Theta = arctan2(Gy, Gx)
-
-    return G.astype(int), Theta.astype(int)
+    Theta = arctan2(Gy, Gx) * 180 / pi
+    return G, Theta
 
 if __name__ == '__main__':
-    im = array(Image.open("emilia.jpg"))
-    im = im[:, :, 0]
-    gim = gaussian(im)
-    grim, gphase = gradient(gim)
-    gray()
-
-    subplot(2, 2, 1)
-    imshow(im)
-    axis('off')
-    title('Original')
-
-    subplot(2, 2, 2)
-    imshow(gim)
-    axis('off')
-    title('Gaussian')
-
-    subplot(2, 2, 3)
-    imshow(grim)
-    axis('off')
-    title('Gradient')
-
-    show()
+  im = array(Image.open("emilia.jpg"))
+  im = im[:, :, 0]
+  gim = gaussian(im)
+  grim, gphase = gradient(gim)
+
+  gray()
+
+  subplot(2, 2, 1)
+  imshow(im)
+  axis('off')
+  title('Original')
+
+  subplot(2, 2, 2)
+  imshow(gim)
+  axis('off')
+  title('Gaussian')
+
+  subplot(2, 2, 3)
+  imshow(grim)
+  axis('off')
+  title('Gradient')
+
+  show()

nonmax_suppression.py

@@ -0,0 +1,63 @@
+from __future__ import division
+from gaussian_filter import gaussian
+from gradient import gradient
+from numpy import array, zeros
+from PIL import Image
+from matplotlib.pyplot import imshow, show, subplot, figure, gray, title, axis
+
+def maximum(det, phase):
+  gmax = zeros(det.shape)
+  for i in xrange(gmax.shape[0]):
+    for j in xrange(gmax.shape[1]):
+      if(phase[i][j] < 0):
+        phase[i][j] += 360
+
+      if( ((j+1) < gmax.shape[1]) and ((j-1) >= 0) and ((i+1) < gmax.shape[0]) and ((i-1) >= 0) ):
+        #0 grados
+        if((phase[i][j] >= 337.5 and phase[i][j] < 22.5) or (phase[i][j] >= 157.5 and phase[i][j] < 202.5)):
+          if(det[i][j] > det[i][j + 1] and det[i][j] > det[i][j - 1]):
+            gmax[i][j] = det[i][j]
+        #45 grados
+        if((phase[i][j] >= 22.5 and phase[i][j] < 67.5) or (phase[i][j] >= 202.5 and phase[i][j] < 247.5)):
+          if(det[i][j] > det[i - 1][j + 1] and det[i][j] > det[i + 1][j - 1]):
+            gmax[i][j] = det[i][j]
+        #90 grados
+        if((phase[i][j] >= 67.5 and phase[i][j] < 112.5) or (phase[i][j] >= 247.5 and phase[i][j] < 292.5)):
+          if(det[i][j] > det[i - 1][j] and det[i][j] > det[i + 1][j]):
+            gmax[i][j] = det[i][j]
+        #136 grados
+        if((phase[i][j] >= 112.5 and phase[i][j] < 157.5) or (phase[i][j] >= 292.5 and phase[i][j] < 337.5)):
+          if(det[i][j] > det[i - 1][j - 1] and det[i][j] > det[i + 1][j + 1]):
+            gmax[i][j] = det[i][j]
+  return gmax
+
+if __name__ == '__main__':
+  im = array(Image.open("emilia.jpg"))
+  im = im[:, :, 0]
+  gim = gaussian(im)
+  grim, gphase = gradient(gim)
+  gmax = maximum(grim, gphase)
+
+  gray()
+
+  subplot(2, 2, 1)
+  imshow(im)
+  axis('off')
+  title('Original')
+
+  subplot(2, 2, 2)
+  imshow(gim)
+  axis('off')
+  title('Gaussian')
+
+  subplot(2, 2, 3)
+  imshow(grim)
+  axis('off')
+  title('Gradient')
+
+  subplot(2, 2, 4)
+  imshow(gmax)
+  axis('off')
+  title('Non-Maximum suppression')
+
+  show()