Programs related to convolution are added

* .gitignore: Ignore .DS_Store file generated by Mac's Finder
* conv.py: Created. It convolves a picture and show the comparison
	between the old picture and the convolved one.
* edge_detect.py: Using sobel operator, this program is able to detect all
	the edges of a picture
* invert.py: A simple program that inverts the color of a picture
* lena.png: Universal sample picture for image recognition
* sketch.py: This program both detects the edges in the pictures and
	invert the colors of the result in order to make it look like
	a sketch of this picture
* track.py: Remove useless variables

.gitignore

@@ -1 +1,2 @@
+.DS_Store
 *.face

conv.py

@@ -0,0 +1,15 @@
+#!/usr/bin/env python3
+import cv2
+import numpy as np
+
+img=cv2.imread("lena.png",cv2.IMREAD_COLOR)
+kernel=np.array([
+    [-1,0,1],
+    [-2,0,2],
+    [-1,0,1]
+],np.float32)
+print(kernel)
+result=cv2.filter2D(img,-1,kernel)
+merged=np.hstack([img,result])
+cv2.imshow("Lena",merged)
+cv2.waitKey(0)

edge_detect.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+import cv2
+import numpy as np
+import sys
+import os
+
+argc=len(sys.argv)
+if argc<2:
+    print("usage: %s image_file" % sys.argv[0])
+    exit(1)
+
+if os.path.exists(sys.argv[1])==False:
+    print("%s does not exist" % sys.argv[1])
+    exit(-1)
+
+# Output file name
+output_name="%s_sobel.png" % os.path.splitext(sys.argv[1])[0]
+
+# Detect edges using sobel operator
+sobel_x=np.array([
+    [-1,0,1],
+    [-2,0,2],
+    [-1,0,1]
+])
+
+sobel_y=np.array([
+    [1,2,1],
+    [0,0,0],
+    [-1,-2,-1]
+])
+
+img=cv2.imread(sys.argv[1],cv2.IMREAD_GRAYSCALE)
+result_x=cv2.filter2D(img,-1,sobel_x)
+result_y=cv2.filter2D(img,-1,sobel_y)
+result=result_x+result_y
+
+cv2.imwrite(output_name,result)

invert.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+import sys
+
+argc=len(sys.argv)
+if argc<2:
+    print("usage: %s image_file" % sys.argv[0])
+    exit(1)
+
+import os
+if os.path.exists(sys.argv[1])==False:
+    print("%s does not exist" % sys.argv[1])
+    exit(-1)
+
+out_name="%s_inverted.png" % os.path.splitext(sys.argv[1])[0]
+
+import cv2
+import numpy as np
+
+img=cv2.imread(sys.argv[1],cv2.IMREAD_COLOR)
+img2=np.zeros_like(img)
+
+for i,row in enumerate(img):
+    for j,col in enumerate(row):
+        img2[i,j]=0xFF-col
+
+cv2.imwrite(out_name,img2)

sketch.py

@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+
+# Default high contrast level
+level=5
+
+if __name__=="__main__":
+    import sys
+
+    argc=len(sys.argv)
+    if argc<2:
+        print("usage: %s image_file" % sys.argv[0])
+        exit(1)
+
+    import os
+
+    if os.path.exists(sys.argv[1])==False:
+        print("%s does not exist" % sys.argv[1])
+        exit(-1)
+
+    out_name="%s_sketch.png" % os.path.splitext(sys.argv[1])[0]
+
+import numpy as np
+import cv2
+
+sobel_x=np.array([
+    [-1,0,1],
+    [-2,0,2],
+    [-1,0,1]
+])
+
+sobel_y=np.array([
+    [1,2,1],
+    [0,0,0],
+    [-1,-2,-1]
+])
+
+# This function helps make higher contrast of colors
+# NOTE: The variable x must be normalized previously!
+def f(x):
+    return 1/(1+np.exp(-level*(x-0.5)))
+
+def make_sketch(img):
+    result_x=cv2.filter2D(img,-1,sobel_x)
+    result=cv2.filter2D(img,-1,sobel_y)
+    result+=result_x
+    # Now invert the image
+    proceeded=np.zeros_like(result)
+    for i,row in enumerate(result):
+        for j,col in enumerate(row):
+            normalized=(0xFF-col)/0xFF
+            proceeded[i][j]=int(f(normalized)*0xFF)
+    return proceeded
+
+if __name__=="__main__":
+    img=cv2.imread(sys.argv[1],cv2.IMREAD_GRAYSCALE)
+    final=make_sketch(img)
+    # Now save the output
+    cv2.imwrite(out_name,final)

track.py

@@ -37,10 +37,6 @@
 
 tracker=None
 
-# Used by mouse_handler() and tracking
-flag=False
-drawing=False
-
 # Stores current frame
 frame=None