Adds simple histogram calculation.

Support for 3 channel / diverse encoding image should be added soon. 

Other functions to be integrated: 
-histogram to numpy table
-histogram image creation

Signed-off-by: Julien Lengrand-Lambert <julien@lengrand.fr>

tippy/statistics.py

@@ -0,0 +1,63 @@
+'''
+Contains functions related to statistics processing. 
+
+Created on Dec 11, 2011
+
+@author: Julien Lengrand-Lambert
+@email: julien@lengrand.fr
+'''
+
+import cv
+import sys
+
+def compute_histogram(img, bin_fact=cv.IPL_DEPTH_8U, min_range=0):
+    """
+    This function is designed to create the color histogram of the image in 
+    input.
+    Returns a list of histograms, with one item by channel of input image.
+    The number of bins is 2^bin_fact (256 by default)
+    min_range is the lowest bin taken. max_range is automatically calculated with 
+    the input image depth. (2^img_depth)
+    
+    NOTE : Supports only 1 channel / 8 bits images for now. 
+    More should be added soon.
+    """
+    try:
+        cv.GetSize(img)
+    except TypeError:
+        raise TypeError("(%s) img : IplImage expected!" % (sys._getframe().f_code.co_name))
+    
+    # img test
+    if not(img.depth == cv.IPL_DEPTH_8U):
+        raise TypeError("(%s) 8U image expected!" % (sys._getframe().f_code.co_name))
+    elif not(img.nChannels is 1):
+        raise TypeError("(%s) 1C image expected!" % (sys._getframe().f_code.co_name))
+    
+    # bin_fact test
+    if (bin_fact <= 0 or ((bin_fact % 2) != 0)):
+        raise ValueError("(%s) Positive odd integer expected!" % (sys._getframe().f_code.co_name))
+    elif type(bin_fact) != int:
+        raise TypeError("(%s) Positive odd integer expected!" % (sys._getframe().f_code.co_name))
+
+    # min_range test
+    if type(min_range) != int:
+        raise TypeError("(%s) Positive odd integer expected!" % (sys._getframe().f_code.co_name))    
+    
+    bins = pow(2, bin_fact)
+    max_range = pow(2, img.depth)
+    ranges = [min_range, max_range]
+
+    dims = [bins]
+    all_ranges = [ranges]
+    
+    hist = cv.CreateHist( dims, cv.CV_HIST_ARRAY, all_ranges, uniform=1)
+    cv.CalcHist([img], hist)
+
+    return hist
+
+def hist2table(hist):
+    """
+    Transform an histogram into a (numpy) table of values.
+    This way, it is easier to process.    
+    """
+    pass

tippy/tests/test_statistics.py

@@ -0,0 +1,50 @@
+'''
+Created on Dec 11, 2011
+
+@author: Julien Lengrand-Lambert
+@email: julien@lengrand.fr
+'''
+import unittest
+import cv
+
+import tippy.statistics as st
+
+class Test(unittest.TestCase):
+
+
+    def setUp(self):
+        """
+        This method is called before each test
+        """
+        self.img_1c = cv.LoadImage("data/tippy.jpg", cv.CV_LOAD_IMAGE_GRAYSCALE) # 1 channel image 
+        self.img_3c = cv.LoadImage("data/tippy.jpg", cv.CV_LOAD_IMAGE_COLOR) # 3 channel image 
+        self.img_16s = cv.CreateImage((15, 15), cv.IPL_DEPTH_16S, 1) # Non 8 bits image
+        
+        self.val = 10 # non Image
+        self.neg_val = -10 # non Image
+        self.string = "A" # non Image
+
+    def tearDown(self):
+        """
+        This method is called after each test
+        """
+        pass
+
+    #--- 
+    ## TESTS
+    def test_compute_histogram(self):
+        # testing input image
+        # st.compute_histogram(self.img_1c)
+        self.assertRaises(TypeError, lambda: st.compute_histogram(self.val) )
+        self.assertRaises(TypeError, lambda: st.compute_histogram(self.img_3c) )        
+        
+        # testing bin_fact
+        self.assertRaises(ValueError, lambda: st.compute_histogram(self.img_1c, self.neg_val) )
+        self.assertRaises(TypeError, lambda: st.compute_histogram(self.img_1c, self.string) ) 
+
+        # testing min_range. It can be either negative or even.
+        self.assertRaises(TypeError, lambda: st.compute_histogram(self.img_1c, self.val, self.string) ) 
+
+#if __name__ == "__main__":
+    #import sys;sys.argv = ['', 'Test.testName']
+    #unittest.main()