Coffee beans separation algorithm

Question

What is proper algorithm for separating (counting) coffee beans on binary image? Beans can touch and partially overlap.

_{(source: beucher at cmm.ensmp.fr)}

Answer 1

Here is some code (in Python) that will give you a baseline. Count the number of black pixels and divide into the area accounting by how many circles of average size can be packed into a square of your size. The has the virtue of being the simplest possible thing you can do.

If a given method is not on average more accurate than this, then you need a better method. BTW I'm getting around 85% accuracy, so your 95% is not out of the question.

import Image

im = Image.open('ex2a.gif').convert('RGB')
(h,w) = im.size
print h,w
num_pixels = h*w
print num_pixels
black_pixels = 0
for i in range(h):
    for j in range(w):
        q = im.getpixel((i,j)) 
        if q[0]<10 and q[1]<10 and q[2]<10:
            black_pixels = black_pixels + 1
            im.putpixel((i,j),(255,0,0))
r = 15
unpackable = (h/(2*r))*(w/(2*r))*((2*r)**2 - 3.14*r**2)
print 'unpackable:',unpackable
print 'num beans:',round((num_pixels-2*unpackable)/750.0)
im.save('qq.jpg')