'''
Created on 14 avr. 2014

@author: vialard
'''
import numpy as np
import matplotlib.cm as cm

def GoldenSearch(func,x,gradient,tol):
    alpha= (np.sqrt(5)-1)/2;
    a = 0.
    b= 0.5
    iter = 0
    #print "######## Golden start #########"
    while (func(x-gradient*a)<=func(x-gradient*b) and (iter<10)):
        b/=2.
        iter+=1

    c = 2*b
    iter = 0
    while np.abs(b-a)>tol:
        c = alpha*a + (1-alpha)*b
        d= a+b-c
        if func(x-gradient*c)<func(x-gradient*d):
            b=d
        else:
            a=c 
        iter +=1

    print "golden search iterations: ",iter  
    #print x-gradient*a
    #print "######## Golden end #########"
    return (a+b)*0.5



def GenereMasque(shape,niveau):
    mask = (np.random.randn(*shape))
    ArrangeMask(mask,shape)
    ArrangeMask(mask,shape)
    ArrangeMask(mask,shape)
    return (mask>niveau)

def ArrangeMask(mask,shape):   
    nx = shape[0]
    ny = shape[1]
    mask[1:nx,:] += mask[1:nx,:]
    mask[0:nx-1,:] += mask[1:nx,:]
    mask/=3.0
    mask[:,1:ny]+= mask[:,0:ny-1]
    mask[:,0:ny-1]+= mask[:,1:ny]
    mask/=3.0
    
if __name__ == "__main__":
    mask = GenereMasque((512,512),1.9)
    import pylab as pl
    pl.imshow(mask, cmap = cm.Greys_r)
    pl.show()