python去噪算法
2024-10-02 01:56:07
《programming computer vision with python 》中denoise 算法有误,从网上好了可用的代码贴上,以便以后使用。
书中错误的代码:
def denoise(im,U_init,tolerance=0.1,tau=0.125,tv_weight=100):
m,n = im.shape
U = U_init
Px = im
Py = im
error = 1 while (error > tolerance):
Uold = U
GradUx = roll(U,-1,axis=1)-U
GradUy = roll(U,-1,axis=0)-U PxNew = Px + (tau/tv_weight)*GradUx
PyNew = Py + (tau/tv_weight)*GradUy
NormNew = maximum(1,sqrt(PxNew**2+PyNew**2)) Px = PxNew/NormNew
py = PyNew/NormNew RxPx = roll(Px,1,axis=1)
RyPy = roll(Py,1,axis=0) DivP = (Px - RxPx) + (Py - RyPy)
U = im + tv_weight*DivP error = linalg.norm(U-Uold)/sqrt(n*m)
return U,im-U
网上可用的代码:
def denoise(im, U_init, tolerance=0.1, tau=0.125, tv_weight=100):
""" An implementation of the Rudin-Osher-Fatemi (ROF) denoising model
using the numerical procedure presented in Eq. (11) of A. Chambolle
(2005). Implemented using periodic boundary conditions
(essentially turning the rectangular image domain into a torus!). Input:
im - noisy input image (grayscale)
U_init - initial guess for U
tv_weight - weight of the TV-regularizing term
tau - steplength in the Chambolle algorithm
tolerance - tolerance for determining the stop criterion Output:
U - denoised and detextured image (also the primal variable)
T - texture residual""" #---Initialization
m,n = im.shape #size of noisy image U = U_init
Px = im #x-component to the dual field
Py = im #y-component of the dual field
error = 1
iteration = 0 #---Main iteration
while (error > tolerance):
Uold = U #Gradient of primal variable
LyU = vstack((U[1:,:],U[0,:])) #Left translation w.r.t. the y-direction
LxU = hstack((U[:,1:],U.take([0],axis=1))) #Left translation w.r.t. the x-direction GradUx = LxU-U #x-component of U's gradient
GradUy = LyU-U #y-component of U's gradient #First we update the dual varible
PxNew = Px + (tau/tv_weight)*GradUx #Non-normalized update of x-component (dual)
PyNew = Py + (tau/tv_weight)*GradUy #Non-normalized update of y-component (dual)
NormNew = maximum(1,sqrt(PxNew**2+PyNew**2)) Px = PxNew/NormNew #Update of x-component (dual)
Py = PyNew/NormNew #Update of y-component (dual) #Then we update the primal variable
RxPx =hstack((Px.take([-1],axis=1),Px[:,0:-1])) #Right x-translation of x-component
RyPy = vstack((Py[-1,:],Py[0:-1,:])) #Right y-translation of y-component
DivP = (Px-RxPx)+(Py-RyPy) #Divergence of the dual field.
U = im + tv_weight*DivP #Update of the primal variable #Update of error-measure
error = linalg.norm(U-Uold)/sqrt(n*m);
iteration += 1; print iteration, error #The texture residual
T = im - U
print 'Number of ROF iterations: ', iteration return U,T
测试代码:
from numpy import *
from numpy import random
from scipy.ndimage import filters
import rof
from scipy.misc import imsave im = zeros((500,500))
im[100:400,100:400] = 128
im[200:300,200:300] = 255 im = im + 30*random.standard_normal((500,500)) imsave('synth_ori.pdf',im) U,T = rof.denoise(im,im,0.07) G = filters.gaussian_filter(im,10) imsave('synth_rof.pdf',U)
imsave('synth_gaussian.pdf',G)
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