chan-vese模型
Python--level set （水平集）和 chan-vese模型
2018年08月28日 10:51:54 GlassySky0816 阅读数：1604
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level set :https://www.zhihu.com/question/22608763?sort=created
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chan-vese模型(公式推导）：<>
水平集（CV模型）代码：
import cv2
from pylab import*
Image = cv2.imread( '02.jpg', 1) # 读入原图
image = cv2.cvtColor(Image, cv2.COLOR_BGR2GRAY)
img = np.array(image, dtype=np.float64) # 读入到np的array中，并转化浮点类型
初始水平集函数
IniLSF = np.ones((img.shape[ 0], img.shape[1]), img.dtype)
IniLSF[ 300:320, 300:320] = -1
IniLSF = -IniLSF
画初始轮廓
Image = cv2.cvtColor(Image, cv2.COLOR_BGR2RGB)
创建图像窗口，并使用imshow函数显示图片Image；随后分别隐藏x轴和y轴的刻度标签
plt.contour(IniLSF, [ 0], color='b', linewidth=2) # 画LSF=0处的等高线
plt.draw(), plt.show(block= False)
def mat_math(intput, str):
output = intput
for i in range(img.shape[0]):
for j in range(img.shape[1]):
if str == "atan":
output[i, j] = math.atan(intput[i, j])
if str == "sqrt":
output[i, j] = math.sqrt(intput[i, j])
return output
CV函数
def CV(LSF, img, mu, nu, epison, step):
Drc = (epison / math.pi) / (episonepison + LSFLSF)
Hea = 0.5*(1 + (2 / math.pi)*mat_math(LSF/epison, "atan"))
Iy, Ix = np.gradient(LSF)
s = mat_math(IxIx+IyIy, "sqrt")
Nx = Ix / (s+ 0.000001)
Ny = Iy / (s+ 0.000001)
Mxx, Nxx = np.gradient(Nx)
Nyy, Myy = np.gradient(Ny)
cur = Nxx + Nyy
Length = nuDrccur
Lap = cv2.Laplacian(LSF, -1)
Penalty = mu*(Lap - cur)
s1 = Hea*img
s2 = ( 1-Hea)*img
s3 = 1-Hea
C1 = s1.sum() / Hea.sum()
C2 = s2.sum() / s3.sum()
CVterm = Drc*( -1 * (img - C1)(img - C1) + 1 * (img - C2)(img - C2))
LSF = LSF + step*(Length + Penalty + CVterm)
plt.imshow(s, cmap ='gray'),plt.show()
return LSF
模型参数
mu = 1
nu = 0.003 * 255
num = 20
epison = 1
step = 0.1
LSF = IniLSF
for i in range(1, num):
LSF = CV(LSF, img, mu, nu, epison, step) # 迭代
if i % 1 == 0: # 显示分割轮廓
plt.imshow(Image), plt.xticks([]), plt.yticks([])
plt.contour(LSF, [ 0], colors='r', linewidth=2)
plt.draw(), plt.show(block= False), plt.pause(0.01)
为什么上传图片这么麻烦。
一、文章参考
Chan T F and Vese L. The paper titled "Active contours without edges" was published in the IEEE Transactions on Image Processing in 2001.
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作者：jonson_zc
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