preprocess.py 文件源码

def calcDirection(img,blockSize):
    """calculate ridge directions in an image, using gradient method
    return: ridge directions
    """
    sobel_x=np.array([[1, 0, -1],[2, 0, -2],[1, 0, -1]])
    sobel_y=np.array([[1, 2, 1],[0, 0, 0],[-1,-2,-1]])
    par_x=convolve2d(img,sobel_x,mode='same')
    par_y=convolve2d(img,sobel_y,mode='same')
    N,M=np.shape(img)
    Vx=np.zeros((N/blockSize,M/blockSize))
    Vy=np.zeros((N/blockSize,M/blockSize))
    for i in xrange(N/blockSize):
        for j in xrange(M/blockSize):
            a=i*blockSize;b=a+blockSize;c=j*blockSize;d=c+blockSize
            Vy[i,j]=2*np.sum(par_x[a:b,c:d]*par_y[a:b,c:d])
            Vx[i,j]=np.sum(par_y[a:b,c:d]**2-par_x[a:b,c:d]**2)
    gaussianBlurSigma=2;    gaussian_block=5
    Vy=cv2.GaussianBlur(Vy,(gaussian_block,gaussian_block),gaussianBlurSigma,gaussianBlurSigma)
    Vx=cv2.GaussianBlur(Vx,(gaussian_block,gaussian_block),gaussianBlurSigma,gaussianBlurSigma)
    theta=0.5*np.arctan2(Vy,Vx)            
    return theta