fourierDescriptor.py

#!/usr/bin/env python
# -*-coding:utf-8 -*-
import cv2
import numpy as np

MIN_DESCRIPTOR = 32  # surprisingly enough, 2 descriptors are already enough

##计算傅里叶描述子
def fourierDesciptor(res):
    #Laplacian算子进行八邻域检测
    gray = cv2.cvtColor(res, cv2.COLOR_BGR2GRAY)
    dst = cv2.Laplacian(gray, cv2.CV_16S, ksize = 3)
    Laplacian = cv2.convertScaleAbs(dst)
    contour = find_contours(Laplacian)#提取轮廓点坐标
    contour_array = contour[0][:, 0, :]#注意这里只保留区域面积最大的轮廓点坐标
    ret_np = np.ones(dst.shape, np.uint8) #创建黑色幕布
    ret = cv2.drawContours(ret_np,contour[0],-1,(255,255,255),1) #绘制白色轮廓
    contours_complex = np.empty(contour_array.shape[:-1], dtype=complex)
    contours_complex.real = contour_array[:,0]#横坐标作为实数部分
    contours_complex.imag = contour_array[:,1]#纵坐标作为虚数部分
    fourier_result = np.fft.fft(contours_complex)#进行傅里叶变换
    #fourier_result = np.fft.fftshift(fourier_result)
    descirptor_in_use = truncate_descriptor(fourier_result)#截短傅里叶描述子
    #reconstruct(ret, descirptor_in_use)
    return ret, descirptor_in_use

def find_contours(Laplacian):
    #binaryimg = cv2.Canny(res, 50, 200) #二值化，canny检测
    h = cv2.findContours(Laplacian,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE) #寻找轮廓
    contour = h[1]
    contour = sorted(contour, key = cv2.contourArea, reverse=True)#对一系列轮廓点坐标按它们围成的区域面积进行排序
    return contour

#截短傅里叶描述子
def truncate_descriptor(fourier_result):
    descriptors_in_use = np.fft.fftshift(fourier_result)

    #取中间的MIN_DESCRIPTOR项描述子
    center_index = int(len(descriptors_in_use) / 2)
    low, high = center_index - int(MIN_DESCRIPTOR / 2), center_index + int(MIN_DESCRIPTOR / 2)
    descriptors_in_use = descriptors_in_use[low:high]

    descriptors_in_use = np.fft.ifftshift(descriptors_in_use)
    return descriptors_in_use

##由傅里叶描述子重建轮廓图
def reconstruct(img, descirptor_in_use):
    #descirptor_in_use = truncate_descriptor(fourier_result, degree)
    #descirptor_in_use = np.fft.ifftshift(fourier_result)
    #descirptor_in_use = truncate_descriptor(fourier_result)
    #print(descirptor_in_use)
    contour_reconstruct = np.fft.ifft(descirptor_in_use)
    contour_reconstruct = np.array([contour_reconstruct.real,
                                    contour_reconstruct.imag])
    contour_reconstruct = np.transpose(contour_reconstruct)
    contour_reconstruct = np.expand_dims(contour_reconstruct, axis = 1)
    if contour_reconstruct.min() < 0:
        contour_reconstruct -= contour_reconstruct.min()
    contour_reconstruct *= img.shape[0] / contour_reconstruct.max()
    contour_reconstruct = contour_reconstruct.astype(np.int32, copy = False)

    black_np = np.ones(img.shape, np.uint8) #创建黑色幕布
    black = cv2.drawContours(black_np,contour_reconstruct,-1,(255,255,255),1) #绘制白色轮廓
    cv2.imshow("contour_reconstruct", black)
    #cv2.imwrite('recover.png',black)
    return black


####测试####
'''
cnt = 1
path = './image_example/' + str(cnt) + '.png'
img = cv2.imread(path)
efds, K_array, T_array = elliptic_fourier_descriptors(img, 20)
contour_reconstruct = reconstruct_efd(efds[:], T_array[1], K_array[1])
contour_reconstruct = contour_reconstruct.astype(np.int32, copy = False)
black = np.ones(img.shape, np.uint8) #创建黑色幕布
cv2.drawContours(black,contour_reconstruct,-1,(255,255,255),1) #绘制白色轮廓
cv2.imshow("contour_reconstruct", black)
cv2.imwrite("1_copy,png", black)
cv2.waitKey(1000)
'''