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OpenCV中圖像頻率域濾波(傅里葉變換 + 高通/低通 濾波)[python] 資料來源: https://mp.weixin.qq.com/s/w2D2q5Ym7HnPWPP7VOWjJw CV API 原型 # 傅里叶变换函数 void cv::dft( InputArray src, OutputArray dst, int flags = 0, int nonzeroRows = 0 ) # 傅里叶逆变换函数 void cv::idft( InputArray src, OutputArray dst, int flags = 0, int nonzeroRows = 0 ) 低通 def low_pass_filter_demo(): image = cv.imread("D:/images/test1.png", cv.IMREAD_GRAYSCALE) img_float32 = np.float32(image) rows, cols = image.shape crow, ccol = rows//2 , cols//2 # FFT变换 dft = cv.dft(img_float32, flags = cv.DFT_COMPLEX_OUTPUT) dft_shift = np.fft.fftshift(dft) # 创建低通滤波器，低频区域为 1， 高频区域为 0 mask = np.zeros((rows, cols, 2), np.uint8) mask[crow-30:crow+30, ccol-30:ccol+30] = 1 # 滤波 fshift = dft_shift*mask # 逆变换 f_ishift = np.fft.ifftshift(fshift) img_back = cv.idft(f_ishift) img_back = cv.magnitude(img_back[:,:,0],img_back[:,:,1]) cv.normalize(img_back, img_back, 0, 1.0, cv.NORM_MINMAX) cv.imshow("input", image); cv.imshow("low-pass-filter", img_back) cv.imwrite("D:/low_pass.png", np.uint8(img_back*255)) cv.waitKey(0) cv.destroyAllWindows() 高通 def high_pass_filter_demo(): image = cv.imread("D:/images/test1.png", cv.IMREAD_GRAYSCALE) img_float32 = np.float32(image) rows, cols = image.shape crow, ccol = rows//2 , cols//2 # FFT变换 dft = cv.dft(img_float32, flags = cv.DFT_COMPLEX_OUTPUT) dft_shift = np.fft.fftshift(dft) # 创建高通滤波器，低频区域为 0， 高频区域为 1 mask = np.ones((rows, cols, 2), np.uint8) mask[crow-30:crow+30, ccol-30:ccol+30] = 0 # 滤波 fshift = dft_shift*mask # 逆变换 f_ishift = np.fft.ifftshift(fshift) img_back = cv.idft(f_ishift) img_back = cv.magnitude(img_back[:,:,0],img_back[:,:,1]) cv.normalize(img_back, img_back, 0, 1.0, cv.NORM_MINMAX) cv.imshow("input", image); cv.imshow("high-pass-filter", img_back) cv.imwrite("D:/high_pass.png", np.uint8(img_back*255)) cv.waitKey(0) cv.destroyAllWindows()