dsift.py 文件源码

def calculate_sift_grid(self, image, rangeH, rangeW):
        H, W = image.shape
        feat = np.zeros((len(rangeH), len(rangeW), self.Nsamples*self.Nangles))
        IH = filters.convolve(image, self.GH, mode='nearest')
        IW = filters.convolve(image, self.GW, mode='nearest')
        I_mag = np.sqrt(IH ** 2 + IW ** 2)
        I_theta = np.arctan2(IH, IW)
        I_orient = np.empty((H, W, self.Nangles))
        for i in range(self.Nangles):
            I_orient[:,:,i] = I_mag * np.maximum(
                    np.cos(I_theta - self.angles[i]) ** self.alpha, 0)
        for i, hs in enumerate(rangeH):
            for j, ws in enumerate(rangeW):
                feat[i, j] = np.dot(self.weights,
                                    I_orient[hs:hs+self.pS, ws:ws+self.pS]\
                                        .reshape(self.pS**2, self.Nangles)
                                   ).flat
        return feat