针对灰度图像多层分割如何选取多目标图像分割的准确阈值这一难点问题，提出了一种利用三角级数来对直方图包络线进行拟合，首先把直方图包络线逼近问题转化为求解三角级数的问题，再通过计算拟合函数的拐点来得到用于多目标图像分割的最优阈值的方法。实验结果表明，该方法是求解多峰值直方图图像的最优分割阈值的有效手段。

It is difficult to obtain the accurate segmentation threshold for image. This paper uses the trigonometric series to approximate the histogram and analyzes the fitted curve of the histogram. The problem of the optimal threshold has been solved by estimating the parameters of the inflexion of the curve which approximated the histogram. The experimental result shows that this method is effective in calculating the optimal segmentation threshold of an image.