If we know some properties of the image, than thresholding process only needs to ensure this property is satisfied. In a printed text image, if we know the ratio of area between the sheet and character, then we can choose satisfied threshold value

研究了Stein的估计和真实MSE的最小值之间的权衡，并把图像去噪问题看作联盟形成游戏。-studied the tradeoff between the accuracy of the Stein’s estimate and the minimum of the true MSE and formulated the image denoising problem as a coalition formation game.