First,it takes an iterative partial threshold to determine the threshold of each sub-image.

Aiming at problems in current study of sonar image enhancement,a new enhancement method based iterative threshold was presented,the criterion function and frequency response were used to evaluate and compare current image enhancement arithmeti.

A modification to Linearly Decreasing Weight strategy in standard Particle Swarm Optimization is taken by introducing descending index and iterative threshold.

The identification card scanned image is seriously affected by laser restraining false shadow grid, several binarization methods of document image are studied according to this characteristic, an image binarization method is proposed , which is called iterative threshold methodbased on the neighborhood feature of the pixels .

In order to restore the binary image information from the gray character image with noise and distortion through the filtering method, an adaptive binarization filtering algorithm is put forward based on the combination of adaptive filtering with local threshold binarization.

Based on operators for edge feature detection, a new method of adaptive threshold selection is proposed which combines the local threshold with global threshold selection.

They are improved bayesian image denoising based on wavelets,image denoising based on lifting wavelet and subbands adaptive threshold,wavelet image denoising base on local threshold.