Almost the existing image enhancement algorithms are not capable to deal with multi-type degenerated images.In this paper

a fast image enhancement algorithm is proposed based on prior knowledge and atmospheric scattering model.Firstly

an innovative image prior

which were called bright channel prior

were proposed through experimental statistics.It shows that the whites spots are more likely to exist in the neighborhood of each pixels in high-quality clear image.Then

the scattering model were improved and it derived the calculation formula of reflectance image by bright channel prior

dark channel prior and improved scattering model.Finally

we put forward a fault tolerance mechanism

which is based on reliability prediction

to handle the situation that the dark channel prior does not work.The experiment results shows that this algorithm can not only highlight the texture details well but also restore the tone.It is able to deal with multi-type degenerated images.