A correct method based on retinex for the solar image with uneven illumination

The traditional mask method and background fitting method can not correct effectively the solar image with uneven illumination. We adopt a correct method based on Retinex for the solar image with uneven illumination. The quality of image is improved by compressing the range of brightness and increasing the contrast by separately processing the effect of illumination and reflectivity to the intensity value. It could reveal the detailed character of the shadow area of the image. By contrasting four evaluate indexes, including the mean intensity, the image entropy, the image contrast and the peak signal to noise ratio (PSNR), this method is proved to be effective in the solar image with uneven illumination.