Research On Brightness Compensation Algorithm Of Gaofen-3 SAR Image

The uneven light phenomenon of remote sensing image referred to the uneven distribution of brightness and contrast in remote sensing image.Among them,Synthetic Aperture Radar(SAR)image belongs to one kind of remote sensing image.With the continuous development and progress of Space-borne SAR system in China,,its image data plays a more and more important role in national economic construction and military reconnaissance.GF-3,the first C-Band full-polarimetric synthetic aperture radar satellite with a space resolution up to 1m,has multiple strip and scan imaging modes.With the continuous and stable operation of GF-3 satellite in orbit,the massive SAR image data have been studied more and more deeply.When we are using GF-3 data,the SAR image brightness is required to be balanced,the contrast is moderate,and the color is consistent.However,because SAR is a microwave slant-range imaging radar,the quality of SAR image will be affected by radar polarization,radar wavelength,radar lateral angle of view,ground texture characteristics and other factors during the imaging process,which makes the SAR amplitude image have a larger dynamic range,The phenomenon of uneven brightness and inconsistent contrast will appear,which requires timely image processing,there will be appearing uneven brightness and inconsistent contrast phenomenon,so that we need to process the image in time.Brightness compensation is an important part of remote sensing image processing.It can correct the phenomenon of uneven brightness and inconsistent contrast,and improve image quality and visual effect.In this paper,we aim at GF-3 SAR image with unbalanced radiation in some areas,we propose corresponding brightness compensation method by analyzing the advantages and disadvantages of existing brightness compensation algorithms.The main innovations and research work are as follows:(1)Through the analysis of the image radiation imbalance phenomenon,a brightness compensation model is proposed to correct the unbalanced radiation image of GF-3 satellite in some areas based on mathematical morphology principle,SAR imaging model,and histogram mapping model,we correct the SAR image according to the process of denoise,brightness compensation and gray enhancement.Firstly,we use the top-hat transform to reduce the bright target in the image;and then,we use the SAR imaging model to further compensate the brightness of the image block;finally,we choose the image with moderate contrast and no radiation difference as the reference image,and use histogram mapping method to enhance the image.(2)In this paper,four evaluation indexes of brightness mean,standard deviation,information entropy and average gradient are used to evaluate and analyze the image of the experiment part.(3)In this paper,the proposed algorithm is step-by-step tested and evaluated on the GF-3 SAR image with radiation difference in Taklimakan desert area of Xinjiang,and compared with the MASK dodging algorithm and Wallis filter algorithm.Results of brightness compensation show that,the proposed algorithm makes the radiation differences within images smaller,and the image quality is obviously improved,which provides a non-radiation difference image for subsequent applications.