Currently

related image quality assessment methods can not appropriately measure structure-preserving capability of synthetic aperture radar (SAR) image despeckling

to solve this problem a no-reference improved equivalent number of looks of ratio image(IENLR) assessment method is put forward. To begin with

related image quality assessment methods are reviewed

where their weaknesses to measure structure-preserving capability are investigated. Furthermore

from equivalent number of looks of ratio(ENLR) image as a point of departure

the computing formula of IENLR is constructed

meanwhile theory analyses prove that IENLR is a basically monotone

bounded function with regard to structure-preserving capability

and that IENLR is adjustable in the light of its parameter. Finally

simulated experiments further verify that IENLR is excellent and superior to other related image quality assessment methods from the viewpoint of measuring structure-preserving capability.