function ret_im = Gamma_MAP( im, w_size, out_size, NL, bound, flag)%GAMMA_MAP Gamma-MAP filter for SAR speckle reduction%   im：SAR影像%   w_size：窗口大小，奇數 3 5 7 9等%   out_size：輸出圖像的大小，可以是'same'或者'full'%   NL：number of Looks，等效視數%   bound：邊緣擴展模式，分為'symmetric'，'replicate','circular'。%   flag：計算時是否包含中心像素，0為不包含，1為包含。%%   ret_im：濾波結果影像%% barbara_gammaMAP = Gamma_MAP( barbara_noisy, 5, 'same', 3, 'symmetric', 0);im = double(im);[im_Mean, im_Var] = im_mean_var(im, w_size, out_size, bound, flag);im_Std = sqrt(im_Var);Cu = sqrt(1/NL);Cmax = sqrt(2)*Cu;Ci = im_Std ./ im_Mean;A = (1+Cu^2) ./ (Ci .^2 - Cu^2);B = A - NL - 1;D = im_Mean.^2 .* B.^2 + 4.*A.*NL.*im_Mean.*im;Rf = (B.*im_Mean + sqrt(D)) ./ (2.*A);tmp1 = (Ci<=Cu);tmp1 = tmp1 .* im_Mean;tmp2 = (Ci>Cu & Ci<Cmax);tmp2 = tmp2 .* Rf;tmp3 = (Ci >= Cmax);tmp3 = tmp3 .* im;ret_im = tmp1+tmp2+tmp3;