局部边缘保持滤波(LEP)高动态范围图像HDR压缩 matlab程序（一）

本文为转载，原博客地址为：http://blog.csdn.net/majinlei121/article/details/50420927

本文程序根据论文"Gu B, Li W, Zhu M, et al. Local edge-preserving multiscale decomposition for high dynamic range image tone mapping[J]. Image Processing, IEEE Transactions on, 2013, 22(1): 70-79."编写，主要为论文中提出的一种LEP局部边缘保持滤波程序，高动态图像压缩的程序在下一篇博客里。

下面为LEP函数程序：

 function out = LocalWls_HDR(I, alpha, beta, r)

 if ~exist('alpha','var')
     alpha = 0.1;
 end
 if ~exist('beta','var')
     beta = 1;
 end
 if ~exist('r','var')
     r = 4;
 end

 [hei, wid] = size(I);
 N = boxfilter(ones(hei, wid), r); % the size of each local patch; N=(2r+1)^2 except for boundary pixels.

 mean_I = boxfilter(I, r) ./ N;
 mean_II = boxfilter(I.*I, r) ./ N;

 var_I = mean_II - mean_I .* mean_I;

 I_x = diff(I,1,2);
 I_x = padarray(I_x, [0 1 0], 'post');%进行列方向差分，求dx
 I_y = diff(I,1,1);
 I_y = padarray(I_y, [1 0 0], 'post');%进行行方向差分，求dy
 I_gradient=abs(I_x+I_y);
 I_gradient=I_gradient.^(2-beta);
 I_gradient=alpha*boxfilter(I_gradient,r)./N;

 a = var_I ./ (var_I + I_gradient+0.00000001);
 b = mean_I - a .* mean_I;

 mean_a = boxfilter(a, r) ./ N;
 mean_b = boxfilter(b, r) ./ N;

 out = mean_a .* I + mean_b;
 end

其中用到的boxfilter()函数来自引导滤波，为：

 function imDst = boxfilter(imSrc, r)

 %   BOXFILTER   O(1) time box filtering using cumulative sum
 %
 %   - Definition imDst(x, y)=sum(sum(imSrc(x-r:x+r,y-r:y+r)));
 %   - Running time independent of r;
 %   - Equivalent to the function: colfilt(imSrc, [2*r+1, 2*r+1], 'sliding', @sum);
 %   - But much faster.

 [hei, wid] = size(imSrc);
 imDst = zeros(size(imSrc));

 %cumulative sum over Y axis
 imCum = cumsum(imSrc, 1);
 %difference over Y axis
 imDst(1:r+1, :) = imCum(1+r:2*r+1, :);
 imDst(r+2:hei-r, :) = imCum(2*r+2:hei, :) - imCum(1:hei-2*r-1, :);
 imDst(hei-r+1:hei, :) = repmat(imCum(hei, :), [r, 1]) - imCum(hei-2*r:hei-r-1, :);

 %cumulative sum over X axis
 imCum = cumsum(imDst, 2);
 %difference over X axis
 imDst(:, 1:r+1) = imCum(:, 1+r:2*r+1);
 imDst(:, r+2:wid-r) = imCum(:, 2*r+2:wid) - imCum(:, 1:wid-2*r-1);
 imDst(:, wid-r+1:wid) = repmat(imCum(:, wid), [1, r]) - imCum(:, wid-2*r:wid-r-1);
 end

运行程序为：

 clear all
 I = double(imread('..\images\stripes.png')) / 255;

 alpha=0.1;
 beta=1;
 r=2;

 out = LocalWls_HDR(I, alpha, beta, r);

 figure();imshow([I, out], [0, 1]);title('input,LEP');
 row=155;
 figure;plot(1:size(I,2), I(row,:,1),1:size(I,2), out(row,:,1), 'LineWidth', 2);
 legend('input','LEP');

效果图为：