圖像增強序列——Adaptive Local Power-Law Transformation for Color Image Enhancement(自適應伽馬變換)

1. 參考文獻

2. 模型實現

% 論文： Adaptive Local Power-Law Transformation for Color Image Enhancement
% 作者： Chun-Ming Tsai
%
% Author: HSW
% Date: 2018-04-27

clc;
close all;
clear;

img = imread('timg2.jpg');

figure(1);
imshow(img, []);
title('原圖像');

if size(img, 3) == 3
    img_hsv = rgb2hsv(img);
    img_V = img_hsv(:, :, 3);
    img_V  = img_V .* 255;
    img_V_out = img_V;
    alpha = 2.2;
    [m, n] = size(img_V);
    hsize = 3;
    totalPixel = (2*hsize + 1) * (2*hsize + 1);
    method = 2; % = 1 表示普通的計算方法， = 2 表示利用積分圖的計算方法
    
    if method == 1
        t0_1 = tic;
        for i = hsize + 1:m - hsize
            for j = hsize + 1:n - hsize
                mu = sum(sum(img_V(i + [-hsize:hsize], j + [-hsize:hsize]))) / totalPixel;
                gama = ( 1 / alpha)^((128 - mu) / 128.0);
                img_V_out(i, j) = uint8(255 * (img_V(i,j) / 255.0)^gama);
            end
        end
        t0_2 = toc(t0_1);
        disp(num2str(t0_2));
    else   
        img_v_int = boxFilter(img_V); % 計算積分圖花費的時間比較多，但是，對於矩形窗口較大的場景是有利的，感興趣的可以自己測試
        t1_1 = tic;
        for i = hsize+1:m-hsize
            for j = hsize+1:n-hsize
                mu = (img_v_int(i + hsize, j + hsize) + img_v_int(i - hsize, j - hsize) - img_v_int(i + hsize, j - hsize) - img_v_int(i - hsize, j + hsize)) / totalPixel;
                gama = ( 1 / alpha)^((128 - mu) / 128.0);
                img_V_out(i, j) = uint8(255 * (img_V(i,j) / 255.0)^gama);
            end
        end
        t1_2 = toc(t1_1);
        disp(num2str(t1_2));
    end
    
    img_hsv_out = img_hsv;
    img_hsv_out(:, :, 3) = img_V_out ./ 255;
    img_out = hsv2rgb(img_hsv_out);
    
    figure(2);
    imshow(img_out, []);
    title('增強圖像');
    
else
    disp('輸入需要彩色圖像');
end

計算積分圖

function img_int = boxFilter(img)
% inputs:
%       img:
% outputs:
%        img_int:
% Author: HSW
% Date: 2018-04-27

img_int = zeros(size(img));
[rows, cols, dims] = size(img);

for i = 1:rows
    for j = 1:cols
        for dim = 1:dims
            img_int(i, j, dim) =  img(i, j, dim);
            if i - 1 > 0
                img_int(i, j, dim) = img_int(i, j, dim) + img_int(i - 1, j, dim);
            end
            if j - 1 > 0
                img_int(i, j, dim) = img_int(i, j, dim) + img_int(i, j-1, dim);
            end
            if i - 1 > 0 && j - 1 > 0
                img_int(i, j, dim) = img_int(i, j, dim)  - img_int(i - 1, j -1, dim);
            end
        end
    end
end

end

3. 模型效果