Matlab影像處理(一)直方圖

 %% 直方圖

close all; clear; clc;

fprintf('影像直方圖\n\n')

img=imread('Color_lena512.bmp');

Graybar = zeros(1, 256);

Rbar = zeros(1, 256);

Gbar = zeros(1, 256);

Bbar = zeros(1, 256);

[row, col] = size(img(:, :, 1));

grayimg = rgb2gray(uint8(img));

for i=1:row

    for j=1:col

        A = grayimg(i ,j) + 1;

        Graybar(1, A) = Graybar(1, A) + 1;

        

        R = img(i, j, 1) + 1;

        Rbar(1, R) = Rbar(1, R) + 1;

        

        G = img(i, j, 2) + 1;

        Gbar(1, G) = Gbar(1, G) + 1;

        

        B = img(i, j, 3) + 1;

        Bbar(1, B) = Rbar(1, B) + 1;   

    end

end

subplot(2, 2, 1), bar(Graybar, 'k'), title('灰階直方圖')

subplot(2, 2, 2), bar(Rbar, 'r'), title('R直方圖')

subplot(2, 2, 3), bar(Gbar, 'g'), title('G直方圖')

subplot(2, 2, 4), bar(Bbar, 'b'), title('B直方圖')

%% 等化法

close all; clear; clc;

img = imread('Color_lena512.bmp');

Grayimg = rgb2gray(img);

[row, col] = size(img(:, :, 1));

outputimg = zeros(row, col);

outputbar = zeros(1, 256);

Graybar = zeros(1, 256);

cdf = zeros(1, 256);

for i=1:row

    for j=1:col

        A = Grayimg(i, j);

        Graybar(1, A) = Graybar(1, A) + 1;

    end

end

subplot(2, 2, 1), imshow(Grayimg), title('灰階原圖')

subplot(2, 2, 2), bar(Graybar), title('原直方圖')

count = 0;

for i=1:256

    for j=1:i

        cdf(1, i) = cdf(1, i) + Graybar(1, j);

    end

end

pcdf = sort(cdf);

for i=1:256

    if pcdf(1, i)>0

        cdfmin = pcdf(1, i);

        break

    end

end

L = 2.^8;

h =@(v) round( ((cdf(1, v) - cdfmin)./((row.*col) - cdfmin)).*(L - 1) )

for i=1:row

    for j=1:col

        outputimg(i, j) = h(img(i, j) + 1);

        A = outputimg(i, j) + 1;

        outputbar(1, A) = outputbar(1, A) + 1;

    end

end

subplot(2, 2, 3), imshow(uint8(outputimg)), title('灰階等化後圖')

subplot(2, 2, 4), bar(outputbar), title('等化後直方圖')