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Table of ContentsImage 1 ............................................................................................................................ 1Histogram of the original image ............................................................................................ 1Histogram of modified image ............................................................................................... 2Previous v/s new image ....................................................................................................... 2Old image ......................................................................................................................... 2New Image ........................................................................................................................ 3Image 2 ............................................................................................................................ 4Histogram of the original image ............................................................................................ 4Histogram of modified image ............................................................................................... 5Previous v/s new image ....................................................................................................... 6Old image ......................................................................................................................... 6New Image ........................................................................................................................ 7

Image 1name = 'Sat_512_512.jpg';

Histogram of the original imagehisto(name);

2

Histogram of modified imagenew = hist_equal(name);

Previous v/s new imageold = imread(name);

Old imageimshow(old);

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New Imageimshow(new);

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Image 2name = 'Sat2_512_512.jpg';

Histogram of the original imagehisto(name);

5

Histogram of modified imagenew = hist_equal(name);

6

Previous v/s new imageold = imread(name);

Old imageimshow(old);

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New Imageimshow(new);

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Published with MATLAB® 7.14

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function [hist] = histo( name )%plots histogram of an image

a = imread(name);

hist = zeros(1,256);

for i = 1:512 for j = 1:512 val = a(i,j) + 1; hist(val) = hist(val) + 1; endend

x = 0:255;plot(x,hist);

end

Published with MATLAB® 7.14

Function to calculate histogram of the image

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function [a] = hist_equal( name )

a = imread(name);hist = histo(name);

cdf = zeros(1,256);mincdf = 0;for i=1:256 if(i==1)cdf(1) = hist(1); else cdf(i) = cdf(i-1) + hist(i); end mincdf = min(mincdf,cdf(i));end

cdf_sc = zeros(1,256);for i = 1:256 cdf_sc(i) = round(((cdf(i) - mincdf)*(255))/(262144 - mincdf));end

for i = 1:512 for j = 1:512 a(i,j) = cdf_sc(a(i,j) + 1); endend

histogram = zeros(1,256);

for i = 1:512 for j = 1:512 val = a(i,j) + 1; histogram(val) = histogram(val) + 1; endend

x = 0:255;

imshow(a);plot(x,histogram);

end

Published with MATLAB® 7.14

Function for calculating histogram equalization

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Histogram Maching

Table of ContentsFirst Image ........................................................................................................................ 1Histogram of matched image ................................................................................................ 1Matched image .................................................................................................................. 2Second Image .................................................................................................................... 3Histogram of matched image ................................................................................................ 3Matched image .................................................................................................................. 4

First Imagea = imread('Sat_512_512.jpg');

hist_a = histo(a);cdf_sc = hist_equal(a,hist_a);

for i = 1:512 for j = 1:512 a(i,j) = (norminv((cdf_sc(a(i,j)+1)/255),122,30)); endend

Histogram of matched imagehi = histo(a);x = 0:255;plot(x,hi);

Histogram Maching

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Matched imageimshow(a);

Histogram Maching

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Second Imagea = imread('Sat2_512_512.jpg');

hist_a = histo(a);cdf_sc = hist_equal(a,hist_a);

for i = 1:512 for j = 1:512 a(i,j) = (norminv((cdf_sc(a(i,j)+1)/255),122,30)); endend

Histogram of matched imagehi = histo(a);x = 0:255;plot(x,hi);

Histogram Maching

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Matched imageimshow(a);

Histogram Maching

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Published with MATLAB® 7.14

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name = 'Sat2_512_512.jpg';

img = imread(name);oimg = img;

for i = 1:510 for j = 1:510 a = zeros(3,3); for m = 1:3 for n = 1:3 a(m,n) = img(m + i - 1,n + j -1); end end %a hist = histo(a); out = hist_equal(a, hist); %out for m = 1:3 for n = 1:3 oimg(m + i - 1,n + j -1) = out(m,n); end end endend

imshow(oimg);

Published with MATLAB® 7.14

Performing local histogram equalization with a 3 x 3 mask