MATLAB: How to find the highest 5 adjacent pixels in a matrix

connected pixels

Hi, I am trying to find the 5 highest value pixels in a matrix. The drawback is that the pixels need to be connected. So, if I have:

X=
       9.1113       64.762       23.623       77.029       25.644
       57.621       67.902        11.94       35.022       61.346
       68.336       63.579        60.73       66.201       58.225
       54.659       94.517       45.014       41.616       54.074
       42.573       20.893       45.873       84.193       86.994
       64.444       70.928       66.194       83.292       26.478

I would want something like:

B= 
       0       0        0       0       0
       0       0        0       0       0
       0       0        0       0       0
       0       0        0       0       0
       0       0       45.873   84.193  86.994
       0       0       66.194   83.292  0

Any ideas on how to achieve this?

Thank you in advance!

Best Answer

The only way I can think of solving this is to calculate the convolution of your matrix with all possible 5 pixel patterns. You only need to generate the patterns in one quadrant, but with 8-connected components, it's still a lot of patterns:

conv2(yourimage, [1 1 1 1 1], 'valid')
conv2(yourimage, [1 1 1 1 0; 0 0 0 0 1], 'valid')
...
conv2(yourimage, eye(5), 'valid');
...
conv2(yourimage, [1 0; 1 0; 1 0; 1 0; 0 1], 'valid')
conv2(yourimage, [1; 1; 1; 1; 1], 'valid')

The location of the maximum of each convolution is the top-left corner of the corresponding 5 pixel pattern with the maximum sum. The maximum of these maximum is what you're looking for.

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Try this

x1=[0.155,0.16,0.165,0.17,0.175,0.18,0.185,0.19,0.195,0.2,0.205,0.21,0.215,0.22,0.225,0.23,0.235,0.24,0.245,0.25,0.255,0.26,0.265,0.27,0.275,0.28,0.285,0.29,0.295,0.3,0.305,0.31,0.315,0.32,0.325,0.33,0.335,0.34,0.345,0.35,0.355,0.36,0.365,0.37,0.375,0.38,0.385,0.39,0.395,0.4,0.405,0.41,0.415,0.42,0.425,0.43,0.435,0.44,0.445,0.45,0.455,0.46,0.465,0.47,0.475,0.48,0.485,0.49,0.495,0.5,0.505,0.51,0.515,0.52,0.525,0.53,0.535,0.54,0.545,0.55,0.555,0.56,0.565,0.57,0.575,0.58,0.585,0.59,0.595,0.6,0.605,0.61,0.615,0.62,0.625,0.63,0.635,0.64,0.645,0.65,0.655,0.66,0.665,0.67,0.675,0.68,0.685,0.69,0.695,0.7,0.705,0.71,0.715,0.72,0.725,0.73,0.735,0.74,0.745,0.75,0.755,0.76,0.765,0.77,0.775,0.78,0.785,0.79,0.795,0.8,0.805,0.81,0.815,0.82,0.825,0.83,0.835,0.84,0.845,0.85,0.855,0.86,0.865,0.87,0.875,0.88,0.885,0.89,0.895,0.9,0.905,0.91,0.915,0.92,0.925,0.93,0.935,0.94,0.945,0.95,0.955,0.96,0.965,0.97,0.975,0.98,0.985,0.99,0.995,1];
y1=[0.749,0.743,0.736,0.729,0.723,0.717,0.708,0.7,0.693,0.686,0.679,0.675,0.671,0.667,0.663,0.658,0.653,0.648,0.643,0.638,0.633,0.63,0.626,0.623,0.619,0.616,0.612,0.609,0.606,0.603,0.6,0.597,0.594,0.591,0.588,0.585,0.582,0.579,0.577,0.574,0.571,0.569,0.567,0.564,0.562,0.56,0.558,0.556,0.553,0.551,0.55,0.549,0.547,0.546,0.545,0.543,0.542,0.541,0.539,0.538,0.537,0.536,0.535,0.534,0.534,0.533,0.532,0.531,0.53,0.53,0.529,0.529,0.528,0.528,0.527,0.526,0.526,0.525,0.525,0.524,0.524,0.524,0.524,0.524,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.523,0.524,0.525,0.525,0.526,0.526,0.527,0.527,0.528,0.529,0.529,0.53,0.531,0.532,0.532,0.533,0.534,0.534,0.535,0.536,0.537,0.538,0.538,0.539,0.54,0.541,0.542,0.542,0.543,0.544,0.545,0.546,0.546,0.547,0.548,0.549,0.55,0.551,0.552,0.553,0.553,0.554,0.555,0.556,0.557,0.558,0.559,0.56,0.561,0.562,0.562,0.563,0.564,0.565,0.566,0.567,0.568,0.569,0.57,0.571,0.572,0.572];
ratio1 = 13;
x2=[0.305,0.31,0.315,0.32,0.325,0.33,0.335,0.34,0.345,0.35,0.355,0.36,0.365,0.37,0.375,0.38,0.385,0.39,0.395,0.4,0.405,0.41,0.415,0.42,0.425,0.43,0.435,0.44,0.445,0.45,0.455,0.46,0.465,0.47,0.475,0.48,0.485,0.49,0.495,0.5,0.505,0.51,0.515,0.52,0.525,0.53,0.535,0.54,0.545,0.55,0.555,0.56,0.565,0.57,0.575,0.58,0.585,0.59,0.595,0.6,0.605,0.61,0.615,0.62,0.625,0.63,0.635,0.64,0.645,0.65,0.655,0.66,0.665,0.67,0.675,0.68,0.685,0.69,0.695,0.7,0.705,0.71,0.715,0.72,0.725,0.73,0.735,0.74,0.745,0.75,0.755,0.76,0.765,0.77,0.775,0.78,0.785,0.79,0.795,0.8,0.805,0.81,0.815,0.82,0.825,0.83,0.835,0.84,0.845,0.85];
y2=[0.695,0.694,0.692,0.691,0.69,0.689,0.688,0.686,0.685,0.684,0.683,0.682,0.681,0.68,0.678,0.677,0.675,0.674,0.673,0.671,0.67,0.669,0.667,0.666,0.665,0.663,0.662,0.661,0.66,0.659,0.658,0.657,0.656,0.655,0.654,0.653,0.652,0.651,0.65,0.649,0.649,0.648,0.647,0.646,0.645,0.644,0.643,0.642,0.641,0.641,0.641,0.64,0.64,0.64,0.639,0.639,0.639,0.638,0.638,0.638,0.637,0.636,0.636,0.635,0.634,0.633,0.633,0.632,0.632,0.632,0.632,0.632,0.632,0.632,0.632,0.632,0.632,0.632,0.632,0.631,0.631,0.631,0.631,0.631,0.631,0.631,0.631,0.631,0.631,0.63,0.631,0.631,0.631,0.631,0.631,0.631,0.631,0.632,0.632,0.632,0.633,0.633,0.633,0.634,0.634,0.635,0.636,0.636,0.637,0.638];
ratio2 = 8.5;
% first interpolating signal1 to be of same length as signal2
x1_new = x2; % same x values as x2
y1_new = interp1(x1, y1, x1_new);
ratiox = 12;
x3 = x2; % same x values as x1_new and x2
y3 = interp1([ratio1 ratio2], [y1_new; y2], ratiox);
hold on
plot(x1_new, y1_new, 'DisplayName', 'ratio=13');
plot(x2, y2, 'DisplayName', 'ratio=8.5');
plot(x3, y3, 'DisplayName', 'ratio=12'); % values at ratio=12
legend

MATLAB: How to plot smooth curve in matlab

clc; clear all ;
x=[0 0.025 0.05 0.075 0.1 0.125 0.15 0.175 0.2 0.225 0.25 0.275 0.3 0.325 0.35 0.375 0.4 0.425 0.45 0.475 0.5 0.525 0.55 0.575 0.6 0.625 0.65 0.675 0.7 0.725 0.75 0.775 0.8 0.825 0.85 0.875 0.9 0.925 0.95 0.975 1 ] ;
y=[1.422 1.427 1.431 1.396 1.396 1.377 1.377 1.358 1.357 1.338 1.338 1.319 1.318 1.301 1.301 1.288 1.287 1.278 1.278 1.274 1.274 1.275 1.276 1.282 1.282 1.294 1.294 1.309 1.310 1.328 1.328 1.348 1.348 1.367 1.367 1.386 1.386 1.413 1.413 1.039 1.025] ;
yi = smooth(y) ;
plot(x,y,'r')
hold on
plot(x,yi,'b') ;

Best Answer

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