How to figure a colour based on a matrice of 1-by-3

Question

arman Yaraee 2011-10-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/18922-how-to-figure-a-colour-based-on-a-matrice-of-1-by-3

This is my code:

%%In this part we just find the coordinates of the required colours
im = imread('Lighthouse.jpg');
n = 4;
figure, imshow(im)
[x,y] = ginput(n);
x = floor(x);
y = floor(y);
%colour(length(x),3);
for i=1:length(x)
      for j=1:3
          colour(i,j) = im(y(i),x(i),j);
      end
end
image(colour)

when I run it, and slect a point on the image it doesn't show me the colour I selected!! it figures a red colour!! why is that? the variable colour is [195,213,223]

how can I visualize that RGB colour?

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Answer 1

Image Analyst 2011-10-20

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https://ww2.mathworks.cn/matlabcentral/answers/18922-how-to-figure-a-colour-based-on-a-matrice-of-1-by-3#answer_25304

在 MATLAB Online 中打开

Well you messed up in a couple of places. Try this:

im = imread('peppers.png');
n = 4;
figure, imshow(im)
[x,y] = ginput(n);
x = floor(x);
y = floor(y);
%colour(length(x),3);
colour = zeros(length(x), 1, 3, 'uint8');
for i=1:length(x)
  for j=1:3
    colour(i,1, j) = im(y(i),x(i),j);
  end
end
image(colour)

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arman Yaraee 2011-10-21

yes my friend thank you. I figured it out last night! my problem was making colour 2-D array. I should make it a 3-D array in order to make this work!

Also thanks a lot. your way is better than mine.

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Answer 2

the cyclist 2011-10-20

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https://ww2.mathworks.cn/matlabcentral/answers/18922-how-to-figure-a-colour-based-on-a-matrice-of-1-by-3#answer_25290

Divide by 255. MATLAB uses the convention of RGB values from (0,1). This was discussed on this forum a few weeks ago, but for some reason I can't find it.

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arman Yaraee 2011-10-20

sorry I didn't undrestand the word u just said! I am new to matlab. I tried dviding it by 255. it become a matrice from 0-1. this is the amount of brightness. my question is how to visualize the matrice colour as a color so I can see it works!

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