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?

Answer 1

[Image Analyst]

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)

[arman Yaraee]

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.

Answer 2

[the cyclist]

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.

[arman Yaraee]

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!

Answer 3

[Walter Roberson]

Before the loop, initialize

colour = zeros(length(x),3, 'uint8');

You will then not need to do the division by 255 that The Cyclist refers to.

[arman Yaraee]

Thank you very much myfriend. tanks for pointing out the bug. but my problem still there! still when I call

image(colour);

I don't get the colour I selected. I see 3 bars of colors. sometimes, blue, yellow red or just one of these with different brightness!

[Walter Roberson]

You are selecting 4 points so you should be getting 4 colors.

You need to check whether your file is RGB (truecolor) or an indexed image (2D but you have to read in the colormap as well.)