border of random colour around grey image

Hi,

I was wondering how would you put a border of random colour (50 mpixels wide) around the grey image?? Just stuck on how to approach it. I have attached the iamge I have used.

An image in what it suppose to look like:

The code i have done so far:

owl = imread('owl.jpg');
owl_eye=owl;
owl_eye=owl_eye(350:450,600:710,:)
figure
imshow(owl_eye,'InitialMagnification', 'fit');
owleye_gray=rgb2gray(owl_eye);
figure
imshow(owleye_gray,'InitialMagnification', 'fit');

Answer 1

[Image Analyst]

Use the color thresholder app on the Apps tab of the tool ribbon to create a mask for the yellow owl eyes. Use hsv color space. Then use bwareafilt() to get only the two eyes

mask = bwareafilt(mask, 2); % Extract 2 largest blobs.

Then use bwconvhull to get the convex hull of them and then use regionprops to get the bounding box:

mask = bwconvhull(mask); % Combine two eyes into one blob.
props = regionprops(mask, 'BoundingBox'); % Get bounding box of the single blob.
hold on;
% Put random colored box in the overlay above the image.
rectangle('Position', props.BoundingBox, 'Color', rand(1, 3)); % Box in random color over image.

Post your code with any problems.

[Oscar Tsang]

Didn't know you can do it that way. But I thought there was a way similar to this,

where you find the edge of the image then set the border width to 50 pixels

owleye_gray([51:70,end-70:end-51],:,:)=255;

[Image Analyst]

I've never ever seen anyone index in that way, where you're giving a 2-D array as the first index and taking all columns and all colors. Exactly what is this supposed to do? It's highly unusual, if it even works at all.

[Oscar Tsang]

the question is:

(d)* Convert the eye image to grey scale. Add a border of random colour (50 pixels on each side) around the grey image. The expected output is the image i have provided. I already written some code for it.

[Walter Roberson]

That is not a two-dimensional array as the first index: it is just a vector. The effect would be to leave the upper and lower 50 pixels alone, and set the next 20 to white. I suspect you would want more

ws = 50;
ww = 20;
owleye_gray([ws+1:ws+ww, end-ww-ws:end-ws+1], [ws+1:ws+ww, end-ww-ws:end-ws+1], :) = 255;

[Image Analyst]

Use padarray() to add a random value in a border of specified width around your image.

B = padarray(A,padsize,padval)

Do that for every color channel, then combine. Something like (untested)

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
% Pad with random number from 1 - 255.
redChannel = padarray(redChannel, 50, randi(255));
greenChannel = padarray(greenChannel, 50, randi(255));
blueChannel = padarray(blueChannel, 50, randi(255));
% Recombine separate color channels into a single, true color RGB image.
rgbImage = cat(3, redChannel, greenChannel, blueChannel);

[Oscar Tsang]

How would a merge that with my image, i tried but eror keep saying redchannel undefined fucntion.

[Oscar Tsang]

I managed to get it to work but it only places a border on the top and bottom, not the sides

[Image Analyst]

Oscar:

Yes, that's weird. Same for me. Maybe I'll call the Mathworks tomorrow and ask them about it. Meanwhile, my code is attached.

[DGM]

The length of padsize defines which dimensions get padded; padarray() does not expand padsize if it's specified as a scalar. As a consequence, only the first dimension will get padded.

Answer 2

[DGM]

While this answer covers a number of ways to get a border on an image, it also demonstrates that getting a colored border is a bit inconvenient using MATLAB/IPT tools. Considering that, I'm going to use MIMT addborder() as described therein.

A = imread('peppers.png');

bcolor = rand(1,3); % random color
B = addborder(A,10,bcolor,'normalized');

Of course, instead of an entirely random color, you could draw colors randomly from a color table:

A = imread('peppers.png');

cmap = parula(64);
bcolor = cmap(randi([1 size(cmap,1)],1,1),:);
B = addborder(A,10,bcolor,'normalized');

... that would at least keep everything within a specified color scheme:

A = imread('peppers.png');
A = imresize(A,0.5); % don't need a bunch of big images for a demo

cmap = parula(64);
B = cell(4,1);
for f = 1:numel(B)
    bcolor = cmap(randi([1 size(cmap,1)],1,1),:);
    B{f} = addborder(A,5,bcolor,'normalized');
end

montage(B)