Getting Index in position 1 exceeds arrray bound error

I wrote a MATLAB code which will put a black box of 10 pixels width at the center of image but I am getting error which says "Index in position 1 exceeds array bounds error"

Here is the code for same

image = imread('image.jpg');
[r,c]=size(image);
width=10;
color=6;
new_image=ones(r,c)*color;
new_image=uint8(new_image);
for row=1:r
    for column=1:(c-width)/2
        new_image(row,column)=image(row,column);
    end;
    for column=(c+width)/2:c
        new_image(row,column)=image(row,column);
    end;
end;
for column=1:c
    for row=1:(r-width)/2
        new_image(row,column)=image(row,column);
    end;
    for row=(r+width)/2:c
        new_image(row,column)=image(row,column);
    end;
end;
imshow(new_image);

And for the logic of the code this code makes a matrix of ones as the size of image pixels and after that I iterate the code from the matrix and adding the pixels value of original image to the new matrix where the box is not present.

Answer 1

[Stephen23]

A better approach is to use indexing, eg.:

>> I = imread('peppers.png');
>> N = 10;
>> V = 1:N;
>> I(fix((end-N)/2)+V,fix((end-N)/2)+V,:) = 6;
>> imshow(I)

[Arihant Jain]

Thank you very much for this answer. Can you please briefly explain what this code is doing in that 4th line. I just started with MATLAB and learning things. Well thank you again for this.

[Stephen23]

"Can you please briefly explain what this code is doing in that 4th line"

I(fix((end-N)/2)+V,fix((end-N)/2)+V,:) = 6;
      (end-N)/2                             % row = midway up-down, shift down by N/2
  fix(         )+V                          % indices of N pixels starting from row
                       (end-N)/2            % col = midway left-right, shift left by N/2
                   fix(         )+V         % indices of N pixels starting from col
                                    :       % all pages (RGB has 3 pages, grayscale has 1)
I(                ,                , ) = 6; % allocate 6 to those elements of the image

You should check if that matches your definition of "middle", for both odd and even numbers of pixels.

https://www.mathworks.com/help/matlab/math/array-indexing.html

[Arihant Jain]

Thanks for your explanation. Got the point.

Answer 2

[Walter Roberson]

jpeg images are almost always rgb even when they look grey. Not always but quite rare for real grey jpeg.

When you ask for size() of an rgb image but you only provide two output variables, then the second output is not the number of columns, and is instead the number of columns multiplied by 3.

Please read the details of size() carefully.

[Arihant Jain]

Thanks for your comment I didn't knew about that. I will look into this.