在MATLAB中的图像中绘制黑色矩形

Question

I'm facing a problem. I'm writing a script and wanted to apply this effect on a white image.

But now my image appears like this.

I'm stuck on this i write two for loops one for rows and second for columns which draw black lines according to image size 800x450 but how i draw black boxes.

Script:

        clear all;
        close all;
        clc;
        image = rgb2gray(imread('4.jpg'));
        b = cast(image,'double');
        out = 60*((b)./(max(max(b))));

        out = out + 195;

        [r,c,d] = size(out);

        x = floor(r/80);

        y = floor(c/160);

        %x rows
        for i = 1 : 88 : 450
            %  replaceable line
            out(i:i+x,:,:) = 0;

        end



        %y columns
        for i = 1 : 88 : 800
            %  replaceable line
            out(:,i:i+y,:) = 0;
        end

        final = cast(out,'uint8');

        imshow(final);

Answer 1

The trick for drawing a checkerboard, is to find cases where the x and y indices (when added together) are either odd or even.

sz = size(img);
[row, col] = ndgrid(1:sz(1), 1:sz(2));
checkers = logical(mod(row + col, 2));

Or more simply

checkers = bsxfun(@(x,y)mod(x + y, 2), 1:size(img, 1), (1:size(img, 2)).').';

This will return a matrix with 0 (black) and 1 (white) checkers.

If you want to change the size of the checkers you could do something like this.

sz = size(img);
checkersize = 10;
[row, col] = ndgrid(1:sz(1), 1:sz(2));
checkers = logical(mod(ceil(row / checkersize) + ceil(col/checkersize)),2);

Or simply

checkersize = 10;
checkers = bsxfun(@(x,y)mod(ceil(x/checkersize) + ceil(y/checkersize), 2), 1:size(img, 1), (1:size(img, 2)).').';

If you actually want to apply this effect to an image, you can use the checkers matrices above to index into your image and set values similar to this answer

replacementColor = [0 0 0];                         % RGB
reshaped_image = reshape(img, [], 3);               % Flatten first two dims
C = repmat(replacementColor, [sum(checkers(:)), 1]);% Make color correct size
reshaped_image(checkers, :) = C;                    % Replace color
newImage = reshape(reshaped_image, size(img));      % Shape it back into original

Answer 2

You can use this part of code:

image = ones(450,800,3);%create white image
[row_len,column_len,rgb] = size(image);
side_vert = floor(row_len/5);
side_hor  = floor(column_len/9);
color = 1;
for(i = 1:side_vert:row_len)
    for(j = 1:side_hor:column_len - side_hor)
        if(color == 0)
            image(i:side_vert - 1 + i,j:j + side_hor - 1,:) = 0;
            color = 1;
        else
            color = 0;
        end;
    end;
end;
imshow(image);

Answer 3

You can also use the checkerboard function:

k = 30;   %// size of each square in the checkerboard
img = checkerboard(k) < 0.5;   

For some reason the function makes half of the checkerboard gray, so you have to use < 0.5 (or > 0.5 , depending on the ordering you want) to give you just the black and white image.