MATLAB Answers


Create black columns/rows in image.

Asked by Raldi
on 26 Feb 2015
Latest activity Commented on by Raldi
on 26 Feb 2015
Hi everyone,
I have an image and I want to only keep visible small patches of lets say 8x8 alternatively.
So I start at the beginning keep the first 8x8 patch, move right, make black the next patch, and so on until the end.
After that I move to the next row and I make the first patch black since we kept the one above it.
Moving like this I create a sort of a check board where the white parts have my original image.
What I did till now is
for ii = 1:it
Image = Image(1:step:end, 1:step:end);
After that I create a matrix of zeros at the dimensions of my original image and paint my under-sampled image
imageNew(1:step:end, 1:step:end) = Image;
This does not create the check-board effect though and I don't even know if it is good enough regarding the time it needs to run.
Has anyone any idea of how to go on about doing this?


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2 Answers

Answer by Guillaume
on 26 Feb 2015
 Accepted Answer

I would do it like this:
pattern = zeros(11, 10); %number of rows must be odd
pattern(1:2:end) = 1;
mycheckerboard = imresize(pattern, 30, 'nearest');


Hi Guillaume, this creates an actual check board image. What I want is instead of having the white parts, having what my image was supposed to have at those parts..
Oh, sorry misunderstood. Just to this then:
mycheckerboard = imresize(pattern, size(myimage), 'nearest');
myimage = immultiply(myimage logical(mycheckerboard));
I am accepting this answer since it will help whoever read this to acieve what he want faster.

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Answer by Image Analyst
on 26 Feb 2015

Why not simply use the checkerboard() function?????


No idea such a thing existed. Yet if possible I was more interested to do it myself not with a function by matlab.
Then I'd just create one line then use repmat twice. I would not use Image as the name of a variable since image() is the name of a built-in function.
I will try both suggestions and see how they work. Thanks for your time.

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