change an image from rectangular to square by adding white area

조회 수: 11(최근 30일)
hamsa dhia
hamsa dhia 2022년 11월 17일
댓글: Rik 2022년 11월 17일
Dears, i have a dataset that im working on but all of them in rectangular shape, i wand them to be square by adding white area ( raws or coloumns depending on the image) many thanks in advanced
  댓글 수: 2
hamsa dhia
hamsa dhia 2022년 11월 17일
편집: hamsa dhia 2022년 11월 17일
i tried this code but it add black margin to the image , i need to fill the lack of pixels in white not black please
im = imread('1.jpg');
nrows = size(im,1);
ncols = size(im,2);
d = abs(ncols-nrows); % difference between ncols and nrows:
if(mod(d,2) == 1) % if difference is an odd number
if (ncols > nrows) % we add a row at the end
im = [im; zeros(1, ncols)];
nrows = nrows + 1;
else % we add a col at the end
im = [im zeros(nrows, 1)];
ncols = ncols + 1;
end
end
if ncols > nrows
im = padarray(im, [(ncols-nrows)/2 0]);
else
im = padarray(im, [0 (nrows-ncols)/2]);
end
figure; imshow(im)

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답변(2개)

Rik
Rik 2022년 11월 17일
편집: Rik 2022년 11월 17일
The documentation for padarray states it will pad with 0. If you don't want that, you will have to provide the value as the third argument. You probably want 255, but you can use the code below to determine that dynamically.
switch class(im)
case 'uint8'
padval = uint8(255);
case 'double'
padval = 1;
otherwise
error('check what value you need')
end
Edit: a much better solution that this code is to use the function that @DGM showed in his answer: getrangefromclass.
range = getrangefromclass(im)
padval = range(2);
  댓글 수: 3

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DGM
DGM 2022년 11월 17일
편집: DGM 2022년 11월 17일
I don't normally use getrangefromclass(), but that's one way to get the white value. Of course, it's impossible to tell that the result is padded here because it's displayed on a white background
inpict = imread('peppers.png');
%inpict = rot90(inpict); % will pad either dimension
outpict = squarewhitematting(inpict);
imshow(outpict)
function outpict = squarewhitematting(inpict)
% add symmetric white padding to the smaller dimension of the image geometry
% so that the resulting image is square
% INPICT is an image of any standard image class, with any number of channels.
% multiframe images are supported
% get nominal black and white value
valuerange = getrangefromclass(inpict);
[h,w,~] = size(inpict);
if h == w
% nothing to do
outpict = inpict;
return;
else
if w > h % wide image; pad top/bot
padamt = [(w-h)/2 0];
else % tall image; pad l/r
padamt = [0 (h-w)/2];
end
% use floor/ceil to deal with odd differences
outpict = padarray(inpict,floor(padamt),valuerange(2),'pre');
outpict = padarray(outpict,ceil(padamt),valuerange(2),'post');
end
end
  댓글 수: 4
Rik
Rik 2022년 11월 17일
Something strange is going on if that line doesn't work. image is the primitive that is called by imshow (just like plot calls line and surf calls patch).
But if you have a working solution now, that should do it. There is no fundamental difference between the code I suggested and what DGM implemented (other than that DGM provided you with a full implementation).

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