Remove white padding from image
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I want to remove white padding from an image (see attachment). The size of the padding is random.
So I was thinking of reading in the image and then some looping to check if the entire row/column contains the value 255. However, looping is most of the time not the best way to do stuff. So I'm wondering if there's an easier way to do this, because I've found a similar question where the rows/columns contain 0, but I don't know if this can also be used for this case (with some adjustments).
Thanks in advance.
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Accepted Answer
Walter Roberson
on 14 Oct 2018
I = imread('test-image.jpg');
W = all(I == 255, 3);
maskc = all(W, 1);
maskr = all(W, 2);
J = I;
J(maskr,:,:) = 0;
J(:,maskc,:) = 0;
image(J)
3 Comments
Walter Roberson
on 14 Oct 2018
"remove white padding" is ambiguous as to whether it should be transformed to a different color or cropped out of the image.
I = imread('test-image.jpg');
W = all(I == 255, 3);
maskc = ~all(W, 1);
maskr = ~all(W, 2);
J = I(maskr, maskc);
imshow(IM);
Nate Roberts
on 1 Apr 2020
This is exactly what I was looking for. I made a little script that can do this for an RBG image, assuming you only want to remove the padding, and not the white space within an image.
function im2 = removeWhitePadding(im1, dim)
if nargin<2
dim = 0;
end
WhitePixels = all(im1 == 255, 3);
maskr = ~all(WhitePixels, 2);
maskc = ~all(WhitePixels, 1);
if dim==1
im2 = im1(find(maskr, 1, 'first'):find(maskr, 1, 'last'),:,:);
elseif dim==2
im2 = im1(:,find(maskc, 1, 'first'):find(maskc, 1, 'last'),:);
else
im2 = im1(find(maskr, 1, 'first'):find(maskr, 1, 'last'),find(maskc, 1, 'first'):find(maskc, 1, 'last'),:);
end
end
More Answers (1)
Image Analyst
on 14 Oct 2018
Try this:
rgbImage = imread('test-image.jpg');
subplot(2, 2, 1);
imshow(rgbImage);
title('Original RGB Image', 'FontSize', 20);
axis('on', 'image');
nonWhitePixels = any(rgbImage ~= 255, 3);
subplot(2, 2, 2);
imshow(nonWhitePixels)
title('Non-white Pixels Mask', 'FontSize', 20);
axis('on', 'image');
[maskRows, maskColumns] = find(nonWhitePixels);
% Crop image
croppedImage = rgbImage(min(maskRows):max(maskRows), min(maskColumns):max(maskColumns), :);
subplot(2, 2, 3);
imshow(croppedImage);
axis('on', 'image');
title('Cropped RGB Image', 'FontSize', 20);
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/197890/image.png)
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