How do I create a gradient border around an image?
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I need to create a border around an image that would gradually change it's color from the image's color to white (a gradient).
Thank you.
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Accepted Answer
Walter Roberson
on 11 May 2017
borderwidth = 7; %for example
[R, C, P] = size(YourImage);
augmented_col_coords = [-borderwidth+1, 1:C, C+borderwidth];
augmented_row_coords = [-borderwidth+1, 1:R, R+borderwidth];
resample_col_coords = -borderwidth+1 : C + borderwidth;
resample_row_coords = -borderwidth+1 : R + borderwidth;
extra_line = repmat(255, 1, C+2);
augmented_red = [extra_line; 255*ones(R,1), double(YourImage(:,:,1)), 255*ones(R,1); extra_line];
gradiented_red = uint8( interp2(augmented_col_coords, augmented_row_coords, augmented_red, resample_col_coords, resample_row_coords.') );
augmented_green = [extra_line; 255*ones(R,1), double(YourImage(:,:,2)), 255*ones(R,1); extra_line];
gradiented_green = uint8( interp2(augmented_col_coords, augmented_row_coords, augmented_green, resample_col_coords, resample_row_coords.') );
augmented_blue = [extra_line; 255*ones(R,1), double(YourImage(:,:,3)), 255*ones(R,1); extra_line];
gradiented_blue = uint8( interp2(augmented_col_coords, augmented_row_coords, augmented_red, resample_col_coords, resample_row_coords.') );
gradiented_image = cat(3, gradiented_red, gradiented_green, gradiented_blue);
6 Comments
Walter Roberson
on 20 May 2017
gradiented_blue = uint8( interp2(augmented_col_coords, augmented_row_coords, augmented_blue, resample_col_coords, resample_row_coords.') );
More Answers (1)
DGM
on 16 Jul 2022
Edited: DGM
on 16 Jul 2022
You could also do this by using inpainting tools.
Using IPT regionfill():
A = imread('peppers.png');
padwidth = [30 30];
outercolor = 255; % must be scalar (black/gray/white)
% create a mask to define the transition region
mk = false([size(A,1) size(A,2)]);
mk = padarray(mk,padwidth-1,1,'both');
mk = padarray(mk,[1 1],0,'both');
% pad the image
B = padarray(A,padwidth,outercolor,'both');
% inpaint based on the mask
for c = 1:size(B,3)
B(:,:,c) = regionfill(B(:,:,c),mk);
end
imshow(B)
A = imread('peppers.png');
padwidth = [30 30];
outercolor = 255; % must be scalar (black/gray/white)
% pad the image, using NaNs to define the transition region
B = padarray(double(A),padwidth-1,NaN,'both');
B = padarray(B,[1 1],outercolor,'both');
% inpaint based on NaNs
for c = 1:size(B,3)
B(:,:,c) = inpaint_nans(B(:,:,c),2);
end
B = uint8(B); % cast back to uint8
imshow(B)
Note that both of these examples assume that input image is class uint8.
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