How can I delete the part of the image if the black area exists in the image?

Question

Drov 2023-3-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1922515-how-can-i-delete-the-part-of-the-image-if-the-black-area-exists-in-the-image

评论： DGM 2023-4-1

2.png
1.png

在 MATLAB Online 中打开

Dear sir,

I have 22x224x3 image and divided 4 part region. Please see my attchment photo.

In the image, left_bottom and right_bottom have black area. How can I remove part of image ( from 4 part) if black area exists.

In this example, I want to delete two part (left_bottom_region and right_bottom_region - they have black area) and recombine (left_top_region and right_top_region - they havn't black area)

Someone can help me, please? Thanks a lot with respect.

FaceCrop = imread("1.png");

left_top_region = FaceCrop(1:112, 1:112, :); figure,subplot(2,2,1);imshow(left_top_region);

right_top_region = FaceCrop(1:112, 112:224, :);subplot(2,2,2);imshow(right_top_region);

left_bottom_region = FaceCrop(112:224, 1:112, :);subplot(2,2,3);imshow(left_bottom_region);

right_bottom_region = FaceCrop(112:224, 112:224, :);subplot(2,2,4);imshow(right_bottom_region);

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Drov 2023-3-30

1111.jpg

Hello!

Firstly, thanks for your reply. Here I attached photo. Please see the photo.

In the photo, black rectangle area have in face. How can I remove if black pixels area have in image, please?

Walter Roberson 2023-3-30

It is not possible to have an array with a "hole" in it, so what do you want to replace the black pixels with?

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Answer 1

Image Analyst 2023-3-31

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https://ww2.mathworks.cn/matlabcentral/answers/1922515-how-can-i-delete-the-part-of-the-image-if-the-black-area-exists-in-the-image#answer_1205309

在 MATLAB Online 中打开

1111.JPG

Try this:

% Demo by Image Analyst
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;
%===============================================================================
% Get the name of the image the user wants to use.
baseFileName = '1111.jpg';
folder = pwd;
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
    % The file doesn't exist -- didn't find it there in that folder.
    % Check the entire search path (other folders) for the file by stripping off the folder.
    fullFileNameOnSearchPath = baseFileName; % No path this time.
    if ~exist(fullFileNameOnSearchPath, 'file')
        % Still didn't find it.  Alert user.
        errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
        uiwait(warndlg(errorMessage));
        return;
    end
end
%=======================================================================================
% Read in image.
rgbImage = imread(fullFileName);
% Get the dimensions of the image.
[rows, columns, numberOfColorChannels] = size(rgbImage)
% Take just the left half of the image
middleColumn = columns / 2;
rgbImage = rgbImage(:, 1 : middleColumn, :);
% Display image.
subplot(2, 2, 1);
imshow(rgbImage, []);
impixelinfo;
axis on;
caption = sprintf('Original RGB Image\n%s', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Set up figure properties:
% Enlarge figure to full screen.
g = gcf;
g.WindowState = "maximized";
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
drawnow;
%--------------------------------------------------------------------------------------------------
% Find the black rectangle
[r,g,b] = imsplit(rgbImage);
mask = (r == 0) & (g == 0) & (b == 0);
% Take the largest blob.
mask = bwareafilt(mask, 1);
% Fill any holes.
mask = imfill(mask, 'holes');
% Display image.
subplot(2, 2, 2);
imshow(mask, []);
impixelinfo;
axis on;
title('Mask', 'FontSize', fontSize, 'Interpreter', 'None');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
drawnow;
%--------------------------------------------------------------------------------------------------
% Get bounding box.
props = regionprops(mask, 'BoundingBox');
column1 = floor(props.BoundingBox(1))
column2 = ceil(column1 + props.BoundingBox(3))
row1 = floor(props.BoundingBox(2))
row2= ceil(row1 + props.BoundingBox(3))
%---------------------------------------------------------------------------------------
% Delete rows that have the black rectangle in them.
rgbImage2 = rgbImage; % Make a copy.
rgbImage2(row1:row2, :, :) = [];
% Display image.
subplot(2, 2, 3);
imshow(rgbImage2, []);
impixelinfo;
axis on;
caption = sprintf('After Rows %d - %d removed', row1, row2);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
%---------------------------------------------------------------------------------------
% Delete columns that have the black rectangle in them.
rgbImage2(:, column1 : column2, :) = [];
% Display image.
subplot(2, 2, 4);
imshow(rgbImage2, []);
impixelinfo;
axis on;
caption = sprintf('After Columns %d - %d removed', column1, column2);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.

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Answer 2

DGM 2023-3-31

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https://ww2.mathworks.cn/matlabcentral/answers/1922515-how-can-i-delete-the-part-of-the-image-if-the-black-area-exists-in-the-image#answer_1205724

移动：Image Analyst 2023-3-31

在 MATLAB Online 中打开

Alternatively, you might want to keep all those surrounding pixels.

inpict = imread('plsremovethepixels.jpg');

% create a mask describing the area to be preserved

mask = rgb2gray(inpict)<4;

mask = bwareafilt(mask,2);

mask = imopen(~mask,ones(21));

mask = imclose(mask,ones(21));

mask = imdilate(mask,ones(3));

% find all candidate geometries for this number of pixels

sz0 = size(mask);

sz = factor2(nnz(mask),'ordered',false);

% select the one with aspect ratio most similar to the original

ar0 = (min(sz0(1:2))/max(sz0(1:2)));

ar = sz(:,1)./sz(:,2);

[~,idx] = min(abs(ar - ar0));

sz = [sz(idx,:) size(inpict,3)];

% mask and reshape into a new rectangular image with no holes

mask = repmat(mask,[1 1 size(inpict,3)]);

outpict = inpict(mask);

outpict = reshape(outpict,sz);

imshow(outpict)

Okay so maybe keeping all the pixels isn't totally necessary. Maybe we just want to close the hole using the surrounding image.

inpict = imread('plsremovethepixels.jpg');

% create a mask describing the area to be removed

mask = rgb2gray(inpict)<5;

mask = bwareafilt(mask,2);

mask = imclose(mask,ones(21));

mask = imopen(mask,ones(21));

mask = imdilate(mask,ones(3));

% fill the masked region with NaN

outpict = im2double(inpict);

outpict(repmat(mask,[1 1 size(inpict,3)])) = NaN;

% sift pixels radially inward to move empty region to the edges

outpict = siftpixels(outpict,'c');

% crop off empty fringes

outpict = imcrop(outpict,[47 22 177 237]);

imshow(outpict)

Or maybe instead of moving the surrounding pixels, we can just fill the region based on them!

inpict = imread('plsremovethepixels.jpg');

% create a mask describing the area to be removed

mask = rgb2gray(inpict)<5;

mask = bwareafilt(mask,2);

mask = imclose(mask,ones(21));

mask = imopen(mask,ones(21));

mask = imdilate(mask,ones(3));

% inpaint the selected region

outpict = inpict;

for c = 1:size(inpict,3)

outpict(:,:,c) = regionfill(outpict(:,:,c),mask);

end

imshow(outpict)

Hmm. That's still not quite good enough. Maybe we can fill it with our imagination!

inpict = imread('plsremovethepixels.jpg');

fg = imread('totallyokay.jpg');

% create a mask describing the area to be removed

mask = rgb2gray(inpict)<5;

mask = bwareafilt(mask,2);

mask = imclose(mask,ones(21));

mask = imopen(mask,ones(21));

mask = imdilate(mask,ones(3));

% fill the missing region

outpict = uint8(mask.*double(fg) + (1-mask).*double(inpict));

imshow(outpict)

... and that's why nobody pays me to draw things.

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Image Analyst 2023-3-31

移动：Image Analyst 2023-3-31

Nonetheless, it's a good demonstration of some useful techniques. siftpixels does not seem to be a built-in function, though regionfill is.

Your comment "that's why nobody pays me to draw things" made me think of this:

😀😀😀

DGM 2023-4-1

The worst part about using a tablet is how poorly it replicates the familiar feel of the natural media such as pencil on paper, felt on bristol, or crayons on drywall.

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