How do I use the find function to track every last point that is black, so as to create a matrix of that border between white a black image. See Below

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alex contreras 2022-1-18

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https://ww2.mathworks.cn/matlabcentral/answers/1630825-how-do-i-use-the-find-function-to-track-every-last-point-that-is-black-so-as-to-create-a-matrix-of

评论： alex contreras 2022-1-19

I used the find function to find a single point, the row at which the image is black, in the first column. But I want to do this for every column, so as to create a defined line of every row and and column, instead of a single point

clear;clc;

img1 = imread('s1.png');

img2 = imread('s2.png');

img1BW = rgb2gray(img1);

img2BW = rgb2gray(img2);

counter = 0;

for k = 1:length(img1BW);

counter = counter+1;

end

for k = 1:length(img2BW);

[r2,c] = find(img2BW(:,1:end),1,'last');

counter = counter+1;

end

Border1 = [r1,c]

Border2 = [r2,c]

final = abs(r2-r1);

fprintf('The displacement of the black border from image 1 and image 2 is : %1.000f pixels \n',final);

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alex contreras 2022-1-18

I want to create an array/matrix of every point that is on that line that dinstinguishes black from white.

alex contreras 2022-1-18

from this I can subtract every one those points from either image to find the difference.

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采纳的回答

Image Analyst 2022-1-18

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1630825-how-do-i-use-the-find-function-to-track-every-last-point-that-is-black-so-as-to-create-a-matrix-of#answer_876490

编辑：Image Analyst 2022-1-19

在 MATLAB Online 中打开

Try this. It assumes the top part is all white, and the only black is a big region along the bottom, which doesn't have to be perfectly rectangular.

[rows, columns] = size(img1BW);
topEdgeOfBlack = zeros(1, columns);
% Scan column-by-column finding out where (what row) the first black pixel 
% in each column appears.
for col = 1 : columns
    topEdgeOfBlack(col) = find(img1BW(:, col) == 0, 1, 'first');
end
hold on;
x = 1 : columns;
plot(x, topEdgeOfBlack, 'r-', 'LineWidth', 3);
hold off;

Alternatively you can find the last white pixel in each column like this:

[rows, columns] = size(img1BW);
bottomEdgeOfWhite = zeros(1, columns);
% Scan column-by-column finding out where (what row) the last white pixel 
% in each column appears.
for col = 1 : columns
    bottomEdgeOfWhite(col) = find(img1BW(:, col) > 0, 1, 'last');
end
hold on;
x = 1 : columns;
plot(x, bottomEdgeOfWhite, 'r-', 'LineWidth', 3);
hold off;

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Image Analyst 2022-1-19

在 MATLAB Online 中打开

Try this:

img1 = imread('s3.png');
img1BW = rgb2gray(img1);
imshow(img1BW);
axis('on', 'image');
impixelinfo;
[rows, columns] = size(img1BW);
bottomEdgeOfWhite = zeros(1, columns);
% Scan column-by-column finding out where (what row) the last white pixel 
% in each column appears.
for col = 1 : columns
    bottomEdgeOfWhite(col) = find(img1BW(:, col) > 0, 1, 'last');
end
hold on;
x = 1 : columns;
plot(x, bottomEdgeOfWhite, 'r-', 'LineWidth', 3);
hold off;