Splitting an edge HELP!!

Question

Francesco Pignatelli 2023-3-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1926955-splitting-an-edge-help

评论： Francesco Pignatelli 2023-3-14

edge.mat

Hello all,

I have the following edge extracted (in yellow) that I want to split in two different parts based on the line passing through the midpoint of each row between the two edges (black line)

Anyone knows how to do it? I attach the edge matrix (full image).

Thanks a lot!

Best

Francesco

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Answer 1

Adam Drake 2023-3-11

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1926955-splitting-an-edge-help#answer_1190930

编辑：Adam Drake 2023-3-13

在 MATLAB Online 中打开

edge.mat

Almost certainly not the most efficient way to do this, but it works.

load edge.mat

XLim = 1:550;

YLim = 300:1015;

subBUB = BUB(YLim,XLim);

y1 = 0; y2 = 716;

x1 = 0; x2 = 425;

m = (y1 - y2)/(x1 - x2);

x = XLim;

y = m * (x - x1) + y1;

top = zeros(size(subBUB));

bottom = zeros(size(subBUB));

for r = 1:size(subBUB,1)

for c = 1:size(subBUB,2)

if r < m * (c - x1) + y1 % less-than because of y-axis inversion on imagesc plot

top(r,c) = subBUB(r,c);

else

bottom(r,c) = subBUB(r,c);

end

figure

subplot(1,3,1)

imagesc(subBUB)

title('Original')

line(x,y,'Color','black')

subplot(1,3,2)

imagesc(top)

title('Top')

line(x,y,'Color','black')

subplot(1,3,3)

imagesc(bottom)

title('Bottom')

line(x,y,'Color','black')

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Adam Drake 2023-3-13

Reconstruct the top and bottom pieces back together or use a spline instead of a linear function to define the split?

Francesco Pignatelli 2023-3-13

I mean use a spline to "smooth" the two edges once they're splitted.

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Answer 2

Adam Drake 2023-3-14

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1926955-splitting-an-edge-help#answer_1193125

在 MATLAB Online 中打开

edge.mat

Your second question was an entirely different problem. I had to vectorize the image, do a spline, then recombine. Increasing stepsize will smooth your spline but reduce the number of output pixels. You could do an initial spline at a large step size and a second spline with a stepsize of 1, but I think you can handle that. This is where I say adieu.

Please Accept the Answer! Thanks!

clc, clear variables, close all

load edge.mat

XLim = 10:550;

YLim = 300:1015;

subBUB = BUB(YLim,XLim);

y1 = 0; y2 = 716;

x1 = 0; x2 = 425;

m = (y1 - y2)/(x1 - x2);

x = XLim;

y = m * (x - x1) + y1;

top = zeros(size(subBUB));

bottom = zeros(size(subBUB));

for r = 1:size(subBUB,1)

for c = 1:size(subBUB,2)

if r < m * (c - x1) + y1

top(r,c) = subBUB(r,c);

else

bottom(r,c) = subBUB(r,c);

end

figure

subplot(1,3,1)

imagesc(subBUB)

title('Original')

line(x,y,'Color','black')

subplot(1,3,2)

imagesc(top)

title('Top')

line(x,y,'Color','black')

subplot(1,3,3)

imagesc(bottom)

title('Bottom')

line(x,y,'Color','black')

% Convert img matrices to vectors

[yt,xt] = find(top);

[yb,xb] = find(bottom);

%% Spline

stepsize = 1;

xxt = min(xt):stepsize:max(xt);

xxb = min(xb):stepsize:max(xb);

% Spline function requires unique values

[xt_d,ut_idx,~] = unique(xt);

yt_d = yt(ut_idx);

[xb_d,ub_idx,~] = unique(xb);

yb_d = yb(ub_idx);

yyt = spline(xt_d,yt_d,xxt);

yyb = spline(xb_d,yb_d,xxb);

figure

subplot(1,2,1)

plot(xt,yt)

set(gca, 'YDir','reverse')

title('Top')

subplot(1,2,2)

plot(xb,yb)

set(gca, 'YDir','reverse')

title('Bottom')

figure

subplot(1,2,1)

plot(xxt,yyt)

set(gca, 'YDir','reverse')

title('Top')

subplot(1,2,2)

plot(xxb,yyb)

set(gca, 'YDir','reverse')

title('Bottom')

%% Recombine

% Preallocate array

out = zeros(size(subBUB));

% make x and y values integers (introduces a bit of error)

xt_out = round(xxt);

xb_out = round(xxb);

yt_out = round(yyt);

yb_out = round(yyb);

% Put 1 at x and y values

for i = 1:length(xt_out)

r = yt_out(i);

c = xt_out(i);

out(r,c) = 1;

end

for i = 1:length(xb_out)

r = yb_out(i);

c = xb_out(i);

out(r,c) = 1;

end

figure

imagesc(out)

title('Recombined')

line(x,y,'Color','black')

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Francesco Pignatelli 2023-3-14

Hej! Of course I accept it! Thanks a ton!! :D

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