# Splitting an edge HELP!!

10 vues (au cours des 30 derniers jours)
Francesco Pignatelli le 11 Mar 2023
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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### Réponse acceptée

Adam Drake le 11 Mar 2023
Modifié(e) : Adam Drake le 13 Mar 2023
Almost certainly not the most efficient way to do this, but it works.
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
end
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')
##### 3 commentairesAfficher 1 commentaire plus ancienMasquer 1 commentaire plus ancien
Adam Drake le 13 Mar 2023
Reconstruct the top and bottom pieces back together or use a spline instead of a linear function to define the split?
Francesco Pignatelli le 13 Mar 2023
I mean use a spline to "smooth" the two edges once they're splitted.

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### Plus de réponses (1)

Adam Drake le 14 Mar 2023
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.
clc, clear variables, close all
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
end
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')
##### 1 commentaireAfficher -1 commentaires plus anciensMasquer -1 commentaires plus anciens
Francesco Pignatelli le 14 Mar 2023
Hej! Of course I accept it! Thanks a ton!! :D

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