How to plot diagonal lines starting at the last line's end point?

Hello, I want to plot these red lines between each blue line, like the one all the way at the bottom but all the way up (like the red diagonals connecting the blue lines in the second picture). Any help appreciated!

img = double(mat2gray(imread('071318.bmp')));
mask_size=[5 5];
sigma=4;
Gaussian_filter = fspecial('gaussian',mask_size,sigma);
A=conv2(img, Gaussian_filter, 'same');
Gx = [-1, 0, 1; -2, 0, 2; -1, 0, 1];
Gy = [1, 2, 1; 0, 0, 0; -1, -2, -1];
SobelX = conv2(A, Gx, 'same');
SobelY = conv2(A, Gy, 'same');
gradient_direction = (atan2(SobelY, SobelX))*180/pi;
gradient_magnitude = sqrt((SobelX.^2) + (SobelY.^2));
Threshold_High = min(min(gradient_magnitude))+max(max(gradient_magnitude))*.09;
Threshold_Low = Threshold_High/2;
rows=size(A,1);
columns=size(A,2);
for i=1:rows
    for j=1:columns
        if (gradient_direction(i,j)<0) 
            gradient_direction(i,j)=360+gradient_direction(i,j);
        end
    end
end
edge_direction=zeros(rows,columns);
for i = 1  : rows
    for j = 1 : columns
        if ((gradient_direction(i,j)>=0)&&(gradient_direction(i,j)<22.5)||(gradient_direction(i,j)>=157.5)&&(gradient_direction(i,j)<202.5)||(gradient_direction(i,j)>=337.5)&&(gradient_direction(i,j)<=360))
            edge_direction(i,j)=0;
        elseif((gradient_direction(i,j)>=22.5)&&(gradient_direction(i,j)<67.5)||(gradient_direction(i,j)>=202.5)&&(gradient_direction(i,j)< 247.5))
            edge_direction(i,j)=45;
        elseif((gradient_direction(i,j)>=67.5&&gradient_direction(i,j)<112.5)||(gradient_direction(i,j)>=247.5&&gradient_direction(i,j)<292.5))
            edge_direction(i,j)=90;
        elseif((gradient_direction(i,j)>=112.5&&gradient_direction(i,j)<157.5)||(gradient_direction(i,j)>=292.5&&gradient_direction(i,j)<337.5))
            edge_direction(i,j)=135;
        end
    end
end
edge1 = zeros (rows, columns);
for i=2:rows-1
    for j=2:columns-1
        if (edge_direction(i,j)==0)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i,j+1),gradient_magnitude(i,j-1)]));
        elseif (edge_direction(i,j)==45)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i+1,j-1),gradient_magnitude(i-1,j+1)]));
        elseif (edge_direction(i,j)==90)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i+1,j),gradient_magnitude(i-1,j)]));
        elseif (edge_direction(i,j)==135)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i+1,j+1),gradient_magnitude(i-1,j-1)]));
        end
    end
end
edge2 = edge1.*gradient_magnitude;
Threshold_Low = Threshold_Low * max(max(edge2));
Threshold_High = Threshold_High * max(max(edge2));
edge_binary = zeros (rows, columns);
for i = 1  : rows
    for j = 1 : columns
        if (edge2(i, j) < Threshold_Low)
            edge_binary(i, j) = 0;
        elseif (edge2(i, j) > Threshold_High)
            edge_binary(i, j) = 1;
        elseif(edge2(i+1,j)>Threshold_High||edge2(i-1,j)>Threshold_High||edge2(i,j+1)>Threshold_High||edge2(i,j-1)>Threshold_High||edge2(i-1,j-1)>Threshold_High||edge2(i-1,j+1)>Threshold_High||edge2(i+1,j+1)>Threshold_High||edge2(i+1,j-1)>Threshold_High)
            edge_binary(i,j)=1;
        end
    end
end
edge = (edge_binary.*255);
edge(1600:2054,:)=[];
edge(:,1:300)=[];
edge=flipud(edge);
[y,x]= find(edge==255);
T= table(x,y,'VariableNames',{'x','y'}); %table of (x,y) points of bubble edge
x0=mean(x(y==min(T.y)));
T(T.x>x0,:)=[];
hold on
axis equal
title('Captive Bubble Air-Liquid Interface')
xlabel('x')
ylabel('y')
e=contour(edge,'k');
y_axis=xline(x0);
for n=0:50:max(y) %delta y small
m=min(y); %starting y value of R lines at lowest bubble edge point
x1=x(y==m+n);
delete=x1>x0;
x1(delete)=[];
x1=mean(x1);
plot([x0 x1],[m+n m+n],'b'); %R line
R=x0-x1;
    for o=m:100:max(y) %delta y big
        plot([x0 x1],[m m+n],'r');
     end
end

[darova]

Is it correct?

[Cameron Calder]

No, the red diagonals connecting the blue lines where they meet with the black edge- its hard to see in that picture sorry, I'll show it more clearly here.

[darova]

Can you please show the original image and image you want to get?

Maybe you have x,y data of the bubble not just an image?

[Cameron Calder]

Here is the original image- inputting T in the command window should return a table of all the edge point values on the left side of the bubble, which is what I'm interested in. Also heres the code from the other image, Im essentially trying to do this at every point on the bubble, i.e. find the red diagonal between the two green at every midpoint between three blue, or in intervals of 100.

img = double(mat2gray(imread('071318.bmp')));
mask_size=[5 5];
sigma=4;
Gaussian_filter = fspecial('gaussian',mask_size,sigma);
A=conv2(img, Gaussian_filter, 'same');
Gx = [-1, 0, 1; -2, 0, 2; -1, 0, 1];
Gy = [1, 2, 1; 0, 0, 0; -1, -2, -1];
SobelX = conv2(A, Gx, 'same');
SobelY = conv2(A, Gy, 'same');
gradient_direction = (atan2(SobelY, SobelX))*180/pi;
gradient_magnitude=sqrt((SobelX.^2) + (SobelY.^2));
Threshold_High = min(min(gradient_magnitude))+max(max(gradient_magnitude))*.09;
Threshold_Low = Threshold_High/2;
rows=size(A,1);
columns=size(A,2);
for i=1:rows
    for j=1:columns
        if (gradient_direction(i,j)<0) 
            gradient_direction(i,j)=360+gradient_direction(i,j);
        end
    end
end
edge_direction=zeros(rows,columns);
for i = 1  : rows
    for j = 1 : columns
        if ((gradient_direction(i,j)>=0)&&(gradient_direction(i,j)<22.5)||(gradient_direction(i,j)>=157.5)&&(gradient_direction(i,j)<202.5)||(gradient_direction(i,j)>=337.5)&&(gradient_direction(i,j)<=360))
            edge_direction(i,j)=0;
        elseif((gradient_direction(i,j)>=22.5)&&(gradient_direction(i,j)<67.5)||(gradient_direction(i,j)>=202.5)&&(gradient_direction(i,j)< 247.5))
            edge_direction(i,j)=45;
        elseif((gradient_direction(i,j)>=67.5&&gradient_direction(i,j)<112.5)||(gradient_direction(i,j)>=247.5&&gradient_direction(i,j)<292.5))
            edge_direction(i,j)=90;
        elseif((gradient_direction(i,j)>=112.5&&gradient_direction(i,j)<157.5)||(gradient_direction(i,j)>=292.5&&gradient_direction(i,j)<337.5))
            edge_direction(i,j)=135;
        end
    end
end
edge1 = zeros (rows, columns);
for i=2:rows-1
    for j=2:columns-1
        if (edge_direction(i,j)==0)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i,j+1),gradient_magnitude(i,j-1)]));
        elseif (edge_direction(i,j)==45)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i+1,j-1),gradient_magnitude(i-1,j+1)]));
        elseif (edge_direction(i,j)==90)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i+1,j),gradient_magnitude(i-1,j)]));
        elseif (edge_direction(i,j)==135)
            edge1(i,j)=(gradient_magnitude(i,j)==max([gradient_magnitude(i,j),gradient_magnitude(i+1,j+1),gradient_magnitude(i-1,j-1)]));
        end
    end
end
edge2 = edge1.*gradient_magnitude;
Threshold_Low = Threshold_Low * max(max(edge2));
Threshold_High = Threshold_High * max(max(edge2));
edge_binary = zeros (rows, columns);
for i = 1  : rows
    for j = 1 : columns
        if (edge2(i, j) < Threshold_Low)
            edge_binary(i, j) = 0;
        elseif (edge2(i, j) > Threshold_High)
            edge_binary(i, j) = 1;
        elseif(edge2(i+1,j)>Threshold_High||edge2(i-1,j)>Threshold_High||edge2(i,j+1)>Threshold_High||edge2(i,j-1)>Threshold_High||edge2(i-1,j-1)>Threshold_High||edge2(i-1,j+1)>Threshold_High||edge2(i+1,j+1)>Threshold_High||edge2(i+1,j-1)>Threshold_High)
            edge_binary(i,j)=1;
        end
    end
end
edge = (edge_binary.*255);
edge(1600:2054,:)=[];
edge(:,1:300)=[];
edge=flipud(edge);
[y,x]= find(edge==255);
T= table(x,y,'VariableNames',{'x','y'}); %table of (x,y) points of bubble edge
x0=mean(x(y==min(T.y)));
T(T.x>x0,:)=[];
hold on
axis equal
title('Captive Bubble Air-Liquid Interface')
xlabel('x')
ylabel('y')
e=contour(edge,'k');
m=400; 
n=100;
y_axis=xline(x0);

x1=x(y==m);
delete=x1>x0;
x1(delete)=[];
x1=mean(x1);

x2=x(y==m+n);
delete=x2>x0;
x2(delete)=[];
x2=mean(x2);

x3=x(y==m+n*2);
delete=x3>x0;
x3(delete)=[];
x3=mean(x3);

plot([x0 x1],[m m],'b'); %R1 plot
plot([x0 x2],[m+n m+n],'b'); %R2 plot
plot([x0 x3],[m+2*n m+2*n],'b'); %R3 plot

R1=x0-x1;
R2=x0-x2;
R3=x0-x3;

my2=((m+2*n)+(m+n))/2; %(mx1,my1) is midpoint between z3 and z2
mx2=(x3+x2)/2;

my1=((m+n)+m)/2; %(mx2,my2) is midpoint between z2 and z1
mx1=(x2+x1)/2;

P1=[x1 m]; %y1 point
P2=[x2 m+n]; %y2 point


plot([x1, x2], [m, m+n], 'r'); 
midX = mean([x1, x2]);
midY = mean([m, m+n]);
plot(midX, midY, 'r'); 
slope = -1/(n / (x2-x1)); 
y = slope * (x0 - midX) + midY; 
perpendicular_1=plot([x0, midX], [y, midY], 'g'); 
 
P3=[x3 m+n*2];
p4x = P3(1);
p4y = P3(2);

plot([x2 p4x], [m+n p4y], 'r'); %line from y2 to y3
midX_2 = mean([x2 p4x]);
midY_2 = mean([m+n p4y]);
plot(midX, midY, 'r'); %midpoint between y2 and y3
slope_2 = -1/((p4y-(m+n)) / (p4x-x2));
y0 = slope_2 * (x0 - midX_2) + midY_2; 
perpendicular_2=plot([x0 midX_2], [y0 midY_2], 'g'); 

syms x 
Cx=solve(slope_2 * (x - midX_2) + midY_2==slope * (x - midX) + midY,x);
Cy=slope_2 * (Cx - midX_2) + midY_2;

RP12=eval(sqrt((Cx-midX)^2+(Cy-midY)^2)); %length of RP12
RP23=eval(sqrt((Cx-midX_2)^2+(Cy-midY_2)^2)); %length of RP23
RP=double((RP12+RP23)/2); %length of RP

ratio1=(Cy-my1)/(Cx-mx1); 
alpha1=90-(atand(ratio1)); 

ratio2=(Cy-my2)/(Cx-mx2);
alpha2=90-(atand(ratio2));

theta=eval((alpha1+alpha2)/2);

RPx=x2+(RP*cosd(90-theta));
RPy=(m+n)+(RP*sind(90-theta));
plot([x2 RPx],[m+n RPy],'r'); %RP
plot([RPx RPx],[RPy m+n],'r'); 

[darova]

I have older version of MATLAB and the script doesn't want to run. Cant please you attach a screenshot or something?

[Cameron Calder]

A screenshot of the picture? It's a bmp file, the script won't run with a jpeg.

Answer 1

[darova]

Here is what i achieved

Am i succeeded?