how to connect the adjacent lower edges of each bounding box

I have drawn a bounding box of rectangle shape on each character and save the all 4 point of all bounding box

Now I want to connect the lower edges of bounding box with each other

How to do it??

sample code for making bounding box and saving all 4 points of bounding box

I = imread('textlineImage.png');
I=im2bw(I);
I=imcomplement(I);
st=regionprops(I,'BoundingBox','Area');
allBB = zeros(length(st), 4);
for k = 1 : length(st)
    thisBB = st(k).BoundingBox;
    rectangle('Position',  [thisBB(1),thisBB(2),thisBB(3),thisBB(4)],...
    'EdgeColor', 'r', 'LineWidth', 1)
    allBB(k, :) = thisBB;
   

points are save in varibale allBB

Image is

[Rik]

You mean you want to move down the lower side of the rectangle, expanding it until they all share the same baseline? I would suggest first writing a function that determines which bounding box belongs to which line. Then you can much more easily find the mininimum value.

[praveen rai]

i just want to connect the adjacent side of each edges of bounding box(lower) with a line

[Rik]

What do you mean? The code below show two examples of what you could mean. Please adjust the code to match what you expect. Then we can help you find a way to automatically determine the required positions.

figure(1),clf(1)
subplot(1,2,1),hold on
rectangle('Position',[0 0 1 1]),rectangle('Position',[1.5 0.5 1 1])
plot([1 1.5],[0 0.5])
axis([-1 3 -1 3]),title('option 1')
subplot(1,2,2),hold on
rectangle('Position',[0 0 1 1]),rectangle('Position',[1.5 0 1 1.5])
axis([-1 3 -1 3]),title('option 2')

[praveen rai]

@rik

figure(1),clf(1)
subplot(1,2,1),hold on
rectangle('Position',[0 0 1 1]),rectangle('Position',[1.5 0.5 1 1])
plot([1 1.5],[0 0.5])
axis([-1 3 -1 3]),title('option 1')

similar to something like this I want but for better understanding what is my prob statement is I am attaching a Image in which I wrote first sentence of my image. below image u can see i draw d rectangle box with red pen and the way I want to connect my rectangle box I have drawn/highlighted with blue pen,same way I want for each line

[Rik]

What you want looks like a spline. You should look up different options for curve fitting.

[praveen rai]

u r correct i want spline(poly lines) but the prob is I am not able to write in code how to connect lower points of bounding box with each other can u help me regarding this

[Rik]

You have the coordinates right? Then what exactly is your issue?

[praveen rai]

ya I have 4 point values of rectangle box in variable allBB but which two points I have to take and how to plot for every line so that I can get spline that is the issue

I am unable to wirte these thing in loop

Answer 1

[Image Analyst]

Use kmeans on the y values to identify boxes in one of the 5 lines that your image has.

[classIndexes, classCentroid] = kmeans(y, 5);

After that, you know which line each y is in then sort by x, then use spline. Something like (untested)

y = allBB(2:4:end);
[classIndexes, classCentroid] = kmeans(y, 5);
newXSamplePoints = 1 : size(yourImage, 2)
for k = 1 : 5
    thisClass = classIndexes(k);
    thesex = sort(x(thisClass), 'ascend');
    % Fit the x to splines at every column in the image.
    newY = spline(x, y, newXSamplePoints);
end
hold on;
plot(newXSamplePoints, newY, 'm-', 'LineWidth', 2)

[praveen rai]

its showing the following error

Error using kmeans (line 247)

X must have more rows than the number of clusters.

Error in rawcode (line 25)

[classIndexes, classCentroid] = kmeans(y, 5);

allBB has value 208*4 double and y has 1*208 double