How to draw a line/vector between start and end point of a movement between two images

hi all! my task is to detect differences between two images. I have two images taken with a tripod and there is only a car moving and I want to draw a vector between the front bumpers and use it as a velocity vector. I hope that it is clear enough. what i did so far is:

clear all, close all, clc
first=imread('first.jpg');
second=imread('second.jpg');
gray1=rgb2gray(first);
gray2=rgb2gray(second);
fs=abs(gray1-gray2);
sf=abs(gray2-gray1);
sf(sf<100)=[0];
sf_open = bwareaopen(sf,75); %deletes the pixels smaller than 75
fs(fs<100)=[0];
fs_open = double(bwareaopen(fs,75)); %deletes the pixels smaller than 75
l=abs(fs_open+sf_open);
imtool(l);
se1 = strel('square',5);
l_dilate = imdilate(l,se1);
imtool(l_dilate) %combines close values to have a better view

and my outcome is this:

I am satisfied with the image as it contains only 1 and 0 in the matrix. Now I dont know how can I do the vector and maybe even calculate the speed of the car from this two images (I have the time information from the exif info of the pictures).

Any ideas to draw the velocity vector?

thanks

Answer 1

[Image Analyst]

Keep them as two separate images. Then call bwareafilt() or bwareaopen() to get rid of small noise specks, if any. Then call bwconncomp() and regionprops() to get the bounding boxes. From the bounding boxes, determine the right most edge.

[Okan Can Yalcindag]

hello, thank you for your answer. I am quite new with matlab and also image processing.

the thing is that I need matlab to draw the vector but somehow I could not have enough explanation about the "bwconncomp" and "regionprops" can you be a bit more specific? maybe use my codes?

thank you very much

[Image Analyst]

Possibly, if you attach first.jpg and second.jpg.

[Okan Can Yalcindag]

first:

second:

here you go