how can i calculate distance between two points on an image

hallow

i want to calculate distance between two point on a body image. and to measure angle between two lines on an image............

Answer 1

[Image Analyst]

Use imdistline() to do it interactively. Or use hypot() or sqrt() if you know the coordinates.

[Saliha]

i want multiple point's measurement on a single image ...... compare and compute their value and then want to save their value for further use... imdistline() draws only single line.

[Image Analyst]

Well, how do you expect those lines to get there ?

If you know where they are already, just use hypot() or sqrt() like I said.

[Saliha]

i want to calculte something like this....

please visit this image...

i want to calculte distance between two feets, angle of knee and hip to which extent these bend during walk... and want differentiate using some geometrical mthods.

[Image Analyst]

Link doesn't work. And I believe I answered the question about how to find distances between two points: use imdistline to do it interactively or use sqrt() if you know the locations from some other method, like image segmentation or whatever.

[Saliha]

o.k. let me try.....

[Image Analyst]

You didn't ask how to find the vertices, only how to measure the distance between them. Presumably you're following some paper that tells you how to find the vertices. Anyway, I don't know how - I'd have to look up some papers just like you're probably doing.

[Saliha]

right.... I'm following and I've some innovative idea on it. but i don't know how to calculate and evaluate to satisfy my point..................

[Saliha]

actually i want to give these point as mouse input and after that want different calculations on it....... kindly tell me how it is possible using matlab........

[Image Analyst]

Please reread my answer. That tells you how. If you think it doesn't, then please explain why. I don't know if you overlooked in the help that imdistline() lets the user specify endpoints with the mouse. And I'm sure you learned the Pythagorean theorem in high school - it uses sqrt(). It shouldn't be very hard at all, but if you need me to actually write the lines of code for you, let me know. Try to adapt the examples in imdistline().

[Saliha]

puzzled

[Image Analyst]

Why? Were you unable to run any demos for imdistline?

[Saliha]

I've run an example but.......... can't drive my desired point .... don't know that by taking this topic I'll fall in maze :'(

[Saliha]

if u can provide me the code line then well and good

[Saliha]

but if u know about any software of "gait analysis or recognition" then pleaseeeeeeeeeeeeeee send me I'll be thankful :(

[Image Analyst]

See VisionBib

16.7.4.5 Walking, Gait Recognition, Gait Analysis
    16.7.4.5.1 Walking, Gait Recognition, University of Southampton
    16.7.4.5.2 Cyclic Motion, Periodic Motion, for Walking and Gait Recognition
    16.7.4.5.3 Human ID Using Gait, Recognition of People Through Gait
    16.7.4.5.4 Gait Analysis, Depth, 3-D Data, 3-D from Gait
    16.7.4.5.5 Gait Analysis, Diagnosis of Difference, Joint Information, Motion Capture
    16.7.4.5.6 Human Motion Capture, Joint Information, Special Activities
    16.7.4.5.7 Human Motion Capture, Dance Activities

[Saliha]

are these links have software for gait ?????? or just papers etc?? i found nothing from these....

[Walter Roberson]

http://isbweb.org/software/movanal.html

[Image Analyst]

Yeah, you'd think they could of chosen a better name. Of course, maybe that was on purpose.

[Saliha]

still i didn't find any solution :(

will u again suggest any idea by analyzing above picture ???

[Image Analyst]

If imdistline() is too challenging, you can use ginput() and sqrt():

imshow('cameraman.tif');
promptMessage = sprintf('Left-Click on the two points.');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
  return;
end
[x, y] = ginput(2)
distance = sqrt((x(2)-x(1))^2 + (y(2)-y(1))^2)
message = sprintf('The distance is %.3f pixels.', distance);
uiwait(helpdlg(message));

[Saliha]

nice............ and if i want to save these values if multiple points or lines are being computed???

[Saliha]

what about angle ?????

[Saliha]

for multiple lines distances can i use this iteratively ??????????/

[Saliha]

I've done it iteratively but at every iteration values of variables are being replaced.

[Image Analyst]

Use an index:

yourVariable(index) = someValue;

[Saliha]

I'm unable to understand. would you like to elaborate? But i'll try to do it... if not succeeded then i'll consult again.

[Image Analyst]

Show the code for the loop and the array variable you want to set inside it.

[Walter Roberson]

for K = 1 : 10
  [x(K,:) y(K,:)] = ginput(2)
  distance(K) = sqrt((x(K,2)-x(K,1))^2 + (y(K,2)-y(K,1))^2)
  ang(K) = atan2( y(K,2)-y(K,1), x(K,2)-x(K,1) );
  message = sprintf('The distance is %.3f pixels, angle %.3f', distance(K), ang(K));
  uiwait(helpdlg(message));
end

[Saliha]

image analyst..............code is here... at every iteration values of x, y overwrite. i want to save all values.

n=9; 
imshow('img.png');
promptMessage = sprintf('Left-Click on the two points.');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
for i=1:n; 
if strcmpi(button, 'Cancel')
return;
end
[x, y] = ginput(2)
distance = sqrt((x(2)-x(1))^2 + (y(2)-y(1))^2)
message = sprintf('The distance is %.3f pixels.', distance);
uiwait(helpdlg(message)); 
end

[Walter Roberson]

Use what I showed right above, except change "for K = 1 : 10" to "for K = 1 : n".

Note: your strcmpi() test should be before the "for" loop.

[Saliha]

walter roberson ............

this calculates angle from x and y xes. i want to calculate by giving both lines as input.... as shown in above image..... like < ..... this compute at single line

[Walter Roberson]

Whatever. Use the dot product calculation; see http://en.wikipedia.org/wiki/Dot_product

Geometrically, it is the product of the magnitudes of the two vectors and the cosine of the angle between them.

and that tells you that you can find the angle as arccos of the dot product divided by the product of the two magnitudes.

I was more concerned about showing you how to save the values which was the part you were having trouble with.

Note: In order to define the dot product, you need to have a starting point to calculate the distances to the two given points. You do not have that in your code: you only have the two points and you asked to find the distance between those two points; that will go directly from one point to another, not from one point to the branch point to the second point.

[Saliha]

can i use imdistlint with ginput?????? and still need help measuring angle between these drawn two lines.....

[Image Analyst]

imdistline can only handle two points. If you need 3, you can use imline() where you can daisy-chain any number of line segments.

[Saliha]

i want to use ginput() or somethign like this as parameter to imdistline().

and also want to use it Iteratively

[Image Analyst]

Okay, that's fine. ginput() gives giant crosshairs instead of rubber band line, but if that's what you want, that's fine.

[Saliha]

getpts() can b used as input to imdistline() ??????????/

[Saliha]

its good for me to see the code..... if u send as good gesture. I'll be thankful.

[Image Analyst]

I gave code for clicking on points, and Walter gave code for getting angle. Can't you combine them and get something that works? If you can't do that much, how are you going to do the rest of your algorithm, which I'm sure is probably going to be a lot more complicated than that?

[Saliha]

I've combined it . and run it many times. that angle is not calculated as i want. this calculate it from one point only. as getanglefromhorizontal() of imdistline().

[Image Analyst]

Attach your latest code and we might look at it over the weekend if we get time.

[Walter Roberson]

ginput(3) would allow the user to click on one limb, then click on the join at the body, and then click on the other limb; with the points and the order known, calculating the angle becomes a matter of applying the trig formula I gave earlier.

[Saliha]

thanx............. let me try it...

Answer 2

[Usman Siddique]

is u are still working on that project ?

[Walter Roberson]

... after three years?