how i can find the length*width of an object in an image?

i need to find the size ie, length*width of an object in an image.how can i achieve that?what is the syntax for that?

[Sven]

Can you show us what you mean by "object in an image". Please use example code such as:

I = ... your image
obj = ... your object

Answer 1

[Ramesh kancharapu]

you have to convert your image first in binary (B/W) image then do pixel counting by finding maximum pixel value in row and same in column.

[Image Analyst]

The maximum pixel value (intensity, gray level) won't do any good. You'd have to find the top-most row, bottom most row, left most column and right most column, assuming you have your blob perfectly aligned with the edges of the image. If that's the case, then you can use regionprops

measurements = regionprops(binaryImage, 'BoundingBox');
widths = [measurements.BoundingBox(3)];
heights = [measurements.BoundingBox(4)];

Of course you can also use 'Area' if he wants the area of the blob rather than the size of the bounding box. To find the true longest points on a blob, see attached demo.

[AVINASH SURESHRAO DIKKAR 17MMT1022]

I refered your farthest_point code. I m doing matlab project for inspection of chain link for that i have to find out the object position and measurement. while going through your code i didnt understand how you create boundary around object and create line into that. can you please explaine me and can you explaine me the formula for distance which you use in your code, it will be very helpfull to me and my project.

[Image Analyst]

The x and y coordinates of a blob in a binary image are computed from a function called bwboundaries() like this:

boundaries = bwboundaries(binaryImage);

It's a cell array with each cell having the boundaries for just one of the blobs in the image. Then I loop over all blobs getting the boundary for each individual blob:

thisBoundary = boundaries{blobIndex};
x = thisBoundary(:, 2); % x = columns.
y = thisBoundary(:, 1); % y = rows.

Then you can use sqrt() to find the distance from some particular point

distances = sqrt( (x(k) - x) .^ 2 + (y(k) - y) .^ 2 );

so I do that for every point, to find the distance to every other point. Same thing can be done with pdist2() but you'd need the Statistics and Machine Learning Toolbox to use pdist2(). Not sure how to explain sqrt() to you but the formula is just basically the Euclidean/Pythagorean distance formula for a distance between two points.

[AVINASH SURESHRAO DIKKAR 17MMT1022]

Thank you for your respond and time, i attached images what i want to measure with image processing. i dont want it by freehand object detection. i want to do with automatically code should detect object and give the measurement of height, width and circle diameter. object position may be change its depend on operator thats why i attached 4 images. i tried and after some changes its works to give measurement of object height an width but i failed to measure diameter of circle. can you please help me. i attched code which i made with reference of your code.

[Image Analyst]

Very easy. Just adapt my Image Segmentation Tutorial

Start your own, new thread if you can't do it, since SHRUTHI probably doesn't care about your problem.

You also need better lighting to elimniate shadows. You either need to put it on a lightbox, like what a radiologist uses, or you need to have larger overhead flood illumination.

One thing to try would be a flatbed scanner instead of a camera and small light source.

For utmost accuracy you'd need a telecentric lens.

[AVINASH SURESHRAO DIKKAR 17MMT1022]

I refer your code but it's separating points, not selected single objects. I want to find the diameter of hole which is in object. i know Shruthi doesn't care about my problem but still it is very helpful to me if you tell me solution.

[Image Analyst]

Not sure what you mean by it's separating points, not objects. It definitely gets the coins as objects and does not get individual points (pixels).

I'll give the answer in your own question, like I asked. But I don't see that you've posted it yet. Not sure why you're choosing not to.

Please, if you do like I asked, I would answer.

[AVINASH SURESHRAO DIKKAR 17MMT1022]

Here i attached images and code for what i want to find out. i want to find out height, width and diameter of hole which is in object. i succeed to find out height and also the width which is from from center but i want it maximum width. and fail to find out diameter i tried your image segment code but not work. please see the images and code and give solution on this.

[Eriksson Fejiro]

please can you share how you got the height and width of the object am working on a similar project.. thanks.

Answer 2

[Image Analyst]

Let's say your object looks like an irregular shape - some amorphous blob. What do you define the width and length to be? Can you show us an image of what your blobs look like?