Calculate from a circle in an image in MATLAB

Hi,

I have to measure the diameter from a circle in a image and I don't quite know where to start.

I began by loading the image and turning it into a blacknwhite image.

img = imread (file);

labimg = rgb2lab(img);

Now I basically need my program to detect the circle and measure the diameter. and then plot it

I really hope someone could help me out

Thanks a lot

[DGM]

Circle measuring aside, you didn't convert your image into black&white. You converted it to L*a*b*. It's still a color image. If you want a grayscale image, you can just use rgb2gray(img) to get the luma. If you want to reduce it to a black & white (binary) image, then you'll need to determine how to best preprocess the image and perform thresholding.

[Rik]

I recovered the removed content from the Google cache (something which anyone can do). Editing away your question is very rude. Someone spent time reading your question, understanding your issue, figuring out the solution, and writing an answer. Now you repay that kindness by ensuring that the next person with a similar question can't benefit from this answer.

Answer 1

[Matt J]

You can use drawcircle() to do it interactively,

https://www.mathworks.com/help/images/ref/drawcircle.html

h = 

  Circle with properties:

      Center: [166.8343 125.4267]
      Radius: 66.4091
       Label: ''
       Color: [0 0.4470 0.7410]
      Parent: [1×1 Axes]
     Visible: on
    Selected: 0