having difficulty in simple circle detection

Hi,

I am having difficulty finding a circle.

I already tried 'imfindcirles' , with different sensitivity but failed.

please help in this. i want to find the radius and center point of the dark blue circel (image attached).

Thanks in advance.

Answer 1

[Image Analyst]

Use the Color Thresholder app on the apps tab of the tool ribbon. I'd use hsv color space. Then adjust the thresholds and Export the code into a new function m-file.

rgbImage = imread('Captur11.jpg');
subplot(2, 1, 1);
imshow(rgbImage);
[BW,maskedRGBImage] = createMask(rgbImage);
% Fill holes
BW = imfill(BW, 'holes');
% Take largest blob.
BW = bwareafilt(BW, 1);
subplot(2, 1, 2);
imshow(BW)

function [BW,maskedRGBImage] = createMask(RGB)
%createMask  Threshold RGB image using auto-generated code from colorThresholder app.
%  [BW,MASKEDRGBIMAGE] = createMask(RGB) thresholds image RGB using
%  auto-generated code from the colorThresholder app. The colorspace and
%  range for each channel of the colorspace were set within the app. The
%  segmentation mask is returned in BW, and a composite of the mask and
%  original RGB images is returned in maskedRGBImage.

% Auto-generated by colorThresholder app on 11-May-2020
%------------------------------------------------------

% Convert RGB image to chosen color space
I = rgb2hsv(RGB);

% Define thresholds for channel 1 based on histogram settings
channel1Min = 0.584;
channel1Max = 0.619;

% Define thresholds for channel 2 based on histogram settings
channel2Min = 0.856;
channel2Max = 1.000;

% Define thresholds for channel 3 based on histogram settings
channel3Min = 0.000;
channel3Max = 1.000;

% Create mask based on chosen histogram thresholds
sliderBW = (I(:,:,1) >= channel1Min ) & (I(:,:,1) <= channel1Max) & ...
	(I(:,:,2) >= channel2Min ) & (I(:,:,2) <= channel2Max) & ...
	(I(:,:,3) >= channel3Min ) & (I(:,:,3) <= channel3Max);
BW = sliderBW;

% Initialize output masked image based on input image.
maskedRGBImage = RGB;

% Set background pixels where BW is false to zero.
maskedRGBImage(repmat(~BW,[1 1 3])) = 0;
end

[Abhilash Uniyal]

yeah thanks,I think it will work but ,

sorry, I think, i wasnt clear in my question.

once we get the RGB values, i want center points(x, y cordinates) and radius of this circle.

Thanks,

Abhishek

[Image Analyst]

Try this:

props = regionprops(BW, 'Centroid', 'EquivDiameter');
radius = props.EquivDiameter / 2;
xCenter = props.Centroid(1);
yCenter = props.Centroid(2);
[r, g, b] = imsplit(rgbImage);
meanR = mean(r(BW))
meanG = mean(g(BW))
meanB = mean(b(BW))

[Abhilash Uniyal]

Thank you, It worked :)