MATLAB: Direct Sun Detector code

image processingImage Processing Toolboxsuntime lapse photography

Dear All;
I have camera fixed in my office which capture image every 5 minute and the captured image sent to MATLAB, what is the best code to detect sun rays that passes through window?
if there is sun rays in office display ('direct sun') else display ('no direct sun')

Best Answer

I'd take an image with the sun in view and then find out how bright it is and it's size. Then threshold the image and look for items roughly that bright and that size. 
grayImage = rgb2gray(rgbImage);
binaryImage = grayImage > someValue; % someValue is some value that the sun is ALWAYS brighter than.
[labeledImage, numBlobs] = bwlabel(binaryImage);
props = regionprops(binaryImage, 'Area');
allAreas = [props.Area]
sunBlobs = allAreas >= minAreaForSun & allAreas <= maxAreaForSun;
if sum(sunBlobs) >= 1
    % There is a sun in the image.
    fprintf('Direct Sun at %s\n', datestr(now));
else
    % There is no sun in the image.
    fprintf('No Direct Sun at %s\n', datestr(now));
end
Attach photos of "with sun" and "without sun" if you need more help.
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