calculating error while averaging multiple images

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Sumera Yamin 2020-7-30

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https://ww2.mathworks.cn/matlabcentral/answers/572626-calculating-error-while-averaging-multiple-images

评论： Image Analyst 2020-8-17

Hi, I have a simple problem and needs guidance. I have 15 image files. I want to calculate the average of these images and calculate error on these images. Any help is appreciated.

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Walter Roberson 2020-8-9

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https://ww2.mathworks.cn/matlabcentral/answers/572626-calculating-error-while-averaging-multiple-images#answer_477136

Do you want the average of the R, G, and B separately for each image?

Are you asking for averages to be taken over time for each pixel's R, G, B components?

Read the images into a 4D array, rows by columns by colorpanes by image_number . Then mean(Stack,4) or std(Stack, [], 4)

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Walter Roberson 2020-8-12

function [imageData, imgstd] = meanImage(path, fileNamePrefix, fileNameSufix, n, mStart, mEnd)
    N = mEnd - (mStart - 1);
    currentImage = double(loadImage(path, fileNamePrefix, fileNameSufix, n, mStart));
    imgsum = currentImage;
    imgsqsum = imgsum.^2;
    
    for mm = (mStart+1):mEnd
        currentImage = double(loadImage(path, fileNamePrefix, fileNameSufix, n, mm));
        imgsum = imgsum + currentImage;
        imgsqsum = imgsqum + currentImage.^2;
    end
    mean_img = imgsum ./ N;
    imageData = cast(mean_img, class(currentImage));
    imgstd = sqrt((imgsqsum - 2 .* mean_img .* imgsum + mean_img.^2) ./ (N-1));
end

This code deliberately turns the mean image back into the datatype of the individual images, such as uint8. This is because it calculates the mean image in the same units as the original image, not in terms of the 0 to 1 range that could be used instead. Whether this is best for you depends on what you want to do with the mean image.

Sumera Yamin 2020-8-12

so i took this part of code and did the furthur processing of my data. combining with the above function, the code is as shown below. The problem is that for i want to use both imageData and imgstd for calculating [maxzeile, maxspalte] and [maxzeile_err, maxspalte_err] respectively. My code however takes imageData for calculating both and hence giving me the same output. Could you please pointout how should i change the code to use both imagedata and imgstd.

function [maxzeile, maxspalte, maxzeile_err, maxspalte_err, xRMS, yRMS] = findBeam(beamIn, windowsize, threshold, maxIterations)
%rough beam position
BEAMFOUND = 0;
WINDOWSIZE = windowsize/2;
THRESHOLD = round(threshold*WINDOWSIZE^2);
n = 0;
beamImageSize = size(beamIn);
while (BEAMFOUND == 0 && n <= maxIterations)
	[maxwerte, maxzeilen] = max(beamIn); 
	[maxwert, maxspalte] = max(maxwerte);
	maxzeile = maxzeilen(maxspalte);
   if (maxzeile <= WINDOWSIZE)
      yLow = 1;
   else
      yLow = maxzeile-WINDOWSIZE;
   end
   if (maxzeile + WINDOWSIZE >= beamImageSize(1))
      yHigh = beamImageSize(1);
   else
      yHigh = maxzeile+WINDOWSIZE;
   end
   if (maxspalte <= WINDOWSIZE)
      xLow = 1;
   else
      xLow = maxspalte-WINDOWSIZE;
   end
   if (maxspalte + WINDOWSIZE >= beamImageSize(2))
      xHigh = beamImageSize(2);
   else
      xHigh = maxspalte+WINDOWSIZE;
   end
   yLow = abs(round(yLow)); %disp(yLow)
   yHigh = abs(round(yHigh)); %disp(yHigh)
   xLow = abs(round(xLow)); %disp(xLow)
   xHigh = abs(round(xHigh)); %disp(xHigh)
   %disp('------')
   
   window = beamIn(yLow:yHigh,xLow:xHigh); %figure(n+5); imagesc(window);
    
   % Intensity cut
   thre = 0.75 * max(max(window));
   beamArea = sum(sum(window>thre));
   if (beamArea >= THRESHOLD)
		BEAMFOUND = 1;
   else
	beamIn(yLow:yHigh,xLow:xHigh) = 0; %beamIn(yLow:yHigh,xLow:xHigh)>10000;
   end
   n = n + 1;
end
[xRMS, yRMS] = beamRMS(window);
   beamImageSize = size(beamIn(yLow:yHigh,xLow:xHigh));
   beamX = 1:beamImageSize(2);
   beamY = 1:beamImageSize(1);
   totalMass = sum(sum(beamIn(yLow:yHigh,xLow:xHigh)));
   centerOfMass = zeros(1,2);
   for i=1:length(beamX)
      for  j=1:length(beamY)
      	centerOfMass = centerOfMass + double(window(j,i)).*double([beamY(j),beamX(i)]);
      end
   end
   centerOfMass = centerOfMass / totalMass;
   centerOfMass = round(centerOfMass);
   centerOfMass = centerOfMass + [yLow,xLow];
     maxzeile = centerOfMass(1);
   maxspalte = centerOfMass(2);
%error in center of mass:
   beamImageSize_err = size(beamIn(yLow:yHigh,xLow:xHigh));
   beamX_err = 1:beamImageSize_err(2);
   beamY_err = 1:beamImageSize_err(1);
   totalMass_err = sum(sum(beamIn(yLow:yHigh,xLow:xHigh)));
   centerOfMass_err = zeros(1,2);
   for i=1:length(beamX_err)
      for  j=1:length(beamY_err)
      	centerOfMass_err = centerOfMass_err + double(window(j,i)).*double([beamY_err(j),beamX_err(i)]);
      end
   end
   centerOfMass_err = centerOfMass_err / totalMass_err;
   centerOfMass_err = round(centerOfMass_err);
   centerOfMass_err = centerOfMass_err + [yLow,xLow];
   maxzeile_err = centerOfMass_err(1);
   maxspalte_err = centerOfMass_err(2);
end