MATLAB: How to mark the highest white pixel through bottom to the top? using grayscale image.

image acquisitionimage analysisimage processing

   %point location
row=find(sum(img8,2)==0,1,'last')+1;
col=find(img8(row,:)~=0);
row=row(ones(size(col)));
Points=[row(:) col(:)];
imshow(img8);
hold on
plot(Points(:,2),Points(:,1)','rp','MarkerSize',12)
a=text(Points(1,2),Points(1,1),['This is (col,row)(',num2str(Points(1,2)),',',num2str(Points(1,1)),')']);
set(a, 'FontName', 'Arial' ,'FontWeight', 'bold', 'FontSize', 12,'Color', 'blue');
hold off

Best Answer

The white pixels are the ones where all three color components R, G, and B equal 255, so you can get a 2D logical matrix of either white or non-white pixels like this:
I = imread('test.png'); 
white = sum(I,3)==3*255;
The highest white pixel in the image corresponds to the first white pixel in each column, so you can loop through columns going from left to right to find the first white pixel in each column:
row = nan(1,size(white,2)); % preallocates the rows.  
for k = 1:length(row) 
    try
        row(k) = find(white(:,k),1,'first');  
    end
end
imshow(I)
hold on
plot(1:k,row,'b-')
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