i have an ultrasound image i want to remove the labeles on the image by using y=mx+b line to convert the pixeles above the line to black.how can i do it?

filename = '181.png';
img= imread(filename);
gray = im2gray(img);

for i=1:434
    for j=1:634
        if(j < (0.77i+235))
            img(i,j) = 255;
        else
            img(i,j)=0;
        end
    end
end

subplot(2,2,1), imshow(img),title('transformed image');

[hume]

thank you so much you sae my day!

Answer 1

[DGM]

There are a couple things going on here.

filename = '181.png';
img = imread(filename);
img = im2gray(img); % need to work on the right image

% use the actual image dimensions
[nrows,ncols,~] = size(img);
for row = 1:nrows
    for col = 1:ncols
        % image origin is NW corner, so a line which points from SW to NE
        % actually has negative slope!
        if row < (-0.77*col + 240)
            img(row,col) = 128; % i'm using gray so it's easy to see 
        end
    end
end

imshow(img)

This could also be done without the loops

filename = '181.png';
img = imread(filename);
img = im2gray(img); % need to work on the right image

[nrows,ncols,~] = size(img);
R = 1:nrows;
C = 1:ncols;
mask = R.' < (-0.77*C + 240);
img(mask) = 128;

imshow(img)

Alternatively, you could use a polygon mask to perform the selection. See drawpolygon() and createMask().