text.how can I find the largest and smallest size letters in a png image and display them in a different color in the image (without deleting other letters)?

how can I find the largest and smallest size letters in the image below and display them in a different color in the image (without deleting other letters)? With the following code, I find the uppercase letter and the lowercase letter, but the other letters are deleted and I can't show them in a different color

BW = imread('text.png');
BW2 = bwpropfilt(BW,'perimeter',1);
figure,imshow(BW2)
BW4=bwareafilt(BW,1,'smallest');
figure, imshow(BW4)

Answer 1

[Walter Roberson]

filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/855240/image.jpeg';
img = imread(filename);
if ndims(img) > 2; gray = rgb2gray(img); else gray = img; end
BW = imbinarize(gray);
BW2 = bwpropfilt(BW,'perimeter',1);

Warning: One or more ties for n-th place occurred when selecting objects. Some objects were not selected.

figure,imshow(BW2)

BW4 = bwareafilt(BW,1,'smallest');

Warning: One or more ties for n-th place occurred when selecting objects. Some objects were not selected.

figure, imshow(BW4)

BW3 = repmat(BW, 1, 1, 3);
BW3(:,:,1) = BW & ~ BW4;
BW3 = im2uint8(BW3);
figure, imshow(BW3)

[betty]

thank you very much, but how can I make the uppercase letter 'm' in color?

[Walter Roberson]

filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/855240/image.jpeg';
img = imread(filename);
if ndims(img) > 2; gray = rgb2gray(img); else gray = img; end
BW = imbinarize(gray);
BW2 = bwpropfilt(BW,'perimeter',1);

Warning: One or more ties for n-th place occurred when selecting objects. Some objects were not selected.

figure,imshow(BW2)

BW4 = bwareafilt(BW,1,'smallest');

Warning: One or more ties for n-th place occurred when selecting objects. Some objects were not selected.

figure, imshow(BW4)

BW3 = repmat(BW, 1, 1, 3);
BW3(:,:,2) = BW & ~ BW2;
BW3(:,:,1) = BW & ~ BW4;
BW3 = im2uint8(BW3);
figure, imshow(BW3)

[betty]

Thank you very much

[DGM]

Just for fun, let's say we wanted to color code all the letters by their size (area).

inpict = imread('text.png'); % a binarized image

N = 256; % length of color table
CT0 = parula(N); % a color table

% get blob areas
S = regionprops(inpict,'area');

% rescale areas to create indices into color table 
area = vertcat(S.Area);
ctidx = round(normalize(area,'range')*(N-1) + 1);

% create augmented CT
CT = [0 0 0; CT0(ctidx,:)];

% get label image, convert to RGB
L = bwlabel(inpict);
outpict = ind2rgb(L+1,CT); % FP-class indexed images are offset by 1

% display it
imshow(outpict)