How to extract a digit from an image?

Hey there,

i have this not so much working code that i wrote on how to extract the 2 numbers that appear on the image into 2 diffrent images containing only 1 digit each, the code i wrote is very inconsistent and not always working, if thers someone who can maybe send me their code or help me improve mine would be wonderfull.. thanks!!

%%

Speed = rgb2grey(speed2);
 
binSpeed = im2bw(Speed, 0.4);       %%making the pic a binary image


%% identifying digit number 1
it = 0;
sz = size(Speed, 2);
   for k=2:sz-1
if (sum(binSpeed(:,k) == 0) > 0) && (sum(binSpeed(:,k-1) == 0) == 0)        %% checking the index value of the start of the digit
    dig = k+1;        %% in case the if was true, assembeling the index to dig

end

if (sum(binSpeed(:,k) == 0) > 5) && (sum(binSpeed(:,k+1) == 0) < 7)        %% checking the index value of the end of the digit       
    it = k+1;     %% in case the if was true, assembeling the index to it

end

if (it ~= 0)        %% stopping the for loop so that the indexes of the digits wont change
    break
end
   end
   
digit1 = binSpeed( :, (dig:it));

%% identifying digit number 2
it2 = 0;
   for g=it+1:sz-1
if (sum(binSpeed(:,g) == 0) > 0) && (sum(binSpeed(:,g-1) == 0) == 0)        %% checking the index value of the start of the digit
    dig2 = g;        %% in case the if was true, assembeling the index to dig

end

if (sum(binSpeed(:,g) == 0) > 5) && (sum(binSpeed(:,g+1) == 0) < 7)        %% checking the index value of the end of the digit       
    it2 = g;     %% in case the if was true, assembeling the index to it

end

if (it2 ~= 0)        %% stopping the for loop so that the indexes of the digits wont change
    break
end
   end

digit2 = binSpeed( :, (dig2:it2));


 %% cutting the first digit
 
 sz2 = size(digit1, 1);
 
for ik=2:sz2-1
    if(sum(digit1(ik,:) == 0) > 0) && (sum(digit1(ik-1,:) == 0) == 0)
        st = ik;
    end
    if(sum(digit1(ik,:) == 0) > 2) && (sum(digit1(ik+1,:) == 1) > 2)
        nd = ik;
    end
end

digit1 = digit1((st:nd), :);

%% cutting the second digit

sz3 = size(digit2, 1);

for s=2:sz3-1
    if(sum(digit2(s,:) == 0) > 0) && (sum(digit2(s-1,:) == 0) == 0)
        st2 = s;
    end
    if(sum(digit2(s,:) == 0) > 5) && (sum(digit2(s+1,:) == 1) > 10)
        nd2 = s;
    end
end

digit2 = digit2((st2:nd2), :);

Answer 1

[Image Analyst]

Try using regionprops() to get each digits bounding box, then use imcrop to extract it into its own image:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 22;

%--------------------------------------------------------------------------------------------------------
%    READ IN IMAGE
folder = pwd;
baseFileName = 'Speed2.jpg';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
	% The file doesn't exist -- didn't find it there in that folder.
	% Check the entire search path (other folders) for the file by stripping off the folder.
	fullFileNameOnSearchPath = baseFileName; % No path this time.
	if ~exist(fullFileNameOnSearchPath, 'file')
		% Still didn't find it.  Alert user.
		errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
		uiwait(warndlg(errorMessage));
		return;
	end
end
% Get the dimensions of the image.
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(grayImage);
if numberOfColorChannels > 1
	% It's not really gray scale like we expected - it's color.
	% Use weighted sum of ALL channels to create a gray scale image.
	grayImage = rgb2gray(grayImage);
	% ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
	% which in a typical snapshot will be the least noisy channel.
	% grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the image.
hFig = figure;
subplot(2, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize, 'Interpreter', 'None');
impixelinfo;
hFig.WindowState = 'maximized'; % May not work in earlier versions of MATLAB.
drawnow;

%--------------------------------------------------------------------------------------------------------
%    SEGMENTATION
% Binarize the image
binaryImage = ~imbinarize(grayImage);
% Take the largest 2 blobs only.
binaryImage = bwareafilt(binaryImage, 2);
% Display the segmented image.
subplot(2, 2, 2);
imshow(binaryImage, []);
title('Binary Image', 'FontSize', fontSize, 'Interpreter', 'None');
axis('on', 'image');

%--------------------------------------------------------------------------------------------------------
%    EXTRACTION OF EACH BLOB
props = regionprops(binaryImage, 'BoundingBox');
% Display them
for k = 1 : length(props)
	thisBB = props(k).BoundingBox;
	croppedImage{k} = imcrop(binaryImage, thisBB);
	subplot(2, 2, k+2);
	imshow(croppedImage{k});
	caption = sprintf('Digit #%d', k);
	title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
end

[Shoval Matzner]

omg thank you so much!!

is there a way to not do it as a plot because i need to then run some MSE algorythems on it and i dont really know how to use it when its a plot

[Image Analyst]

I don't know what it means to "plot" an image. Please explain. I only know how to "display" an image. If you don't want to display, then don't call imshow(). Please post something that shows what you want.

[Shoval Matzner]

% Display the image.
hFig = figure;
subplot(2, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize, 'Interpreter', 'None');
impixelinfo;
hFig.WindowState = 'maximized'; % May not work in earlier versions of MATLAB.
drawnow;

you displayed the pic as a sub plot as its shown here, is there a way to leave the image as a matrix and not displaying it as a subplot

subplot(2, 2, k+2);
	imshow(croppedImage{k});
	caption = sprintf('Digit #%d', k);
	title(caption, 'FontSize', fontSize, 'Interpreter', 'None');

[Image Analyst]

Of course. Just cut out any lines like the second group of 4 lines you posted in your above comment. You know what subplot(), imshow(), sprintf(), and title() do, don't you? If you don't want them then don't call them. If that solves your question, could you "Accept this answer"? Thanks in advance.

[Shoval Matzner]

yes, thank you so much for your help!! you da real mvp