Detect letters in an image

Hey!

I have a text image from where I want to detect the letters 'y' by:

• select one morphological operation for the purpose
• design the corresponding structuring element
• apply the filter to the image once
• calculate the skeleton of the detected letter

And I really have no idea how can I do this. Can someone please help? The input image is 'text.png' from matlab

Thank you in advance!

Answer 1

[Rishabh Singh]

Hey,

You can refer to this, or you can run the code below.

clear all

close all

% Read in image

I = imread('textsample.png');

I = rgb2gray(I);

% Have user select a section of the image and create template

a_template = imcrop(I);

figure

imshow(a_template)

% Cross-correlate the image with the template

Xcorr = normxcorr2(a_template, I);

% Threshold the image

t_Xcorr = graythresh(Xcorr);

Xcorr_threshold = Xcorr > 0.7;

figure

imshow(Xcorr_threshold);

% Dim of the template and image are needed for drawing boxes and loops

temp_dim = size(a_template);

I_dim = size(I);

y_len = temp_dim(1); x_len = temp_dim(2);

% Find the blods in the thresholded image

L = bwlabel(Xcorr_threshold);

blobs = regionprops(L);

% Draw red box around all the centroids of the blobs

figure

imshow(I)

for k = 1:length(blobs)

y1 = blobs(k).Centroid(2) - y_len/2; x1 = blobs(k).Centroid(1) - x_len/2;

pos_vec = [x1-x_len/2 y1-y_len/2 temp_dim(2) temp_dim(1)];

rectangle('Position', pos_vec, 'EdgeColor', 'r');

drawnow;

end

% Display the number of a's

text(175,100, "There are: " + length(blobs) + " a's", 'FontSize', 14, 'color', 'r')

Also refer to documentation for more help and also checkout "bwmorph".