Character Recognition Example (II):Automating Image Pre-processing

Most of the time we would like to automate our image pre-processing stage especially during the data extraction for database. In other words, the program should be able to extract the characters one by obe and map the target output for training purpose. The following code shows the example:

1. Read Image
This cell of codes read the image to MATLAB workspace

I = imread('sample.bmp');
imshow(I)

2. Convert to grayscale image
This cell of codes convert the RGB to gray

Igray = rgb2gray(I);
imshow(Igray)


3. Convert to binary image
This cell of codes convert the gray to binary image

Ibw = im2bw(Igray,graythresh(Igray));
imshow(Ibw)


4. Edge detection
This cell of codes detect the edge of the image

Iedge = edge(uint8(Ibw));
imshow(Iedge)

5. Morphology
This cell of codes perform the image dilation and image filling on the image

Image Dilation

se = strel('square',2);
Iedge2 = imdilate(Iedge, se);
imshow(Iedge2);


Image Filling

Ifill= imfill(Iedge2,'holes');
imshow(Ifill)


6. Blobs analysis
This cell of codes find all the objects on the image, and find the properties of each object.

[Ilabel num] = bwlabel(Ifill);
disp(num);
Iprops = regionprops(Ilabel);
Ibox = [Iprops.BoundingBox];
Ibox = reshape(Ibox,[4 50]);
imshow(I)

50


7. Plot the Object Location
This cell of codes plot the object locations

hold on;
for cnt = 1:50
rectangle('position',Ibox(:,cnt),'edgecolor','r');
end


By this, we are able to extract the character and pass to another stage for "classification" or "training" purpose. (To be continue...)

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The required files can be found at:
(link for the required files will be provided soon...)