Activity 10 – Preprocessing Text

This activity includes usage of techniques to pre-process an image. Specifically, this is a real-world problem to extract handwritten text from a sample that presents challenges in cleaning object of interest.

The image to the left is the image to be processed. It can be noticed that the image is tilted based from the horizontal lines. Before we process this image, we must rotate it to make horizontal lines horizontal and ease filtering. We used the function mogrify in scilab. The image is tilted at 1.2 degrees. The tilted image is shown at the right.

Next is to crop desired object. I cropped the part where there are horizontal lines, handwritten text and printed text. After cropping, I filtered the horizontal lines in the image using the mask below from its Fourier transform. Then, I binarized the image and apply morphological operations such as opening, closing, erode,dilate and thin. Below are the processed images.

It can be seen from above that after binarizing the image, one can still read the handwritten text VGA Cable and printed text DESCRIPTION. However after applying closing, then thin operations of SE = [1 1]', the one-pixel thick text can't be read. I then chose other handwritten texts to process. Below is another processed images with the same method as above.

Also, I chose a printed text to convince myself that I can digitally extract texts from challenging samples.

I can say that I have extracted the handwritten text DEMO III from above although there is really no rigorous cleaning of the image involved. That is, if I try to clean the image using FT filtering, some parts of my handwritten text can be removed which makes me difficult to read the text after morphological operations. But the printed text, after FT filtering, still can be read. Although some parts or letters are distorted due to filtering of the horizontal lines. Maybe if I can just obtain a good mask and avoid filtering information from the text itself, I may have better results.

Also, correlation is presented in this activity. I used the word DESCRIPTION and try to see if it will produce good correlations in the whole image. The left image is the binarized pattern and to the left is the correlation map. To zoom in, cllick the image. There are white spots that can be noticed in the correlation map. These are the words corresponding to the pattern.

I give myself 9 points for finshing and understanding the activity although I did not get accurately the pre-processing of one pixel handwritten text.