Handwritten Hindi Numerals

RecognitionKritika SinghAkarshan Sarkar

Mentor- Prof. Amitabha Mukerjee

Scanned data collection sheet

Building the database

Image obtained after cropping and making the background uniform in color

Preprocessing

Image obtained on doing noise removal followed by binarization

•Noise removal was done using an averaging filter on the grayscale of the original image. •This helps in identifying each numeral as a single connected component.

Building the database

Preprocessing

Bounding box found for each connected component

Building the database

Preprocessing

Images of numerals obtained after resizing and centering

• The cropped images are linearly resized to a matrix of size 40X40• This resized matrix is then centered on a 56X56 matrix of zeros.

Building the database

Preprocessing

Expanding the dataset by blurring and rotating the obtained images

-The samples in the original dataset are deformed to have more variation within a class-This also helps in making the classifier insensitive to intra-class variability -For each numeral obtained, 9 more images are generated by-• Elastic distortion• Rotating each image by two randomly generated angles between 5° to 10° and another two between -5° and -10°

Building the database

Database Expansion

Building the database

Database Expansion

Image after elastic distortion

Before elastic distortion

Building the database

Labeling

• Used k-means clustering for labeling the obtained numerals• 10 clusters were formed for each file and the misclassified numerals in each cluster were manually labeled

Building the database

StatisticsDigit

Number of samples

0 25730

1 42840

2 24940

3 25660

4 15840

5 28160

6 23240

7 4690

8 6010

9 21240

Total size of our database is approximately 200,000 samples

Classification

Feature Extraction

We have used two different feature sets namely-• Projection Histogram Features

• Count the number of foreground pixels in a specified direction

• We created four types of projection histograms – horizontal, vertical, right diagonal and left diagonal

• Chaincode Histogram Features• Edge detection using Canny filter to obtain contour

representation• Further, chaincodes are obtained from this

representation• Image is divided into blocks and local histogram of

these blocks are calculated

Classification

Feature Extraction

Right diagonal histogram Horizontal histogram

Projection histogram

Chain histogram

Contour Representation Chain code Representation

Backpropagation Neural Network

• Used backpropagation algorithm with one hidden layer to train our classifier• Scaled Conjugate Gradient Method was used for backpropagation• This was done using the MATLAB Neural Network Toolbox• 70% of the dataset used as the training set, 15% each for testing and validation.

Results

Projection histogram features

92.2% accuracy on the test set after 112 epochs

Results

Projection histogram features

Results

Chain Code Histogram Features

92.7% accuracy on the test set after 217 epochs

Results

Chain Code Histogram Features

References

[1] Ujjwal Bhattacharya and Bidyut Baran Chaudhuri. Handwritten numeral databases of indian scripts and multistage recognition of mixed numerals. IEEE Trans. Pattern Anal. Mach. Intell., 31(3):444-457, 2009[2] Miguel Po-Hsien Wu, “Handwritten Character Recognition”, The school of Information Technology and Electrical Engineering, The University of Queensland. [3] Bhattacharya, U., Shridhar, M., Parui, S.K.: On recognition of handwritten Bangla characters. In: In: Kalra, P., Peleg, S. (eds.) Proceedings of the 5th Indian Conference on Computer Vision, Graphics and Image Processing (ICVGIP), Springer Lecture Notes on Computer Science, vol 4338, pp. 817–828 (2006)