Generating copybooks from consistent handwriting styles

Ralph Niels & Louis VuurpijlNijmegen Institute for Cognition and Information

Radboud University NijmegenThe Netherlands

Overview

Handwriting styles and copybooks Method Results Discussion

Handwriting styles

Handwriting is individual Similar handwritings: handwriting

styles Top down ‘copybooks’ * We defined writing styles bottom up

* S.-H. Cha, S. Yoon, C.C. Tappert, 2006.

Applications

Handwriting recognition Personalized recognizers

Handwriting synthesis ‘Handwriting fonts’

Forensic writer identification Human experts use the notion of style

K. Franke, 2005

Method (1)DataData

Data

Databases: Unipen trainset Unipen devset Plucoll database

Online handwritten characters(pre-segmented)

43 writers

41 writers

Method (2)Data

Clustering of prototypes The prototype we used are averaged

shapes of actual handwritten characters

L. Vuurpijl & L. Schomaker, Finding Structure in Diversity, ICDAR 1997.R. Niels, L. Vuurpijl & L. Schomaker, Automatic allograph matching inforensic writer identification, IJPRAI, Feb. 2007.

Clustering of prototypes

PCj

PCk

PCi

Prototypes

Prototype clusters

Method (3)Data

Create membership vectors

Relative frequency of the occurrence of each prototype cluster in a persons handwriting

0

0,1

0,2

0,3

0,4

0,5

0,6

Writer X

PC 1PC 2PC 3PC 4PC 5

Create membership vectors(example: handwriting X)

PCj

PCk

PCi

Prototypes

Prototype clusters

0.15

0.05

0.05

0.52

0.23

0.2

0.8

1.0

Create membership vectors(example: handwriting X, Y and Z)

0

0,1

0,2

0,3

0,4

0,5

0,6

X Y Z

Handwriting Z 0.12

0.01

0.22

0.55

0.10

Handwriting X 0.15

0.05

0.05

0.52

0.23

Handwriting Y 0.47

0.41

0.00

0.09

0.03

Method (4)Data

Find writing styles Hierarchical clustering of

membership vectors (handwritings)

H Z X E D I A GB B J K Y C FHandwriting

Writingstyles

Method (5)Data

PCj

PCk

PCi

H Z X E D I A GB B J K Y C F

Select consistent handwriting styles

Cluster parameters

Cluster parameters

Level selection

Level selection

Monte Carlo simulation of combinations of parameters and levels

Large number of writing styles Find the writing styles that occur

most By prototypes or By writers

Select consistent handwriting styles

Results

Copybooks Preliminary results Visual evaluation by handwriting

experts Meaningful names Well-known broad categories:

cursive, mixed and print

Results (example handwritings)

Mixed

Cursive

Print

Results (prototype occurrence)

Mixed

Cursive

Print

Discussion Applied to/with, not limited to:

Online Latin characters Dynamic Time Warping for

character comparison (human congruous)

Best of both worlds: Integrate top down and bottom up (with forensic experts)

H Z X E D I A GB B J K Y C F

Integrate

Questions?