Loop Investigation for Cursive Handwriting Processing and Recognition

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Loop Investigation for Cursive Handwriting Processing and Recognition. By Tal Steinherz Advanced Seminar (Spring 05). Outline. Background on cursive handwriting. Introduction to loops. Pattern recognition and machine learning conflicts. Feature extraction solutions. - PowerPoint PPT Presentation

Transcript of Loop Investigation for Cursive Handwriting Processing and Recognition

  • Loop Investigation for Cursive Handwriting Processing and RecognitionBy Tal Steinherz

    Advanced Seminar (Spring 05)

  • OutlineBackground on cursive handwriting

    Introduction to loopsPattern recognition and machine learning conflictsFeature extraction solutionsDemonstrations and experimental results

  • Cursive Handwriting (J. C. Simon)Displacing a pen from left to right in an oscillating movement, with loops, descendants (legs), and ascendants (poles).

  • Cursive vs. CharacterCursive continuous concatenated set of strokes. produced by a human being in a free style.Character a single standalone symbol. produced by a machine subjected to numerous alternative fonts.

  • Online vs. OfflineOnline captured by pen-like devices. the input format is a two-dimensional signal of pixel locations as a function of time (x(t),y(t)).Offline captured by scanning devices. the input format is a two-dimensional image of gray-scale colors as a function of location I(m*n). strokes have significant width.

  • Online vs. Offline (demo)

  • A Loop (T. Steinherz)A set of neighboring foreground pixels surrounding a hole, i.e., a connected blocked group of background pixels in the words image, where all foreground pixels are within stroke width distance from the hole.

  • Ascending (Descending) Loops

  • Axial (of the middle zone) Loops

  • The importance of loops Shared by many letters (especially a,d,e,g,o,p,q)Byproduct of the continuous nature of cursive handwriting (like with b,f,h,j,k,l,s,t,y,z)Elementary and prominent featuresCarry additional information given by a set of descriptive parameters

  • The motivation to investigate loopsCharacter recognition supports discrimination between letters.Writer modelingIdentificationExaminationcontributes to applications in forensic science and graphology.

  • The output of loop investigationIncomplete (open) loop identificationHidden (collapsed) loop tracking - locating blobs that correspond to online loopsMulti (encapsulated) loops understanding - distinguishing natural from artificial loopsTemporal information recovery - retracing the original path of a pen

  • The Engineering Approach(J. C. Simon & T. Pavlidis)Requires understanding the structure of the objects to be recognized and apply the appropriate combination of (pattern recognition) techniques.

  • Feature extraction dilemmasOffline cursive word signal representationLoop identificationSignal to noise ratioFeature vector translation

    The difficulties consist in the feature extraction and preprocessing rather than the machine learning \ recognition engine phase.

  • Offline cursive word signal representationWe use the external upper and lower contours in conjunction with the internal contour of all visible loops.

  • Loop identificationGiven a set of singular points, identification is provided by correlation between pieces of the same contour (around anchor points), of the opposite contours and\or in association with subsets of internal contours.

  • Signal to noise ratioIn order to improve the signals parametric quantifiability and reduce noisy artifacts, the contour is transformed to a polygon.

  • Hidden loop tracking -the mutual distance principle

  • Hidden loop tracking -the mutual distance principle (cont.)

  • Hidden loop tracking -the mutual distance principle (cont.)

  • Multi loops understanding -the continuity principle

  • Temporal information recovery -the matching principle

  • Hidden loop tracking -an application to ascending (descending) loops

  • Hidden loop tracking -an application to ascending (descending) loops (cont.)

  • Hidden loop tracking -an application to ascending (descending) loops (cont.)

  • Hidden loop tracking -an application to ascending (descending) loops (cont.)ThresholdSmall LoopsNo LoopsTotal81802093896131209340

  • Multi loops understanding -a classifier of beginning a-sMore than 40 writers with 1-4 samples per writer.

  • Multi loops understanding -a classifier of beginning a-s