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# Algorithm to Capture Handwriting on a Tablet

IP.com Disclosure Number: IPCOM000060705D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

IBM

Helms, R: AUTHOR

## Abstract

An algorithm is described to capture handwriting on an electronic tablet. The algorithm succeeds in capturing the handwritten image from the tablet, updating a corresponding image in memory. One problem that is solved is keeping up with the user's speed to capture sufficient points to produce a smooth line, avoiding choppiness due to low frequency sampling. Two modes are used to do this. Mode 1 ŒSTART: Check tablet till pen down Œ If first point in a line save location - else draw a line to previous point Œ Go to START While most simple and very easy to implement, this causes a low sampling of the tablet and can result in a choppy line.

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Algorithm to Capture Handwriting on a Tablet

An algorithm is described to capture handwriting on an electronic tablet. The algorithm succeeds in capturing the handwritten image from the tablet, updating a corresponding image in memory. One problem that is solved is keeping up with the user's speed to capture sufficient points to produce a smooth line, avoiding choppiness due to low frequency sampling. Two modes are used to do this. Mode 1 OESTART: Check tablet till pen down OE If first point in a line save location - else draw a line to previous point OE

Go to START While most simple and very easy to implement, this causes a low sampling of the tablet and can result in a choppy line. Mode 2 OESTART2: Check if pen on tablet is down OE If pen is down then: - Capture point - If buffer full handle as in mode 1 above: Go to START2 - Save point in buffer - Go to START2 OE Else - Retrieve last point from buffer - If first point then save else draw line to last point OE Go to START2 To avoid the time it can take to draw long lines, the draw routine can sample check the tablet and exit to the sample routine when the pen is sensed as being on the surface. If the tablet can be set on an interrupt, then sampling can be done to the same circular buffer, while a separate routine can be servicing the buffer.

(Image Omitted)

OE A point is placed in the NEXT AVAILABLE SLOT, and the pointer is incremented by 1. OE If NEXT AVAILABLE SLOT = END, then it reverts to START. OE If NEXT...