Patent ID: 8781230

Claim:
A method of video-based handwriting input, comprising: capturing an image including effective strokes and digital data of pen pressure, when a user writes on a writing surface with a stylus having a plurality of light sources each with a different color, said image is time-stamped; wherein said plurality of light sources each with a different color includes a light source indicating x-y coordinates of strokes of the stylus and a plurality of other light sources for transmission of digital data of pen pressure on the stylus; wherein the stylus comprises a micro-switch, when the stylus touches the writing surface, the micro-switch is turned on point, and wherein the stylus comprises a micro-controller that compresses and encodes the digital data of pen pressure outputted from an A/D converter from a first number of bits of digital data to a second number of bits of compressed and encoded digital data that is less than the first number of bits and transmits the compressed and encoded digital data of pen pressure as light signals using the plurality of other light sources on the stylus, each of the second number of bits of compressed and encoded digital data corresponding to a different one of the plurality of other light sources on the stylus each with the different color; extracting effective stroke images and the digital data of pen pressure to let the light source indicating x-y coordinates of strokes turn ON and generate a light without performing an initializing step by comparing captured images with a color of the light point of the light source indicating x-y coordinates of strokes of the stylus and each different color of said plurality of other light sources in a transmission of the compressed and encoded digital data of pen pressure; performing mathematical transformation and normalization of the extracted effective stroke images transforming and normalizing the extracted effective stroke images correcting skew of the extracted effective stroke images taken by a camera; and decompressing and decoding the compressed and encoded digital data of pen pressure.