Watermarking of text images using character step edge adjustment
Linlin Li · Journal of Computer Applications · 2008
A novel feature calibration watermarking for binary text document images was proposed. Good imperceptibility could be achieved by adjusting the character step edge stroke instead of horizontal and vertical stroke. With this principle, the adjustment method could be applied to change the summation ratio of black pixels between the upper half part and the lower half part of each line text image. Higher and lower ratio express watermark bit 0 and bit 1 separately. Extracting watermark from the watermarked text images just depended on the result of the detected ratio compared to the given thresholds. The experiments were performed with Chinese and English binary text document images. It reveals that this text watermarking has good imperceptibility and robustness against various operations and attacks, such as scaling, nosing, cropping, multi-times printing and scanning.