| 摘要 |
Bit data is encoded into characters in an input image by providing different darkness levels for pixels in either half of a text character. To determine if the input image is of a right-side up document, or an upside-down document, multiple scans of the input image at 90° rotations between scans may be made. Each scan result is searched for occurrences of a indicator prefix bit-sequence. The scan that contains the indicator prefix bit-sequence is elected as the right-side up orientation for the input image. If multiple scans show occurrences of the indicator prefix bit-sequence, then the scan that has the highest number of occurrences is elected as the correct orientation. Alternatively, the number of data bits between repeated occurrences of the indicator prefix bit-sequence is compared with a predefined message bit size, and the scan that matches most closely is elected as the correct orientation.
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