Method and apparatus for decoding bar code symbols using composite signals
First Claim
1. A method for reading a bar code symbol in a pixel image, comprising the steps of:
- (a) selecting a first scan line crossing at least a first portion of said symbol;
(b) transforming said first portion, wherein said transforming comprises the steps of rotating said first portion to an angle substantially parallel to either a row or column of pixels in said image and stretching said first portion;
(c) generating a composite signal in accordance with said transformed first portion;
(d) selecting a second scan line crossing at least a second portion of said symbol;
(e) transforming said second portion, wherein said transforming comprises the steps of rotating said second portion to an angle substantially parallel to either a row or column of pixels in said image and stretching said second portion;
(f) updating said composite signal in accordance with said transformed second portion; and
(g) decoding said symbol in accordance with said composite signal.
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Abstract
A bar code reader decodes a bar code symbol in a pixel image by transforming the data corresponding to the symbol along a first scan line, where the transformation comprises rotation and stretching. The reader generates a composite vector and a count vector from the transformed data. The reader then transforms (by rotating and stretching) another set of data corresponding to the symbol along a second scan line. The reader updates the composite and count vectors using the second set of transformed data. The reader then generates a one-dimensional composite signal from the composite and count vectors. The reader decodes the symbol by decoding the composite signal.
54 Citations
20 Claims
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1. A method for reading a bar code symbol in a pixel image, comprising the steps of:
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(a) selecting a first scan line crossing at least a first portion of said symbol; (b) transforming said first portion, wherein said transforming comprises the steps of rotating said first portion to an angle substantially parallel to either a row or column of pixels in said image and stretching said first portion; (c) generating a composite signal in accordance with said transformed first portion; (d) selecting a second scan line crossing at least a second portion of said symbol; (e) transforming said second portion, wherein said transforming comprises the steps of rotating said second portion to an angle substantially parallel to either a row or column of pixels in said image and stretching said second portion; (f) updating said composite signal in accordance with said transformed second portion; and (g) decoding said symbol in accordance with said composite signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 12)
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9. A method for reading a bar code symbol in a pixel image, comprising the steps of:
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(a) transforming said bar code symbol, wherein said transforming comprises the steps of rotating said bar code symbol to an angle substantially parallel to either a row or column of pixels in said image and stretching said bar code symbol; (b) selecting a first scan line substantially perpendicular to the bars and spaces of said transformed symbol; (c) selecting a second scan line substantially perpendicular to the bars and spaces of said transformed symbol; (d) generating a composite signal, wherein said composite signal is in accordance with said first and second scan lines; and (e) decoding said bar code symbol in accordance with said composite signal, wherein step (d) further comprises the step of calculating the average of a first pixel from said first scan line and a second pixel from said second scan line to yield an element of said composite signal. - View Dependent Claims (10)
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11. An apparatus for reading a bar code symbol in a pixel image, comprising:
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(a) means for selecting a first scan line crossing at least a first portion of said symbol; (b) means for transforming said first portion, wherein said transforming means comprises means for rotating said first portion to an angle substantially parallel to either a row or column of pixels in said image and means for stretching said first portion; (c) means generating a composite signal in accordance with said transformed first portion; (d) means for selecting a second scan line crossing at least a second portion of said symbol; (e) means for transforming said second portion, wherein said transforming means comprises means for rotating said second portion to an angle substantially parallel to either a row or column of pixels in said image and means for stretching said second portion; (f) means for updating said composite signal in accordance with said transformed second portion; and (g) means for decoding said symbol in accordance with said composite signal. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. An apparatus for reading a bar code symbol in a pixel image, comprising:
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(a) means for transforming said bar code symbol, wherein said transforming comprises means for rotating said bar code symbol to an angle substantially parallel to either a row or column of pixels in said image and means for stretching said bar code symbol; (b) means for selecting a first scan line substantially perpendicular to the bars and spaces of said transformed symbol; (c) means for selecting a second scan line substantially perpendicular to the bars and spaces of said transformed symbol; (d) means for generating a composite signal, wherein said composite signal is in accordance with said first and second scan lines; and (e) means for decoding said bar code symbol in accordance with said composite signal, wherein means (d) further comprises means for calculating the average of a first pixel from said first scan line and a second pixel from said second scan line to yield an element of said composite signal. - View Dependent Claims (20)
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Specification