System and method for decoding barcodes not easily perceptible by human vision
A computing device and method for reading a barcode captured with a color image sensor is disclosed. The barcode can have features and background that have equal brightness and a substantially low chromacity deviation such that the barcode could not be easily perceptible and decoded with known greyscale decoding techniques. The method for reading the barcode includes receiving color image values for each pixel of a captured image of a target barcode from a color image sensor, determining chrominance values for each pixel from the color image values, detecting edges based on the chrominance values to generate an edge-detected image that is provided to a greyscale barcode decoder to decode the information in the target barcode. The chrominance values can be based on the blue and red difference components from the YUV image format, and the U and V values can be combined using color temperature information.
1. A method for decoding a target barcode containing information represented by features on a background of the target barcode, the method comprising:
receiving color image values for pixels of a captured image of the target barcode from at least one color image sensor;
determining a chrominance value for pixels of the captured image from the color image values;
detecting edges based on chrominance value to generate an edge-detected image; and
providing the edge-detected image to a greyscale barcode decoder to decode the information in the target barcode,
wherein the features and background of the target barcode have a substantially low chromacity deviation and a similar luminosity.
2. The method of claim 1 , wherein determining chrominance values is based on a function of a blue difference component and a red difference component to emphasize the chromacity deviation of the features from the background.
3. The method of claim 2 , wherein the function is determined by the equation U−rV, where U represents the blue difference component, V represents the red difference component, and r is a constant determined based on color temperature.
4. The method of claim 3 , wherein r is selected as the slope of line perpendicular to a color temperature isotherm.
5. The method of claim 1 , wherein the chromacity deviation and luminosity between the features and background are not easily perceptible by human vision.
6. The method of claim 5 , wherein the chromacity deviation of the feature and background of the target barcode are both within a MacAdam ellipse on a color chart.
7. The method of claim 6 , wherein the chromacity deviation between the features and background are any one of less than 1 nm in the blue-green and yellow wavelengths and less than 10 nm in the red and blue wavelengths.
8. A computing device for decoding a target barcode containing information represented by features on a background, the features and background of the target barcode having a substantially low chromacity deviation and a similar luminosity, the computing device comprising:
at least one color image sensor for providing color image values pixels of a captured image of the target barcode;
a greyscale barcode decoder capable of decoding barcode information from greyscale images;
a memory for storing program code;
a processor coupled to the memory that executes the program code to configure the processor to determine a chrominance value for pixels of the captured image from the color image values, detect edges based on chrominance value to generate an edge-detected image; and provide the edge-detected image to a greyscale barcode decoder to decode the information in the target barcode.
9. The computing device of claim 8 , wherein determining the chrominance values is based on a function of a blue difference component and a red difference component to emphasize the chromacity deviation of the features from the background.
10. The computing device of claim 9 , wherein the function is determined by the equation U−rV, where U represents the blue difference component, V represents the red difference component, and r is a constant determined based on color temperature.
11. The computing device of claim 10 , wherein r is selected as the slope of line perpendicular to a color temperature isotherm.