Method and apparatus for recovering license plate information from an image
First Claim
Patent Images
1. A mobile apparatus, comprising:
- an image sensor configured to capture an optical image including an image of a vehicle license plate; and
a license plate detector configured to;
identify and crop, by a processor, one or more object images from the captured optical image with each of said one or more cropped object images comprising a candidate vehicle license plate image having a plurality of alphanumeric characters,score, by the processor, each of said cropped one or more object images based on a probability that the respective cropped object image comprises the vehicle license plate image, wherein each of the cropped one or more object images is scored by;
providing a rectangular fitting around each character of the plurality of alphanumeric characters,fitting a line to a center of the respective rectangular fittings of each pair of the plurality of alphanumeric characters,for each fitted line, summing a distance of all other respective rectangular fittings to the respective fitted line,selecting the respective pair of alphanumeric characters corresponding to the respective fitted line with a smallest summed distance of all of the fitted lines as a text baseline for the candidate vehicle license plate image,computing a score for the candidate vehicle license plate image having the selected text baseline based at least on the rectangular fitting around each of the alphanumeric characters, relative positions of each of the alphanumeric characters relative to each other within the respective cropped object image and a calculated slope of the fitted line for the selected pair of alphanumeric characters, andrecover, by the processor, information relating to the vehicle license plate inresponse to the calculated score of the candidate vehicle license plate image confirming that the respective cropped object image corresponds to the vehicle license plate.
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Abstract
Some aspects of the invention relate to a mobile apparatus including an image sensor configured to convert an optical image into an electrical signal. The optical image includes an image of a vehicle license plate. The mobile apparatus includes a license plate detector configured to process the electrical signal to recover information from the vehicle license plate image.
645 Citations
29 Claims
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1. A mobile apparatus, comprising:
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an image sensor configured to capture an optical image including an image of a vehicle license plate; and a license plate detector configured to; identify and crop, by a processor, one or more object images from the captured optical image with each of said one or more cropped object images comprising a candidate vehicle license plate image having a plurality of alphanumeric characters, score, by the processor, each of said cropped one or more object images based on a probability that the respective cropped object image comprises the vehicle license plate image, wherein each of the cropped one or more object images is scored by; providing a rectangular fitting around each character of the plurality of alphanumeric characters, fitting a line to a center of the respective rectangular fittings of each pair of the plurality of alphanumeric characters, for each fitted line, summing a distance of all other respective rectangular fittings to the respective fitted line, selecting the respective pair of alphanumeric characters corresponding to the respective fitted line with a smallest summed distance of all of the fitted lines as a text baseline for the candidate vehicle license plate image, computing a score for the candidate vehicle license plate image having the selected text baseline based at least on the rectangular fitting around each of the alphanumeric characters, relative positions of each of the alphanumeric characters relative to each other within the respective cropped object image and a calculated slope of the fitted line for the selected pair of alphanumeric characters, and recover, by the processor, information relating to the vehicle license plate in response to the calculated score of the candidate vehicle license plate image confirming that the respective cropped object image corresponds to the vehicle license plate. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A mobile apparatus, comprising:
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an image sensor configured to capture an optical image, wherein the captured optical image comprises a plurality of object images, and wherein one of the plurality of object images comprises an image of a vehicle license plate; and a license plate detector configured to; identify and crop, by a processor, one or more object images from the captured optical image with each of said one or more cropped object images comprising a candidate vehicle license plate image having a plurality of alphanumeric, score, by the processor, each of said cropped one or more object images based on a probability that the respective cropped object image comprises the vehicle license plate image, wherein each of the cropped one or more object images is scored by; providing a rectangular fitting around each character of the plurality of alphanumeric characters, fitting a line to a center of the respective rectangular fittings of each pair of the plurality of alphanumeric characters, for each fitted line, summing a distance of all other respective rectangular fittings to the respective fitted line, selecting the respective pair of alphanumeric characters corresponding to the respective fitted line with a smallest summed distance of all of the fitted lines as a text baseline for the candidate vehicle license plate image, computing a score for the candidate vehicle license plate image having the selected text baseline based at least on the rectangular fitting around each of the alphanumeric characters, relative positions of each of the alphanumeric characters relative to each other within the respective cropped object image and a calculated slope of the fitted line for the selected pair of alphanumeric characters, and recover, by the processor, information relating to the vehicle license plate in response to the calculated score of the candidate vehicle license plate image confirming that the respective cropped object image corresponds to the vehicle license plate. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A mobile apparatus, comprising:
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an image sensor configured to capture an optical image comprising an image of a vehicle license plate; a display; a rendering module configured to render the captured optical image to the display; an image filter configured to apply one or more filter parameters to the captured optical image based on at least one of color temperature of the image, ambient light, and motion of the apparatus; and a license plate detector configured to; identify and crop, by a processor, one or more object images from the captured optical image with each of said one or more cropped object images comprising a candidate vehicle license plate image having a plurality of alphanumeric characters, score, by the processor, each of said cropped one or more of the object images based on a probability that the respective cropped object image comprises the vehicle license plate image, wherein each of the cropped one or more object images is scored by; providing a rectangular fitting around each character of the plurality of alphanumeric characters, fitting a line to a center of the respective rectangular fittings of each pair of the plurality of alphanumeric characters, for each fitted line, summing a distance of all other respective rectangular fittings to the respective fitted line, selecting the respective pair of alphanumeric characters corresponding to the respective fitted line with a smallest summed distance of all of the fitted lines as a text baseline for the candidate vehicle license plate image, computing a score for the candidate vehicle license plate image having the selected text baseline based at least on the rectangular fitting around each of the alphanumeric characters, relative positions of each of the alphanumeric characters relative to each other within the respective cropped object image and a calculated slope of the fitted line for the selected pair of alphanumeric characters, and recover, by the processor, information relating to the vehicle license plate in response to the calculated score of the candidate vehicle license plate image confirming that the respective cropped object image corresponds to the vehicle license plate; wherein the rendering module is further configured to overlay a detection indicator on the displayed optical image to assist a user in positioning the apparatus with respect to the optical image in response to a signal from the image filter; and wherein the rendering module is further configured to provide an alert to the display when the license plate detector fails to recover the vehicle license plate information. - View Dependent Claims (16)
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17. A computer program product for a mobile apparatus having an image sensor configured to capture an optical image, the captured optical image including a plurality of object images, the computer program product comprising:
a non-transitory machine readable medium comprising code to; select and crop, by a processor, said one of the object images based on the captured optical image, wherein each of said one or more cropped object images comprises a candidate vehicle license plate image having a plurality of alphanumeric characters; provide a rectangular fitting around each character of the plurality of alphanumeric characters; fitting a line to a center of the respective rectangular fittings of each pair of the plurality of alphanumeric characters, for each fitted line, summing a distance of all other respective rectangular fittings to the respective fitted line, selecting the respective pair of alphanumeric characters corresponding to the respective fitted line with a smallest summed distance of all of the fitted lines as a text baseline for the candidate vehicle license plate image, compute a score for the candidate vehicle license plate image having the selected text baseline based at least on the rectangular fitting around each of the alphanumeric characters, relative positions of each of the alphanumeric characters relative to each other within the respective cropped object image and a calculated slope of the fitted line for the selected pair of alphanumeric characters; and recover, by the processor, information relating to a vehicle license plate in response to the calculated score of the candidate vehicle license plate image confirming that the respective cropped object image corresponds to the vehicle license plate. - View Dependent Claims (18, 19, 20, 21, 28, 29)
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22. A mobile apparatus, comprising:
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an image sensor configured to capture an optical image including an image of a vehicle license plate; a timing circuit configured to sample an electrical signal corresponding to the captured optical image at a frame rate; and a license plate detector configured to; identify and crop, by a processor, one or more object images as a candidate vehicle license plate from the captured optical image having a plurality of alphanumeric characters, score, by the processor, each of said cropped one or more of the object images based on a probability that the respective cropped object image comprises the vehicle license plate image, wherein each of the cropped one or more object images is scored by; providing a rectangular fitting around each character of the plurality of alphanumeric characters, fitting a line to a center of the respective rectangular fittings of each pair of the plurality of alphanumeric characters, for each fitted line, summing a distance of all other respective rectangular fittings to the respective fitted line, selecting the respective pair of alphanumeric characters corresponding to the respective fitted line with a smallest summed distance of all of the fitted lines as a text baseline for the candidate vehicle license plate, computing a score for the candidate vehicle license plate having the selected text baseline based at least on the rectangular fitting around each of the alphanumeric characters, relative positions of each of the alphanumeric characters relative to each other within the respective cropped object image and a calculated slope of the fitted line for the selected pair of alphanumeric characters, and recover, by the processor, information relating to the vehicle license plate in response to the calculated score of the candidate vehicle license plate confirming that the respective cropped object image corresponds to the vehicle license plate. - View Dependent Claims (23, 24, 25, 26, 27)
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Specification