SYSTEM FOR CAPTURING A DOCUMENT IN AN IMAGE SIGNAL

• US 20110285873A1
• Filed: 01/28/2011
• Published: 11/24/2011
• Est. Priority Date: 05/21/2010
• Status: Active Grant

• Current Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Original Assignee: Hand Held Products Incorporated (Honeywell International Inc.)
• Inventors: Showering, Paul Edward
• Granted Patent: US 8,600,167 B2
• Time in Patent Office: Days
• US Class Current: 348/231.99
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/142 using hand-held instruments; Constructional details of the instruments
• CPC Class Codes: G06V 30/1475 Inclination or skew detection or correction of characters or of image to be recognised
• CPC Class Codes: G06V 30/1607 Correcting image deformation, e.g. trapezoidal deformation caused by perspective
• CPC Class Codes: G06V 30/18076 by analysing connectivity, e.g. edge linking, connected component analysis or slices
• CPC Class Codes: H04N 23/00 Cameras or camera modules comprising electronic image sensors; Control thereof
• CPC Class Codes: H04N 5/772 the recording apparatus and the television camera being placed in the same enclosure

Abstract

Devices, methods, and software are disclosed for capturing a frame of image data having a representation of a feature. In an illustrative embodiment, a device includes an imaging subsystem, one or more memory components, and a processor. The imaging subsystem is capable of providing image data representative of light incident on said imaging subsystem. The one or more memory components include at least a first memory component operatively capable of storing an input frame of the image data. The processor is in communicative connection with executable instructions for enabling the processor for various steps. One step includes receiving the input frame from the first memory component. Another step includes generating a reduced resolution frame based on the input frame, the reduced resolution frame comprising fewer pixels than the input frame, in which a pixel in the reduced resolution frame combines information from two or more pixels in the input frame. Another step includes attempting to identify transition pairs comprising pairs of adjacent pixels in the reduced resolution frame having differences between the pixels that exceed a pixel transition threshold. Another step includes attempting to identify one or more linear features between two or more identified transition pairs in the reduced resolution frame. Another step includes providing an indication of one or more identified linear features in the reduced resolution frame.

Claims

1. A device comprising:

an imaging subsystem capable of providing image data representative of light incident on said imaging subsystem;

one or more memory components, comprising at least a first memory component operatively capable of storing an input frame of the image data; and

a processor, enabled for;

receiving the input frame from the first memory component;

generating a reduced resolution frame based on the input frame, the reduced resolution frame comprising fewer pixels than the input frame, in which a pixel in the reduced resolution frame combines information from two or more pixels in the input frame;

attempting to identify transition pairs comprising pairs of adjacent pixels in the reduced resolution frame having differences between the pixels that exceed a pixel transition threshold;

attempting to identify one or more linear features between two or more identified transition pairs in the reduced resolution frame; and

providing an indication of one or more identified linear features in the reduced resolution frame.

2. The device of claim 1, in which the processor is further enabled such that generating the reduced resolution frame further comprises sectioning the input frame into groups of pixels, and for each of the groups of pixels, averaging one or more properties of the pixels in the group of pixels and generating an averaged pixel having the averaged properties of the group of pixels.

3. The device of claim 2, in which the processor is further enabled such that generating the reduced resolution frame further comprises sectioning the input frame into first-stage groups of four pixels per group in a 2×

2 arrangement and generating a first-stage reduced pixel having the averaged properties of the first-stage group of pixels, thereby generating a first-stage reduced resolution frame;

then sectioning the first-stage reduced resolution frame into second-stage groups of four pixels per group in a 2×

2 arrangement and generating a second-stage reduced pixel having the averaged properties of the second-stage group of pixels, thereby generating a second-stage reduced resolution frame.

4. The device of claim 2, in which the processor is further enabled such that generating the reduced resolution frame further comprises providing a greater number of color data bits in the averaged pixels than in the pixels from the input frame, such that the reduced resolution frame has less reduction in resolution in color data than in pixel density.

5. The device of claim 4, in which the imaging subsystem is enabled for providing the image data with 16 bit pixels having color data per pixel, and the processor is further enabled such that generating the reduced resolution frame further comprises averaging four adjacent of the 16-bit pixels into one 24-bit pixel having 24 bits of color data per pixel.

6. The device of claim 1, in which the processor is further enabled such that attempting to identify transition pairs comprises measuring differences in at least one of overall brightness and brightness of individual colors between the adjacent pixels in the pairs.

7. The device of claim 1, in which the processor is further enabled such that attempting to identify the transition pairs comprises performing transition search steps from one or more transition search algorithms, including a first algorithm comprising scanning horizontal and/or vertical lines in the reduced resolution frame for transition pairs, and a second algorithm comprising scanning lines going from the edges toward the center of the reduced resolution frame for transition pairs.

8. The device of claim 7, in which the processor is further enabled such that attempting to identify the transition pairs further comprises evaluating potential transition pairs under two or more potential values for the pixel transition threshold.

9. The device of claim 7, in which the processor is further enabled such that attempting to identify the transition pairs further comprises scanning each of the scanned lines for two transition pairs per line.

10. The device of claim 9, in which the processor is further enabled such that attempting to identify the transition pairs further comprises responding to a lack of two transition pairs in a line by re-scanning one or more of the lines with one or more altered values for the pixel transition threshold.

11. The device of claim 1, in which the processor is further enabled such that attempting to identify one or more linear features comprises connecting consecutive identified pixel transitions into identified line segments, identifying sets of line segments that are approximately in-line with each other, and merging identified sets of in-line line segments into identified linear features.

12. The device of claim 1, in which the processor is further enabled for measuring angles between identified linear features, evaluating whether the measured angles are within a constrained skew value around 90 degrees, and if they are, then identifying intersections of the linear features as identified corner points.

13. The device of claim 1, in which the processor is further enabled for evaluating whether four linear features with four corner points can be identified, and if they are not identified, then providing a user aid prompt signal via an output component.

14. The device of claim 1, in which the processor is further enabled for evaluating whether four linear features with four corner points can be identified, and if they are identified, then attempting to calculate a conversion of a two-dimensional quadrilateral defined by the four corners into a rectangular form in three dimensions.

15. The device of claim 14, in which the processor is further enabled for converting an image portion defined by the rectangular form in three dimensions into a corresponding two-dimensional rectangular image portion and saving the two-dimensional rectangular image portion in at least one of the memory components.

16. The device of claim 14, in which the processor is further enabled such that after the rectangular form in three dimensions is calculated, a high-resolution quadrilateral image portion in the input frame corresponding to the quadrilateral defined by the four corners in the reduced resolution frame is converted into a corresponding high-resolution two-dimensional rectangular image portion and saved in at least one of the memory components.

17. The device of claim 14, further comprising an illumination source, and in which the processor is further enabled applying a vignetting compensation to pixels of an image portion representing the rectangular form, wherein the vignetting compensation compensates for vignetting by both an imaging lens of the imaging subsystem and by an offset of the illumination source from the imaging lens.

18. The device of claim 1, in which a series of input frames are continuously provided by the imaging subsystem and buffered by the first memory component while the processor performs processing steps until a rectangle in three dimensions is identified in at least one reduced resolution frame.

19. A method, performed using one or more processors, comprising:

receiving an input frame from a first memory component;

generating, using at least one of the processors, a reduced resolution frame based on the input frame, the reduced resolution frame comprising fewer pixels than the input frame, in which a pixel in the reduced resolution frame combines information from two or more pixels in the input frame;

attempting, using at least one of the processors, to identify transition pairs comprising pairs of adjacent pixels in the reduced resolution frame having differences between the pixels that exceed a pixel transition threshold;

attempting, using at least one of the processors, to identify one or more linear features between two or more identified transition pairs in the reduced resolution frame; and

providing an indication of one or more identified linear features in the reduced resolution frame.

20. A computer-readable storage medium comprising executable instructions capable of configuring one or more processors for:

generating, using at least one of the processors, a reduced resolution frame based on an input frame of image data, the reduced resolution frame comprising fewer pixels than the input frame, in which a pixel in the reduced resolution frame combines information from two or more pixels in the input frame;

attempting, using at least one of the processors, to identify transition pairs comprising pairs of adjacent pixels in the reduced resolution frame having differences between the pixels that exceed a pixel transition threshold;

attempting, using at least one of the processors, to identify one or more linear features between two or more identified transition pairs in the reduced resolution frame; and

providing an indication of one or more identified linear features in the reduced resolution frame.

21. The computer-readable storage medium of claim 20, in which the executable instructions are further capable of configuring one or more processors such that:

generating the reduced resolution frame based on the input frame comprises;

sectioning a 640×

480 input frame into first-stage groups of four pixels per group in a 2×

2 arrangement and generating a first-stage reduced pixel having the averaged properties of the first-stage group of pixels, thereby generating a 320×

240 R5G6B5 first-stage reduced resolution frame;

then sectioning the first-stage reduced resolution frame into second-stage groups of four pixels per group in a 2×

2 arrangement and generating a second-stage reduced pixel having the averaged properties of the second-stage group of pixels, thereby generating a 160×

120 R8B8G8 second-stage reduced resolution frame;

attempting to identify transition pairs comprises;

scanning lines in the 160×

120 R8B8G8 second-stage reduced resolution frame and, for pairs of adjacent pixels in the lines, evaluating whether the pixels in the pair of adjacent pixels exhibit changes in brightness and/or color above a pixel transition threshold, thereby generating identified transition pairs; and

attempting to identify linear features between identified transition pairs comprises;

connecting consecutive identified pixel transitions in the 160×

120 R8B8G8 second-stage reduced resolution frame into identified line segments, attempting to identify sets of line segments that are within constrained error values of being in-line with each other, merging identified sets of in-line line segments into identified linear features, attempting to identify corner points among the identified linear features, attempting to identify a two-dimensional quadrilateral defined by the corner points, attempting to calculate a conversion of a two-dimensional quadrilateral defined by the four corners into a rectangular form in three dimensions, converting an image portion defined by the rectangular form in three dimensions into a corresponding two-dimensional rectangular image portion, and saving the two-dimensional rectangular image portion in at least one memory component.