Enhanced data capture from imaged documents
View Patent ↗Methods and apparatus are disclosed for locating an area of interest within a digital image of a form captured by an imaging scanner. Specific examples include methods and apparatus for optical mark reading with a digital imaging scanner. In many of the methods, an image of a response form is captured by a scanner, and target areas for possible responses are located within the image based upon an expected location being adjusted as necessary for certain error-inducing defects in the forms or scanning process. Also disclosed are steps to normalize the darkness values of pixels captured from an optically scanned form.
1. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:
a) locating edges of the captured image of the form within a total pixel scan captured by the scanner;
b) determining a sheet position parameter related to the location of the edges;
c) defining an expected location of the area of interest; and
d) adjusting the expected location based upon the sheet position parameter.
2. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:
a) defining expected locations of preprinted key marks in the image;
b) interrogating pixels within a proscribed area around key mark expected locations to locate key marks in the image;
c) determining a key mark parameter related to the location of the key marks;
d) defining an expected location of the area of interest; and
e) adjusting the expected location of the area of interest based upon the key mark parameter.
3. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:
a) locating edges of the captured image of the form within a total pixel scan captured by the scanner;
b) determining a sheet position parameter related to the location of the edges;
c) defining expected locations of preprinted key marks in the image;
d) adjusting the key mark expected locations based upon the sheet position parameter;
e) interrogating the pixels within a proscribed area around each adjusted key mark expected location to locate the key marks in the image;
f) determining key mark parameters related to the location of the key marks;
g) defining an expected location of the area of interest; and
h) adjusting the expected location of the area of interest based upon a key mark parameter.
4. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:
a) defining expected locations of preprinted speed marks in the image;
b) interrogating the pixels within a proscribed area around expected speed mark locations to locate the speed marks in the image;
c) determining a scanning speed parameter related to spacings between the speed marks;
d) defining an expected location of the area of interest; and
e) adjusting the expected location of the area of interest based upon the scanning speed parameter.
5. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:
a) locating edges of the captured image of the form within a total pixel scan captured by the scanner;
b) determining a sheet position parameter related to the location of the edges;
c) defining expected locations of preprinted speed marks in the image;
d) adjusting the speed mark expected locations based upon the sheet position parameter;
e) interrogating pixels within a proscribed area around adjusted speed mark expected locations to locate the speed marks in the image;
f) determining a scanning speed parameter related to spacings between the speed marks;
g) defining an expected location of the area of interest; and
h) adjusting the expected location of the area of interest based upon the scanning speed parameter.
6. The method of claim 5 , comprising the additional step of adjusting the expected location of the area of interest based upon the sheet position parameter.
7. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:
a) locating edges of the captured image of the form within a total pixel scan captured by the scanner;
b) determining a sheet position parameter related to the location of the edges;
c) defining expected locations of preprinted speed marks in the image;
d) adjusting the speed mark expected locations based upon the sheet position parameter;
e) interrogating pixels within a proscribed area around adjusted speed mark expected locations to locate the speed marks in the image;
f) determining a scanning speed parameter related to spacings between the speed marks;
g) defining expected locations of preprinted key marks in the image;
h) adjusting the key mark expected locations based upon the scanning speed parameter;
i) interrogating pixels within a proscribed area around each adjusted key mark expected location to locate the key marks in the image;
j) determining a key mark parameter related to the location of the key marks;
k) defining an expected location of the area of interest; and
l) adjusting the expected location of the area of interest based upon a key mark parameter.
8. The method of claim 7 comprising the additional step of adjusting the expected location of the area of interest based upon the scanning speed parameter.
9. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:
a) defining an expected location for the area of interest based upon an idealized captured image of the form;
b) locating the digital image of the form within a total pixel scan captured by the scanner;
c) calculating a sheet position parameter related to the location of the digital image of the form; and
d) adjusting the expected location for the area of interest based upon the sheet position parameter.
10. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:
a) defining an expected location for the area of interest based upon an idealized captured image of the form;
b) defining an expected location of preprinted key marks based upon an idealized captured image of the form;
c) interrogating pixels within a proscribed area around the expected locations of a plurality of key marks to locate those key marks in the captured image of the form;
d) determining a key mark parameter related to the location of the key marks in the captured image; and
e) adjusting the expected location of the area of interest based upon the key mark parameter.
11. A method of locating an area of interest within a digital image of a form captured by an imaging scanner, said method comprising the steps of:
a) defining an expected location for the area of interest based upon an idealized captured image of the form;
b) defining an expected location of preprinted speed marks based upon an idealized captured image of the form;
c) interrogating pixels within a proscribed area around the expected locations of the speed marks to locate those speed marks in the captured image;
d) determining a scanning speed parameter related to the spacing of the speed marks in the captured image; and
e) adjusting the expected location of the area of interest based upon the scanning speed parameter.
12. A method of optical mark reading (OMR) with a digital imaging scanner, said method comprising the steps of:
a) scanning with a digital imaging scanner a sheet with a plurality of OMR response targets to capture an image of the sheet and any OMR response marks made thereon;
b) locating edges of the captured image of the sheet within a total pixel scan captured by the scanner;
c) determining a sheet position parameter related to the location of the edges;
d) defining an expected location of an OMR response target based upon an idealized captured image of the sheet;
e) adjusting the expected location of the OMR response target based upon the sheet position parameter;
f) interrogating the darkness value of a plurality of pixels within a proscribed area determined from the adjusted expected location of the OMR response target; and
g) making a goodness of mark determination based upon the darkness values.
13. A method of optical mark reading (OMR) with a digital imaging scanner, said method comprising the steps of:
a) scanning with a digital imaging scanner a sheet with a plurality of OMR response targets and preprinted key marks to capture an image of the sheet and any OMR response marks made thereon;
b) locating key marks in the captured image of the sheet;
c) determining a key mark parameter based upon the location of the key marks in the captured image;
d) defining an expected location of an OMR response target based upon an idealized captured image of the sheet;
e) adjusting the expected location of the OMR response target based upon the key mark parameter;
f) interrogating the darkness value of a plurality of pixels within a proscribed area determined from the adjusted expected location of the OMR response target; and
g) making a goodness of mark determination based upon the darkness values.
14. A method of optical mark reading (OMR) with a digital imaging scanner, said method comprising the steps of:
a) scanning with a digital imaging scanner a sheet with a plurality of OMR response targets and speed marks to capture an image of the sheet and any OMR response marks made thereon;
b) locating speed marks in the captured image of the sheet;
c) determining a scanning speed parameter based upon the location of the speed marks in the captured image;
d) defining an expected location of an OMR response target based upon an idealized captured image of the sheet;
e) adjusting the expected location of the OMR response target based upon the scanning speed parameter;
f) interrogating the darkness value of a plurality of pixels within a proscribed area determined from the adjusted expected location of the OMR response target; and
g) making a goodness of mark determination based upon the darkness values.