Method of locating highly variable brightness or color regions in an image

• US 6,377,698 B1
• Filed: 11/16/1998
• Issued: 04/23/2002
• Est. Priority Date: 11/17/1997
• Status: Expired due to Term

• Current Assignee: Datalogic S.p.A.
• Original Assignee: Datalogic S.p.A.
• Inventors: Cumoli, Marco, Amorosi, Stefano, Saporetti, Claudio
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): Werner, Brian P.
• Application Number:
  US09/192,268
• Time in Patent Office: 1,254 Days
• Field of Search: 382/100, 382/101, 382/112, 382/141, 382/143, 382/151, 382/164, 382/165, 382/173, 382/197, 382/205, 382/282, 382/291, 382/306, 270/52.01, 379/910, 235/462.03, 235/462.11, 235/462.24, 235/462.41, 235/462.08, 235/900, 235/462-1-4, 235/462.17
• US Class Current: 382/101
• CPC Class Codes: G06K 7/1092 sensing by means of TV-scanning
• CPC Class Codes: G06K 7/1093 sensing, after transfer of the image of the data-field to an intermediate store, e.g. storage with cathode ray tube
• CPC Class Codes: G06K 7/1443 locating of the code in an image

Abstract

A method of locating highly variable brightness or color regions in an image having at least one specifically ordered region corresponding, for example, to the image of an optical code defined by different-colored elements with a predetermined orientation and at least one highly variable brightness or color region of an order level other than that of the specifically ordered region. A first intermediate binary image is generated representing the acquired image divided into a number of contiguous first subimages, each having a first logic value if corresponding to a specifically ordered region and a second logic value otherwise. A second intermediate binary image is generated representing the acquired image divided into a number of contiguous second subimages, each having a first logic value if corresponding to a specifically ordered region and/or to a highly variable brightness or color region and a second logic value otherwise. The first intermediate binary image is subtracted from the second intermediate binary image to generate an output binary image defined by a number of contiguous subimages having the first logic value only at the highly variable brightness or color regions.

Claims

1. A method of locating highly variable brightness or color regions in an acquired image (I), wherein said image (I) has a number of relevant regions, each of said regions having an order comprised of one of an identifying geometrical arrangement, a color arrangement and brightness arrangement, said regions including at least one specifically ordered region (Zc);

and at least one highly variable brightness or color region (Za);

the order of said highly variable brightness or color region differing from the order of the specifically ordered region;

said method comprising the steps of;

performing a first processing step of said image (I) to generate a first intermediate binary image (Ir1) based on gradient directions in said acquired image, and representing the acquired image (I) divided into a number of first subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region and a second logic value otherwise;

performing a second processing step of said acquired image (I) to generate a second intermediate binary image (Ir2) based on gradient amplitudes in said acquired image, and representing the image (I) divided into a number of second subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region or a detected highly variable brightness or color region and a second logic value otherwise;

comparing the first intermediate binary image (Ir1) and the second intermediate binary image (Ir2) to generate an output binary image (Iu) defined by a number of subimages (Ip) having a first logic value only at said highly variable brightness or color regions and said second logic value elsewhere.

2. A method as claimed in claim 1, wherein the dimensions of said first subimages correspond with the dimensions of said second subimages.

3. A method as claimed in claim 1, wherein said comparing step comprises a masking step in which the following operation is performed:

4. A method of locating highly variable brightness or color regions according to claim 1, wherein said first subimages are contiguous and said second subimages are contiguous.

5. A method of locating highly variable brightness or color regions in an acquired image (I), wherein said image (I) has a number of relevant regions, each of said regions having an order comprised of one of an identifying geometrical arrangement, a color arrangement and brightness arrangement, said regions including at least one specifically ordered region (Zc), and at least one highly variable brightness or color region (Za), the order of said highly variable brightness or color region differing from the order of the specifically ordered region;

said method comprising the steps of;

performing a first processing step of said image (I) to generate a first intermediate binary image (Ir1) representing the acquired image (I) divided into a number of first subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region and a second logic value otherwise;

performing a second processing step of said acquired image (I) to generate a second intermediate binary image (Ir2) representing the image (I) divided into a number of second subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region or a detected highly variable brightness or color region and a second logic value otherwise;

comparing the first intermediate binary image (Ir1) and the second intermediate binary image (Ir2) to generate an output binary image (Iu) defined by a number of subimages (Ip) having a first logic value only at said highly variable brightness or color region and a second logic value elsewhere, wherein said first processing step of said acquired image (I) comprises the steps of;

calculating a number of gradient vectors for a number of elementary images (If) into which said image (I) is divided;

determining significant gradients of an amplitude above a threshold value;

assigning said first logic value to the first subimages (Ip) containing significant gradient vectors of an order congruent with the order of said specifically ordered region;

assigning said second logic value to the first subimages (Ip) containing significant gradient vectors of an order other than the order of said specifically ordered region; and

assigning said second logic value to the first subimages (Ip) containing nonsignificant gradient vectors;

and said second processing step of said acquired image (I) comprises the steps of;

calculating a number of gradients for a number of elementary images (If) into which said image (I) is divided;

determining significant gradients of an amplitude above a threshold value;

assigning said first logic value to the second subimages (Ip) containing significant gradients; and

assigning said second logic value to the second subimages (Ip) containing nonsignificant gradients.

6. A method of locating highly variable brightness or color regions in an acquired image (I), wherein said image (I) has a number of relevant regions, each of said regions having an order comprised of one of an identifying geometrical arrangement, a color arrangement and brightness arrangement, said regions including at least one specifically ordered region (Zc), and at least one highly variable brightness or color region (Za), the order of said highly variable brightness or color region differing from the order of the specifically ordered region;

said method comprising the steps of;

performing a first processing step of said image (I) to generate a first intermediate binary image (Ir1) representing the acquired image (I) divided into a number of first subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region and a second logic value otherwise;

performing a second processing step of said acquired image (I) to generate a second intermediate binary image (Ir2) representing the image (I) divided into a number of second subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region or a detected highly variable brightness or color region and a second logic value otherwise;

comparing the first intermediate binary image (Ir1) and the second intermediate binary image (Ir2) to generate an output binary image (Iu) defined by a number of subimages (Ip) having a first logic value only at said highly variable brightness or color region and a second logic value elsewhere, wherein said first processing step of said acquired image (I) comprises;

a first step in which the acquired image (I) is divided into a number of elementary images (If), each comprising a predetermined number (N) of pixels;

each pixel being assigned a value (A, B, C, D) representing the brightness of the pixel;

a second step in which a brightness gradient vector (G) is calculated for each of said elementary images (If);

a first comparing step to select, from the calculated said gradient vectors (G), gradient vectors having an amplitude above at least one threshold value (Glim1) and representing rapid variations in brightness;

a transformation step in which the selected gradient vectors are transformed to determine a given direction and a given side;

which direction and side are assigned to all the gradient vectors;

a tiling step in which said acquired image (I) is divided into a number of said subimages (Ip), each comprising a number of elementary images (If);

a composition step in which the transformed gradient vectors relating to a selected subimage (Ip) are added to calculate a sum gradient vector (Gs);

a second comparing step in which said sum gradient vector (Gs) of each of said subimages (Ip) is compared with reference values to select) significant subimages containing a sufficient number of gradient vectors having substantially the same direction;

the significant subimages being assigned said first logic value (“

1”

);

said second comparing step also determining nonsignificant subimages containing a limited number of gradient vectors having substantially the same direction and the nonsignificant subimages being assigned said second logic value (“

0”

);

said first processing step generating said first intermediate binary image (Ir1) representing said acquired image (I) divided into said subimages (Ip), each having a respective logic value.

7. A method as claimed in claim 6, wherein during said transformation step, the angle (α

) formed by said gradient vector with a cartesian reference system is multiplied by a factor equal to the number of sides of the geometrical figure defining the unit element of an optical code detectable in said specifically ordered region.

8. A method of locating highly variable brightness or color regions in an acquired image (I), wherein said image (I) has a number of relevant regions, each of said regions having an order comprised of one of an identifying geometrical arrangement, a color arrangement and brightness arrangement, said regions including at least one specifically ordered region (Zc), and at least one highly variable brightness or color region (Za), the order of said highly variable brightness or color region differing from the order of the specifically ordered region;

said method comprising the steps of;

performing a first processing step of said image (I) to generate a first intermediate binary image (Ir1) representing the acquired image (I) divided into a number of first subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region and a second logic value otherwise;

performing a second processing step of said acquired image (I) to generate a second intermediate binary image (Ir2) representing the image (I) divided into a number of second subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region or a detected highly variable brightness or color region and a second logic value otherwise;

comparing the first intermediate binary image (Ir1) and the second intermediate binary image (Ir2) to generate an output binary image (Iu) defined by a number of subimages (Ip) having a first logic value only at said highly variable brightness or color region and a second logic value elsewhere, wherein said second processing step of said image (I) comprises;

a third step in which the acquired image (I) is divided into a number of elementary images (If), each comprising a predetermined number (N) of pixels;

each pixel being assigned a value (A, B, C, D) representing the brightness of the pixel;

a fourth step in which a brightness gradient (G) is calculated for each of said elementary images (If);

a third comparing step to select, from the calculated said gradients (G), gradients having an amplitude above at least one threshold value (Glim2) and representing rapid variations in brightness;

a further tiling step in which said acquired image (I) is divided into a number of said subimages (Ip), each comprising a number of elementary images (If);

a further composition step in which the scalar sum of the selected gradient vectors relating to a selected subimage (Ip) is calculated to calculate a sum gradient (Gs);

a fourth comparing step in which said sum gradient (Gs) of each of said subimages (Ip) is compared with reference values to select significant subimages containing a sufficient number of gradients;

the significant subimages being assigned said first logic value (“

1”

);

said fourth comparing step also determining nonsignificant subimages containing a limited number of gradients; and

the nonsignificant subimages being assigned said second logic value (“

0”

);

said second processing step generating said second intermediate binary image (Ir2) representing said acquired image (I) divided into said subimages (Ip), each having a respective logic value.

9. A method of locating highly variable brightness or color regions in an acquired image (I), wherein said image (I) has a number of relevant regions, each of said regions having an order comprised of one of an identifying geometrical arrangement, a color arrangement and brightness arrangement, said regions including at least one specifically ordered region (Zc);

and at least one highly variable brightness or color region (Za);

the order of said highly variable brightness or color region differing from the order of the specifically ordered region;

said method comprising the steps of;

performing a first processing step on gradients of said image (I) to generate a first intermediate binary image (Ir1) representing the acquired image (I) divided into a number of first subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region and a second logic value otherwise;

performing a second processing step on gradients of said acquired image (I) to generate a second intermediate binary image (Ir2) representing the image (I) divided into a number of second subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region or a detected highly variable brightness or color region and a second logic value otherwise;

comparing the fist intermediate binary image (Ir1) and the second intermediate binary image (Ir2) to generate an output binary image (Iu) defined by a number of subimages (Ip) having a first logic value only at said highly variable brightness or color regions and said second logic value elsewhere, wherein said first processing step of said acquired image (I) comprises the steps of;

calculating a number of gradient vectors for a number of elementary images (If) into which said image (I) is divided;

determining significant gradients of an amplitude above a threshold value;

assigning said first logic value to the first subimages (Ip) containing significant gradient vectors of an order congruent with the order of said specifically ordered region;

assigning said second logic value to the first subimages (Ip) containing significant gradient vectors of an order other than the order of said specifically ordered region; and

assigning said second logic value to the first subimages (Ip) containing nonsignificant gradient vectors;

and said second processing step of said acquired image (I) comprises the steps of;

calculating a number of gradients for a number of elementary images (If) into which said image (I) is divided;

determining significant gradients of an amplitude above a threshold value;

assigning said first logic value to the second subimages (Ip) containing significant gradients; and

assigning said second logic value to the second subimages (Ip) containing nonsignificant gradients.

10. A method of locating highly variable brightness or color regions in an acquired image (I), wherein said image (I) has a number of relevant regions, each of said regions having an order comprised of one of an identifying geometrical arrangement, a color arrangement and brightness arrangement, said regions including at least one specifically ordered region (Zc);

and at least one highly variable brightness or color region (Za);

the order of said highly variable brightness or color region differing from the order of the specifically ordered region;

said method comprising the steps of;

performing a first processing step on gradients of said image (I) to generate a first intermediate binary image (Ir1) representing the acquired image (I) divided into a number of fist subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region and a second logic value otherwise;

performing a second processing step on gradients of said acquired image (I) to generate a second intermediate binary image (Ir2) representing the image (I) divided into a number of second subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region or a detected highly variable brightness or color region and a second logic value otherwise;

comparing the first intermediate binary image (Ir1) and the second intermediate binary image (Ir2) to generate an output binary image (Iu) defined by a number of subimages (Ip) having a first logic value only at said highly variable brightness or color regions and said second logic value elsewhere, wherein said first processing step of said acquired image (I) comprises;

a first step in which the acquired image (I) is divided into a number of elementary images (If), each comprising a predetermined number (N) of pixels;

each pixel being assigned a value (A, B, C, D) representing the brightness of the pixel;

a second step in which a brightness gradient vector (G) is calculated for each of said elementary images (If);

a first comparing step to select, from the calculated said gradient vectors (G), gradient vectors having an amplitude above at least one threshold value (Glim1) and representing rapid variations in brightness;

a transformation step in which the selected gradient vectors are transformed to determine a given direction and a given side;

which direction and side are assigned to all the gradient vectors;

a tiling step in which said acquired image (I) is divided into a number of said subimages (Ip), each comprising a number of elementary images (If);

a composition step in which the transformed gradient vectors relating to a selected subimage (Ip) are added to calculate a sum gradient vector (Gs);

a second comparing step in which said sum gradient vector (Gs) of each of said subimages (Ip) is compared with reference values to select) significant subimages containing a sufficient number of gradient vectors having substantially the same direction;

the significant subimages being assigned said first logic value (“

1”

);

said second comparing step also determining nonsignificant subimages containing a limited number of gradient vectors having substantially the same direction and the nonsignificant subimages being assigned said second logic value (“

0”

);

said first processing stop generating said first intermediate binary image (Ir1) representing said acquired image (I) divided into said subimages (Ip), each having a respective logic value.

11. A method as claimed in claim 10, wherein during said transformation step, the angle (α

) formed by said gradient vector with a cartesian reference system is multiplied by a factor equal to the number of sides of the geometrical figure defining the unit element of an optical code detectable in said specifically ordered region.

12. A method of locating highly variable brightness or color regions in an acquired image (I), wherein said image (I) has a number of relevant regions, each of said regions having an order comprised of one of an identifying geometrical arrangement, a color arrangement and brightness arrangement, said regions including at least one specifically ordered region (Zc);

and at least one highly variable brightness or color region (Za);

the order of said highly variable brightness or color region differing from the order of the specifically ordered region;

said method comprising the steps of;

performing a first processing step on gradients of said image (I) to generate a first intermediate binary image (Ir1) representing the acquired image (I) divided into a number of first subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region and a second logic value otherwise;

performing a second processing step on gradients of said acquired image (I) to generate a second intermediate binary image (Ir2) representing the image (I) divided into a number of second subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region or a detected highly variable brightness or color region and a second logic value otherwise;

comparing the first intermediate binary image (Ir1) and the second intermediate binary image (Ir2) to generate an output binary image (Iu) defined by a number of subimages (Ip) having a first logic value only at said highly variable brightness or color regions and said second logic value elsewhere, wherein said second processing step of said image (I) comprises;

a third step in which the acquired image (I) is divided into a number of elementary images (If), each comprising a predetermined number (N) of pixels;

each pixel being assigned a value (A, B, C, D) representing the brightness of the pixel;

a fourth step in which a brightness gradient (G) is calculated for each of said elementary images (If);

a third comparing step to select, from the calculated said gradients (G), gradients having an amplitude above at least one threshold value (Glim2) and representing rapid variations in brightness;

a further tiling step in which said acquired image (I) is divided into a number of said subimages (Ip), each comprising a number of elementary images (If);

a further composition step in which the scalar sum of the selected gradient vectors relating to a selected subimage (Ip) is calculated to calculate a sum gradient (Gs);

a fourth comparing step in which said sum gradient (Gs) of each of said subimages (Ip) is compared with reference values to select significant subimages containing a sufficient number of gradients;

the significant subimages being assigned said first logic value (“

1”

);

said fourth comparing step also determining nonsignificant subimages containing a limited number of gradients; and

the nonsignificant subimages being assigned said second logic value (“

0”

);

said second processing step generating said second intermediate binary image (Ir2) representing said acquired image (I) divided into said subimages (Ip), each having a respective logic value.

13. A method of locating highly variable brightness or color regions in an acquired image (I), wherein said image (I) has a number of relevant regions, each of said regions having an order comprised of one of an identifying geometrical arrangement, a color arrangement and brightness arrangement, wherein said regions including at least one specifically ordered region (Zc) and at least one highly variable brightness or color region (Za) and wherein the order of said highly variable brightness or color region differs from the order of the specifically ordered region;

said method comprising the steps of;

generating a first intermediate binary image (Ir1) based on gradient vectors in said acquired image, and representing the acquired image (I) divided into a number of first subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region and a second logic value otherwise;

generating a second intermediate binary image (Ir2) based on gradient amplitudes in said acquired image, and representing the image (I) divided into a number of second subimages (Ip), each having a first logic value if corresponding to a detected specifically ordered region or a detected highly variable brightness or color region and a second logic value otherwise;

comparing the first intermediate binary image (Ir1) with the second intermediate binary image (Ir2) to generate an output binary image (Iu) defined by a number of subimages (Ip) having a first logic value only at said highly variable brightness or color regions and said second logic value elsewhere.