Method and apparatus for removing shadow from aerial or satellite photograph

• US 9,299,129 B2
• Filed: 10/29/2013
• Issued: 03/29/2016
• Est. Priority Date: 03/29/2013
• Status: Active Grant

• Current Assignee: Hyundai AutoEver Corp. (Hyundai Mobis Co., Ltd.)
• Original Assignee: Hyundai Mnsoft, Inc. (Hyundai Mobis Co., Ltd.)
• Inventors: Ju, Chanjin
• Primary Examiner(s): YANG, WEI WEN
• Application Number:
  US14/065,886
• Publication Number:
  US 20140294232A1
• Time in Patent Office: 882 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06T 2207/10032 Satellite or aerial image; Remote sensing
• CPC Class Codes: G06T 2207/20221 Image fusion; Image merging
• CPC Class Codes: G06T 2207/30184 Infrastructure
• CPC Class Codes: G06T 5/00 Image enhancement or restoration
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 5/77 Retouching; Inpainting; Scratch removal
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement

Abstract

A method for removing a shadow from an aerial or satellite photograph, includes collecting aerial or satellite photographs, by the photographing information collecting unit; extracting buildings at each of the collected aerial or satellite photographs, by the building information extracting unit; and estimating a shadow area cast by the extracted buildings, by the shadow area estimating unit. Further, the method includes restoring a shaded image in the aerial or satellite photograph, which corresponds to the estimated shadow area, by the image restoration unit; and composing the restored image and a residual image of the aerial or satellite photograph except the shadow area, by the image composition unit.

Claims

1. A method for removing a shadow from an aerial or satellite photograph, the method being performed by a shadow removal apparatus implemented by a processor, which includes a photographing information collecting unit, a building information extracting unit, a shadow area estimating unit, an image restoration unit, and an image composition unit, the method comprising:

collecting through the photographing information collecting unit aerial or satellite photographs taken by and received from a photographing equipment;

extracting buildings at each of the collected aerial or satellite photographs, by the building information extracting unit;

estimating a shadow area cast by the extracted buildings, by the shadow area estimating unit;

restoring a shaded image in the aerial or satellite photograph, which corresponds to the estimated shadow area, by the image restoration unit; and

composing the restored image and a residual image of the aerial or satellite photograph except the shadow area, by the image composition unit,

wherein the photographing information collecting unit is further configured to acquire information including at least one of a photographing location, a flight height and a photographing time for said each of the aerial or satellite photographs, and an angle of view of the photographing equipment when the photographing equipment takes said each of the aerial or satellite photographs, and

wherein the building information extracting unit is further configured to extract the buildings that are taller than or equal to a preset standard height, when it extracts buildings in said each of the collected aerial or satellite photographs, the preset standard height having a different value according to the angle of view of the photographing equipment and the photographing time.

2. The method of claim 1, wherein said estimating the shadow area cast by the extracted buildings comprises:

estimating a shape of the shadow area based on the photographing time of the aerial or satellite photograph and a floor surface shape and height of the extracted buildings; and

extracting a boundary of the shape of the estimated shadow area.

3. The method of claim 2, wherein said estimating a shape of the shadow area comprises estimating an orientation and size of the shadow to be cast.

4. The method of claim 1, wherein said restoring a shaded image in the collected aerial or satellite photograph, which corresponds to the estimated shadow area comprises changing brightness and contrast between light and darkness of the shaded image itself in the aerial or satellite photograph, which corresponds to the estimated shadow area to thereby restore the shaded image in the aerial or satellite photograph.

5. The method of claim 1, wherein said restoring a shaded image in the collected aerial or satellite photograph, which corresponds to the estimated shadow, comprises:

extracting a un-shaded image, which matches the estimated shadow area, from another aerial or satellite photograph that is taken at a different photographing time and substituting the shaded image with the extracted un-shaded image, to thereby restore the shaded image in the aerial or satellite photograph.

6. The method of claim 5, wherein said restoring a shaded image in the aerial or satellite photograph, which corresponds to the shadow area, comprises:

extracting a un-shaded image, which matches a boundary area of the estimated shadow area, from another aerial or satellite photograph that is taken at a different photographing time; and

substituting the shaded image with the extracted un-shaded image, to thereby restore the shaded image in the aerial or satellite photograph.

7. An apparatus for removing a shadow from an aerial or satellite photograph, the apparatus comprising at least a processor implementing:

a photographing information collecting unit configured to collect aerial or satellite photographs taken by and received from a photographing equipment;

a building information extracting unit configured to extract buildings in each of the collected aerial or satellite photographs;

a shadow area estimating unit configured to estimate a shaded area cast by the extracted buildings;

an image restoration unit configured to restore a shaded image in the aerial or satellite photograph, which corresponds to the estimated shadow area; and

an image composition unit configured to compose the restored image and a residual image of the aerial or satellite photograph except the shadow area,

wherein the photographing information collecting unit is further configured to acquire information including at least one of a photographing location, a flight height and a photographing time for said each of the aerial or satellite photographs, and an angle of view of the photographing equipment when the photographing equipment takes said each of the aerial or satellite photographs, and

wherein the building information extracting unit is further configured to extract the buildings that are taller than or equal to a preset standard height having a different value according to the angle of view of the photographing equipment and the photographing time.

8. The apparatus of claim 7, wherein the shadow area estimating unit comprises:

a shape estimator configured to estimate a shape of the shadow area based on the photographing time of the aerial or satellite photograph and a floor surface shape and a height of the extracted buildings; and

a boundary extractor configured to extract a boundary of the shape of the estimated shadow area.

9. The apparatus of claim 8, wherein the shape estimator is configured to estimate an orientation and size of the shadow to be cast.

10. The apparatus of claim 7, wherein the image restoration unit is configured to:

change brightness and contrast between light and darkness of the shaded image itself in the aerial or satellite photograph, which corresponds to the estimated shadow area, thereby restoring the shaded image in the aerial or satellite photograph.

11. The apparatus of claim 7, wherein the image restoration unit is configured to:

extract a un-shaded image, which matches the estimated shadow area, from another aerial or satellite photograph that is taken at a different photographing time and substitute the shaded image with the extracted un-shaded image, thereby restoring the shaded image in the aerial or satellite photograph.

12. The apparatus of claim 11, wherein the image restoration unit is configured to:

extract a un-shaded image, which matches a boundary area of the estimated shadow area, from another aerial or satellite photograph that is taken at a different photographing time; and

substitute the shaded image with the extracted un-shaded image, thereby restoring the shaded image in the aerial or satellite photograph.