METHOD OF REALISM ASSESSMENT OF AN IMAGE COMPOSITE

• US 20110141353A1
• Filed: 12/14/2009
• Published: 06/16/2011
• Est. Priority Date: 12/14/2009
• Status: Active Grant

• Current Assignee: National Taiwan University (Government of The Republic of China)
• Original Assignee: National Taiwan University (Government of The Republic of China)
• Inventors: WONG, BING-YI, LIANG, CHIA-KAI, CHEN, Homer H., LIN, TAI-HSU
• Granted Patent: US 8,373,721 B2
• Time in Patent Office: Days
• US Class Current: 348/453
• CPC Class Codes: G06T 11/001 Texturing; Colouring; Generation of texture or colour inpainting G06T5/77

Abstract

In a method of realism assessment of an image composite, the foreground and the background are transformed into a color space, such as YCbCr, followed by projecting the foreground and the background to a subspace represented by the axes representing chromatic information. The image composite is assessed in the projected subspace, according to linearity of color distributions of the foreground/the background, or according to distance between the color distributions of the foreground/the background and a center of the transformed color space.

Claims

1. A method of realism assessment of an image composite, comprising:

providing the image composite having a foreground and a background;

transforming the foreground and the background into a color space, wherein the transformed color space has a first axis representing luminance information, and a second axis and a third axis representing chromatic information;

projecting the foreground and the background to a subspace represented by the second axis and the third axis; and

assessing the image composite, in the projected subspace, according to a linearity of color distribution of the foreground and a linearity of color distribution of the background, and further according to a relationship between the color distribution of the foreground and the color distribution of the background.

2. The method of claim 1, wherein the foreground is an inserted object of the image composite.

3. The method of claim 1, wherein the transformed color space is YCbCr color space, and the first axis is Y axis, the second axis is Cb axis, and the third axis is Cr axis.

4. The method of claim 1, wherein the transformed color space is YUV color space or L*a*b* color space.

5. The method of claim 1, wherein the image composite is assessed as realistic when the foreground and the background have linear color distributions that are approximately consistent or when neither the foreground nor the background has a linear color distribution, and wherein the image composite is assessed as unrealistic when the foreground and the background have linear color distributions that are substantially inconsistent.

6. The method of claim 1, further comprising a step of:

firstly rotating color distribution of the foreground and/or the background around the first axis, such that the color distribution of the foreground is approximately aligned or parallel with the color distribution of the background in the projected subspace.

7. The method of claim 6, further comprising a step of:

secondly rotating the color distribution of the foreground and/or the background around the second axis or the third axis, such that the color distribution of the foreground is approximately aligned or parallel with the color distribution of the background in a subspace represented by the first axis and the third axis or in a subspace represented by the first axis and the second axis.

8. A method of realism assessment of an image composite, comprising:

providing the image composite having a foreground and a background;

transforming the foreground and the background into a color space, wherein the transformed color space has a first axis representing luminance information, and a second axis and a third axis representing chromatic information;

measuring distances between color distributions of the foreground and the background respectively and a center of the transformed color space as grayness; and

assessing the image composite, in the transformed subspace, according to the measured grayness of the foreground and the grayness of the background.

9. The method of claim 8, wherein the foreground is an inserted object of the image composite.

10. The method of claim 8, wherein the transformed color space is YCbCr color space, and the first axis is Y axis, the second axis is Cb axis, and the third axis is Cr axis.

11. The method of claim 8, wherein the transformed color space is YUV color space or L*a*b* color space.

12. The method of claim 8, wherein the grayness is measured as negative of a distance from the center of the transformed color space to a nearest point of the color distribution of the foreground or the background.

13. The method of claim 8, wherein the image composite is assessed as unrealistic when a hollow region exists between the color distribution of the foreground and the color distribution of the background, and otherwise the image composite is assessed as realistic.

14. The method of claim 8, further comprising a step of:

firstly rotating color distribution of the foreground and/or the background around the first axis, such that the color distribution of the foreground is approximately aligned or parallel with the color distribution of the background in the projected subspace.

15. The method of claim 14, further comprising a step of:

secondly rotating the color distribution of the foreground and/or the background around the second axis or the third axis, such that the color distribution of the foreground is approximately aligned or parallel with the color distribution of the background in a subspace represented by the first axis and the third axis or in a subspace represented by the first axis and the second axis.

16. A method of realism assessment of an image composite, comprising:

providing the image composite having a foreground and a background;

shrinking the foreground and the background to obtain local color distributions of the foreground and the background; and

determining color similarity between the shrunk foreground and the shrunk background by histogram distance.

17. The method of claim 16, wherein the foreground is an inserted object of the image composite.

18. The method of claim 17, wherein the shrunk background is a band region outside a boundary of the inserted object, and the shrunk foreground is a band region inside the boundary of the inserted object.

19. The method of claim 16, wherein the determined color similarity S is expressed as

20. The method of claim 16, further comprising a step of:

adjusting histogram of the shrunk foreground and the shrunk background such that distribution of the shrunk foreground and distribution of the shrunk background are approximately matched.

21. The method of claim 20, wherein the histogram adjustment is performed by:

transforming, channel-by-channel, color of each pixel of the shrunk foreground in CIE L*a*b* space by using the following equation,

c′

=(σ

_B/σ

_F)(c−

μ

_F)+μ

_B,

where c denotes a value of the pixel in an input image for a given channel, c′

denotes a modified pixel value, μ

denotes mean, a denotes standard deviation, subscript B stands for the shrunk background, and subscript F stands for the shrunk foreground.