enhancement of color in digital images

1. Color Image Enhancement with
a Human Visual System Based
Adaptive Filter
Presented by
K. ANURAMA
12S11D6502

2. Abstract
 Proposed method
 New color image enhancement algorithm
- Based on human visual system adaptive filter
• Dividing three major parts
– Adaptive adjustment
– Color restoration
– Unlike traditional color image enhancement algorithms
• Use of color space conversion
– Much better visibility
• Better effectiveness in reducing halo and color
distortion

3. Introduction
Image enhancement technology
– Problem of many factors
• Limited dynamic range
• Lighting influences
• Display device
– Not suitable to directly use gray image
enhancement technologies for color images

4. Color image enhancement technologies
Based on human visual characteristics
 Retinex
– Very good enhanced result
– Color distortion
– Complex of calculation
 Li Tao and VijayanK. Asari
– Robust color image enhancement algorithm
 Use of Gaussian filter
 Inaccurate estimation

5. Color image enhancement technologies
– New bio-inspired color image enhancement algorithm
Combination of retinex and Li Tao and VijayanK. Asari algorithm
Use of bilateral filter
• New algorithm
– Consideration of color information
– Use of adaptive filter to get the background image

6. HALO EFFECT
 Halo artifacts are due to the
proximity of two areas of very
different intensity.
 For example, if a dim area is
close to a bright window, the
bright pixels can influence the
processing of the dim area and
can cause a black halo around the
bright area. Moreover, local
filtering tends to make pure black
and pure white low contrast areas
turn gray. These phenomena are
illustrated in Fig. 1. The shadow
on the face is a halo artifact due
to the background window. The
black t-shirt looks washed out
due to the local filtering
Fig. 1. Example of halo artifacts and graying-out.
The shadow on the face is a halo artifact due to
the background window. The black t-shirt looks
washed out due to the local filtering

7. Color Image Enhancement algorithm
 Proposed method
– Framework of color enhancement algorithm
Fig. 1. The Framework of the proposed color image enhancement algorithm.

10. •
Fig. 2. The Example of luminance image and background image: from up to down, the
original image, luminance image and background image

12. Image enhancement process
Using proposed algorithm
Fig. 3. Enhanced results of using the proposed algorithm. The left are original, and
the right are enhanced images

13. Comparison with other techniques
Compared to the
traditional algorithms
Fig. 4. Illustrate the difference of using different algorithm: (a) the algorithm in [4];
(b) the algorithm in [5]; (c) Retinex; (d) proposed algorithm 11

14. Fig. 11. Top: Gamma-encoded image.
Middle: Image treated with the
adaptive
filter method. Bottom: Image treated
with the fast bilateral filtering method.

15. Conclusion
Proposed method
– New color image enhancement algorithms
• Considering human visual properties
• Improvement of visual qualities of enhanced images
– Adaptive filter considering color information
– Utilizing color space conversion to get luminance
image