1. By: Rachel Yuen, Chad Van De Hey, and Jake Trotman
Single Image Haze Removal Using Dark Channel Prior and Other Techniques
By: Rachel Yuen, Chad Van De Hey, and Jake Trotman

2. Problem Statement
Accurately determine which areas are hazy and which are not
Complete all rendering in a reasonable amount of time (30 seconds to a minute, if possible)

3. Motivation
Dark Channel Prior: Scene restoration and depth estimation

4. Method Breakdown Compute Dark Channel Prior Estimate Atmospheric Light
Local intensity patches over the image
Sky region has high intensity
Statistical observation of outdoor pictures in nature
Estimate Atmospheric Light
Select top 0.1%-0.2% brightest pixels in the dark channel
Reduces error for white objects
Input
Jdark

5. Method Breakdown Estimate Transmission Recover Scene Radiance
Minimal operation on a channel basis
Gives better result for sky region
Transmission
Recover Scene Radiance
Use transmission map and haze removal equation
Recovered

6. Method Breakdown Apply Matting Recover Scene Radiance
Transmission
Apply Matting
Currently using soft matting
Creates a refined and accurate transmission map
Recover Scene Radiance
New transmission map
Input
Output

7. Results Thus Far

8. Performance Improvement Methods
Guided Filter
Fast Matting
A.I.

9. Guided Filtering
Retrieve the transmission variable “T” from a “down sampled” image and “up sample” with a guided filter.
Guided filter function in Matlab.
Image dehazing time performance becomes linear to its size.

10. Fast Matting Gaussian filter to smooth image after removing artifacts.
Use large kernel matting laplacian matrices instead of soft matting.

11. A.I. Methods
Bays Nets and K-Nearest Neighbors methods to accurately estimate the atmospheric variable “A” using a probability function over density of the haze.

12. Advantages/Disadvantages
Soft Matting: slow ~15 min computation time for 800x600 image
Artifacts seen in sky region
Fast Matting: Improves speed of soft matting by ~15 times with an 800x800 image.
Guided Filtering: Lowers the complexity of the computationally heavy part of the algorithm.
Guided Filter: Reduces artifacts produced in sky region

13. Questions?