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By: Rachel Yuen, Chad Van De Hey, and Jake Trotman

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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?


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