Image Pyramids
Post on 22-Feb-2016
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Image Pyramids
Computer Vision, winter 2012-13CS Department, Technion
TopicsThe Gaussian PyramidThe Laplacian PyramidApplications:
Pattern MatchingCoding (Compression)EnhancementBlending
Gaussian Pyramid
Gaussian PyramidApproximation filter is not Gaussian
A 5 tap binomial kernel:
2D extension:
1 [1,4,6,4,1]16
1 4 6 4 14 16 24 16 4
16 24 36 24 6
2564 16 24 16 41 4 6 4 1
Pattern Matching
Laplacian Pyramid
Laplacian PyramidApproximation of the Laplacian of each scaleConstructed by Difference of Gaussian (DoG)
layers
Laplacian Pyramid
Image Coding
Enhancement
Enhancement
Pyramid Blending
Step I - Create Blend Masks
Step II
• Weighted sum over each Laplacian pyramid scale (of the images) independently
• Gaussian pyramid of masks, or simple resizing of masks to correct dimensions
Blend 1Blend 1 MaskBlend 2Blend 2 Mask
Step IIIStandard Laplacian pyramid
reconstruction of blended scales
Implementation IssuesImage registrationFeatheringOver/under flows outside [0,1]MATLAB function: impyramid()
Only Gaussian pyramid‘reduce’ or ‘expand’ modes
MATLAB function: imresize()Useful for masks resizing
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