A New Texture Descriptor: Composite Sub_band

Gradient Vector

2006.3.30

Texture Analysis by Gradient-Based Feature Gradient operator (Sobel) reflect the magnitud

e and direction.

Summing up the magnitude in the same direction.

Every successive k(=10) directions grouped together

)(tan),( 1

Gx

Gyyx

GyGxf

Euclidean distance: measure the difference between two gradient vector.

d

ii babadist1

2)(),(

Composite Subband Gradient Vector drawback

LL sub-image: Both horizontal and vertical direction have low-frequencies.

LH sub-image: Horizontal direction has low-frequencies and vertical direction has high-frequencies

HL sub-image: Horizontal direction has high-frequencies and vertical direction has low-frequencies.

HH sub-image: Both horizontal and vertical direction have high-frequencies.

SGV1 be the sub-image LL SGV2 be the sub-image LH SGV3 be the sub-image HL SGV4 be the sub-image HH

CSGV = SGV1|| SGV2|| SGV3|| SGV4(where || is append operator)

CSGV is called Composite Subband Gradient Vector

(g)=>(h)

(g)=>(i)

Dist.

5.5099 16.6057

Segmentation using Reduced-Length CSG Vectors

Segmentation process into three stages:(1).split stage.(2).merge stage.(3).boundary stage.

Assume that an image I is of size m*m pixels

Split stage.

Merge stage.

Boundary stage.

Result(Split:0.1 Merge:0.7)