PDF COL783: Digital Image Processing

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COL783: Digital Image Processing

Prem Kalra

[email protected]

http://www.cse.iitd.ac.in/~pkalra/col783

Department of Computer Science and Engineering

Indian Institute of Technology Delhi

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Recap: Image Enhancement in Spatial Domain

Laplace Filter

Image Subtraction

Image Addition

Convolution

Half Toning

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Digital Image Processing http://www.cse.iitd.ac.in/~pkalra/col783

Image Enhancement in Spatial Domain

Convolution

1D Continuous Domain

1D Discrete Domain

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Image Enhancement in Spatial Domain

Convolution: Properties Commutativity

F*H=H*F Associativity

(F*H 1 )*H 2 =F*(H 1 *H 2 ) Linearity

(s.F)*H=s.(F*H)

(F 1 +F 2 )*H=(F 1 *H)+(F 2 *H)

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Image Enhancement in Spatial Domain

Convolution: Properties Separability H=H

1

* H

₂

* H

₃

* H

₄

….. * H

_m

F*H=F * (H

₁

* H

₂

* H

₃

* H

₄

….. * H

_m

)

F*H=(…((F *H

₁

)* H

₂

) *….. * H

_m

)

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Halftoning

Thresholding

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Halftoning

Thresholding

plus random noise

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Halftoning

Area based approach

Pseudo grey levels (quantization)

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Halftoning

Floyed Steinberg Method

Error Diffusion

• Quantizes each pixel using a neighborhood operation, rather than a simple point wise operation.

• Moves through image in raster order, quantizing the result, and “pushing” the error forward.

• Can produce better quality images

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Halftoning

Error Diffusion

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Halftoning

Error Diffusion

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Halftoning

Error Diffusion

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Halftoning

Error Diffusion

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Halftoning

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Color Image Quantization

Halftoning

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Color Image Quantization

Halftoning

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Transfer color to grey level images

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Image Stylization

Assignment 1