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# Chapter 8 Computer Vision - PowerPoint PPT Presentation

Chapter 8 Computer Vision. Contents. What is Image Processing? Digital Image Processing Electromagnetic Spectrum Steps in Digital Image Processing. What is Image Processing?. Application Area. Image Processing Fields. Image Processing Fields. Digital Image Processing.

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Presentation Transcript

### Chapter 8 Computer Vision

• What is Image Processing?

• Digital Image Processing

• Electromagnetic Spectrum

• Steps in Digital Image Processing

Chapter 9

Chapter 9

Chapter 9

Chapter 9

Chapter 9

• “Digital Image”?

• Digital

• Image

• “Image Processing”?

Chapter 9

What is a signal?

A signal is a function that maps a set (domain) to another set (range)

Chapter 9

A signal is a function that maps a set (domain) to another set (range)

For each point in time (t), assign a voltage value (y(t)).

Domain = time interval

Range = voltage interval

Chapter 9

• Image

• An image is a two-dimensional signal

A signal is called two-dimensional

if the domain is two-dimensional

Chapter 9

• Image

• An image is a two-dimensional signal

Chapter 9

• Digital Image

• Vs Analog image?

• Digital vs analog signal

Chapter 9

• Domain

• Range

• Countable

• Quantized Signal

Chapter 9

• A signal is “digital”

• if both the domain andthe rangeare countable

• I.e., if it is a quantized discrete-time (or -space) signal

Chapter 9

• Digital Image

• A digital image is a two-dimensional signal with a countable domain and a countable range

Chapter 9

• Digital Image

Chapter 9

• How is a digital signal formed?

• Discrete domain

• Domain is inherently discrete, or

• Sample a continuous interval

• Discrete range

• Range is inherently discrete, or

• Sample a continuous interval

Chapter 9

• Continuous-time signals

• t and y (t) have physical meanings

• Digital signals

• n and y (n) do not have physical meanings and can be arbitrary

Chapter 9

Chapter 9

1921

Range has 5 values!

1922

1929

Chapter 9

1 2 3 4 5 6 7

Electromagnetic Spectrum : EM

Chapter 9

1. Gamma-Ray Imaging 6 7

Chapter 9

2. X-ray Imaging 6 7

Chapter 9

3. UV Imaging 6 7

Chapter 9

4. Visible Range 6 7

Chapter 9

4. Visible Range 6 7

1964

Chapter 9

4. Visible Range 6 7

Chapter 9

4. Multispectral: 6 7 Visible+Infrared Bands

Chapter 9

5. Infrared Range 6 7

Chapter 9

7. Radio Band Imaging 6 7

Chapter 9

Ultrasound Image 6 7

Chapter 9

4 6 7

5

6

7

8

3

11

2

9

1

10

Steps in Digital Image Processing

Chapter 9

1 6 7

Chapter 9

2 6 7

Chapter 9

Distorted image 6 7

Restore image

3

Chapter 9

4 6 7

Chapter 9

5 6 7

Chapter 9

6 6 7

Chapter 9

7 6 7

Chapter 9

8 6 7

Chapter 9

9 6 7

Chapter 9

9 6 7

Chapter 9

10 6 7

Chapter 9

Knowledge Base 6 7

11

Chapter 9

Image Enhancement 6 7

in the Spatial Domain

Contents 6 7

• Spatial Domain

• Point Process

• Transformation functions

• Histogram

• Spatial Filtering

• Image Enhancement

• Smoothing Filter

Chapter 9

Spatiotemporal Signals 6 7

Chapter 9

Image Processing 6 7

• An image processing system maps an input image to an output image

Output images

Input images

Chapter 9

Image Processing 6 7

• Output pixel depends on the input image pixels

• Usually:

Chapter 9

Transformation functions 6 7

1. contrast stretching

2. point processing : Thresholding Function

Transformation function

s= T [r]

Chapter 9

Transformation functions 6 7

light

dark

s

s= T [r]

r

Chapter 9

dark light

Transformation functions 6 7

original image

negative transformation

s= L-1 -r

Chapter 9

Power-Law Transformations 6 7

 = 3

 = 4

 = 5

s= cr

มืดลง

Chapter 9

Contrast Stretching 6 7

Chapter 9

Histogram 6 7

• Count the number of pixels with each gray level

Chapter 9

Histogram 6 7

Chapter 9

Histogram 6 7

Chapter 9

Histogram Equalization 6 7

Chapter 9

Histogram Equalization 6 7

Chapter 9

Histogram Equalization 6 7

Chapter 9

Spatial Filtering 6 7

ค่าน้ำหนัก

ค่าPixels

Chapter 9

Laplacian Output 6 7

Chapter 9

Image Enhancement 6 7

Chapter 9

Image Enhancement 6 7

Chapter 9

Line Detection 6 7

• horizontal,... +45 degree,.. vertical... and -45 degree masks

• Horizontal mask will result with max response when a line passed through the middle row of the mask with a constant background.

• the similar idea is used with other masks.

• note: the preferred direction of each mask is weighted with a larger coefficient ....(i.e.,2)than other possible directions.

Chapter 9

Example 6 7

Chapter 9

Example 6 7

Chapter 9

1). the pixels belonged to one of the set of pixels linked according to the highest count

2). no gaps were longer than 5 pixels

Chapter 9

Result of applying T 6 7

Chapter 9

The End 6 7

Chapter 9