Image Processing Ch 1 Introduction Prepared by Hanan

Image Processing Ch 1: Introduction Prepared by: Hanan Hardan

Introduction “One picture is worth more than ten thousand words”

References “Digital Image Processing”, Rafael C. Gonzalez & Richard E. Woods, Addison-Wesley, 2002 p n Much of the material that follows is taken from this book “Machine Vision: Automated Visual Inspection and Robot Vision”, David Vernon, Prentice Hall, 1991 n Available online at: homepages. inf. ed. ac. uk/rbf/BOOKS/VERNON/

Contents p. This n n n lecture will cover: What is a digital image? What is digital image processing? History of digital image processing State of the art examples of digital image processing Key stages in digital image processing

What is a Digital Image? p. A digital image: is a representation of a two-dimensional image as a finite set of digital values, called picture elements or pixels

What is a Digital Image? (cont…) p Pixels: Elements of the digital image , each has intensity. p Intensity of pixel: the amplitude ﻏﺰﺍﺭﺓ of gray level (in gray scale images) 1 pixel

digital image processing What is digital Image? An image can be defined as function of 2 variables , f(x, y), where x and y are spatial coordinates, and the amplitude of f at any pair of coordinates (x , y) is called the intensity of the image at that point p Digital image is composed of a finite number of elements, each one has a particular location and value. . These element are called picture elements, image elements or pixels. Note: images can be: binary, grayscale, color. p

What is digital Image?

digital image processing The image consists of finite number of pixels ( f(x, y) ) What is digital image? Every pixel Is an intersection ﺗﻘﺎﻃﻊ between a row and a column. every pixel has intensity ﻛﺜﺎﻓﺔ pixel Ex: f(4, 3)= 123 Refers to a pixel existing on the intersection between row 4 with column 3, and its intensity is 123. Remember digitization implies that a digital image is an approximation of a real scene

digital image processing Remember: images can be: binary, grayscale, color. Binary Images Binary images are images that have been quantized to two values, usually denoted 0 and 1, but often with pixel values 0 and 255, representing black and white.

Binary Images

Grayscale Images p A grayscale (or graylevel) image is simply one in which the only colors are shades of gray (0 – 255)

Grayscale Images

Color Images p Color image: A color image contains pixels each of which holds three intensity values corresponding to the red, green, and blue or( RGB)

Color Images

digital image processing What is digital image processing? p Digital image processing focuses on two major tasks n n Improve image quality(pictorial information) for human perception and interpretation Processing of image data for storage, transmission and representation for autonomous machine perception

Image processing fields: 1. 2. 3. Computer Graphics: the creation of image Image processing: enhancement or other manipulation of the image Computer vision: analysis of the content

digital image processing What are digital image processing levels? p low level processes: n n Input and output are images Tasks: Primitive operations, such as, image processing to reduce noise, contrast enhancement and image sharpening ﻣﺜﺎﻝ ﺻﻮﺭﺓ ﻗﺪﻳﻤﺔ ﻧﺮﻳﺪ ﺗﺤﺴﻴﻨﻬﺎ

What are digital image processing levels? p Mid-Level Processes: n Inputs, generally, are images. Outputs are attributes extracted from those images (edges, contours, identity of individual objects) n Tasks: Segmentation (partitioning an image into regions or objects) p Description of those objects to reduce them to a form suitable for computer processing p Classifications (recognition) of objects p ﺻﻮﺭﺓ ﻟﻜﺮﺳﻲ ﻧﺮﻳﺪ ﺗﻌﺪﻳﻠﻬﺎ ﺣﺎﺳﻮﺑﻴﺎ ﻟﻨﺒﺮﺯ ﺣﻮﺍﻓﻪ : ﻣﺜﺎﻝ

What are digital image processing levels? p High-Level Processes p Input: Attributes Output: Understanding p Tasks: recognizing objects n Image analysis and computer vision(Analysis of the image content) p Examples: Scene understanding ﺻﻮﺭﺓ ﻟﻤﺸﺘﺒﻪ ﻓﻴﻪ ﻧﺮﻳﺪ ﺍﻟﺤﺎﺳﻮﺏ ﺍﻥ ﻳﺘﻌﺮﻑ ﻋﻠﻴﻪ : ﻣﺜﺎﻝ

Uses of DIP n n n Image enhancement/restoration Artistic effects Medical visualisation Law enforcement Human computer interfaces

Examples: Image Enhancement p One of the most common uses of DIP techniques: improve quality, remove noise etc

Examples: The Hubble Telescope p. Launched in 1990 the Hubble telescope can take images of very distant objects p. However, an incorrect mirror made many of Hubble’s images useless p. Image processing techniques were used to fix this

Examples: Artistic Effects p Artistic effects are used to make images more visually appealing, to add special effects and to make composite images

Examples: Medicine Take slice from MRI (Magnetic Resounance Imaging) scan of a heart, and find boundaries between types of tissue n Image with gray levels representing tissue density n Use a suitable filter to highlight edges

Examples: GIS p. Geographic n n n Information Systems Digital image processing techniques are used extensively to manipulate satellite imagery Terrain classification ( )ﺍﻟﺘﻀﺎﺭﻳﺲ Meteorology ( )ﺍﻷﺮﺻﺎﺩ ﺍﻟﺠﻮﻳﺔ

Examples: Law Enforcement p. Image processing techniques are used extensively by law enforcers n Number plate recognition for speed cameras n Fingerprint recognition

Examples: HCI p. Try to make human computer interfaces more natural n Face recognition

Fundamental steps in digital image processing

1. Image Acquisition: (capturing an image in digital form) Image Restoration Morphologic al Processing Image Enhancemen t Segmentatio n Image Acquisition Object Recognition Problem Domain Colour Image Processing Image Compression Representatio n& Description

Fundamental Steps in DIP Step 1: Image Acquisition The image is captured by a sensor (eg. Camera), and digitized if the output of the camera or sensor is not already in digital form, using analogue-to-digital convertor

2. Image Enhancement: making an image look better in a subjective way. Image Restoration Morphologic al Processing Image Enhancemen t Segmentatio n Image Acquisition Object Recognition Problem Domain Colour Image Processing Image Compression Representatio n& Description

Fundamental Steps in DIP Step 2: Image Enhancement p The process of manipulating an image so that the result is more suitable than the original for specific applications. p Enhancement techniques are so varied, and use so many different image processing approaches p The idea behind enhancement techniques is to bring out details that are hidden, or simple to highlight certain features of interest in an image.

3. Image Restoration: improving the appearance of any image objectively. Image Restoration Morphologic al Processing Image Enhancemen t Segmentatio n Image Acquisition Object Recognition Problem Domain Colour Image Processing Image Compression Representatio n& Description

Fundamental Steps in DIP Step 3: Image Restoration - Improving the appearance of an image ( )ﻣﺤﺎﻭﻟﺔ ﺍﻋﺎﺩﺓ ﺍﻟﺼﻮﺭﻩ ﺍﻟﻰ ﻃﺒﻴﻌﺘﻬﺎ - Tend to be based on mathematical or probabilistic models of image degradation.

4. Morphological Processing: extracting image components that are useful in the representation and description of shape Image Restoration Morphologic al Processing Image Enhancemen t Segmentatio n Image Acquisition Object Recognition Problem Domain Colour Image Processing Image Compression Representatio n& Description

Fundamental Steps in DIP Step 4 : Morphological Processing Tools for extracting image components that are useful in the representation and description of shape.

5. Segmentation: partitioning an image into its constituent parts or objects. Image Restoration Morphological Processing Image Enhancemen t Segmentation Image Acquisition Object Recognition Problem Domain Colour Image Processing Image Compression Representatio n& Description

Fundamental Steps in DIP Step 5: Image Segmentation procedures partition an image into its parts or objects. Computer tries to separate objects from the image background. ﺍﻟﺤﺼﻮﻝ ﻋﻠﻰ ﺍﻻﺟﺰﺍﺀ ﺍﻟﻤﻬﻤﻪ ﺍﻭ ﻻﻋﺎﺩﺓ ﺗﺸﻜﻴﻞ ﺍﻟﺼﻮﺭﺓ ﻟﺘﻌﻄﻲ ﻣﻌﻨﻰ : ﺍﻟﻬﺪﻑ ﻣﺨﺘﻠﻒ

6. Object Recognition: assigning a label to an object based on its descriptors Image Restoration Morphologic al Processing Image Enhancemen t Segmentatio n Image Acquisition Object Recognition Problem Domain Colour Image Processing Image Compression Representatio n& Description

Fundamental Steps in DIP Step 6 : Recognition and Interpretation Recognition: the process that assigns label to an object based on the information provided by its description. ﺗﻤﻴﺰ ﻣﺤﺘﻮﻯ ﺍﻟﺼﻮﺭﻩ

7. Representation & Description: boundary representation vs. region representation. Boundary descriptors vs. region descriptors Image Restoration Morphologic al Processing Image Enhancemen t Segmentatio n Image Acquisition Object Recognition Problem Domain Colour Image Processing Image Compression Representatio n& Description

Fundamental Steps in DIP Step 7: Representation and Description Make a decision whether the data should be represented as a boundary or as a complete region: p Boundary representation: focus on external shape characteristics, such as corners and inflections. p Region representation: focus on internal properties, such as texture or skeleton shape ﺗﻤﺜﻴﻞ ﺍﻟﺼﻮﺭﻩ ﻭﻭﺻﻔﻬﺎ

8. Image Compression: reducing the stored and transmitted image data. Image Restoration Morphologic al Processing Image Enhancemen t Segmentatio n Image Acquisition Object Recognition Problem Domain Colour Image Processing Image Compression Representatio n& Description

Fundamental Steps in DIP Step 8: Compression Techniques for reducing the storage required to save an image or the bandwidth required to transmit it.

9. Colour Image Processing: color models and basic color processing Image Restoration Morphologic al Processing Image Enhancemen t Segmentatio n Image Acquisition Object Recognition Problem Domain Colour Image Processing Image Compression Representatio n& Description

Fundamental Steps in DIP Step 9: Colour Image Processing Use the colour of the image to extract features of interest in an image