md. monjur –ul-hasan department of computer science & engineering chittagong university of...
TRANSCRIPT
Md. Monjur –ul-Hasan
Department of Computer Science & Engineering
Chittagong University of Engineering & Technology
Chittagong 4349http://monjur-ul-hasan.info
IMAGES AND GRAPHICS
A digital image is a representation of a two-dimensional image as a finite set of digital values, called picture elements or pixels
•Pixel values typically represent gray levels, colours, heights, opacities etc•Remember digitization implies that a digital image is an approximation of a real scene
Pixel
1 pixel
Image Format
•Common image formats include:▫1 sample per point (B&W or Grayscale)▫3 samples per point (Red, Green, and Blue)▫4 samples per point (Red, Green, Blue, and
“Alpha”, a.k.a. Opacity)
•For most of this course we will focus on grey-scale images
Image Format
Bitmap: An array of information that contains the information for the image.
It is a 3 dimensional arrayWidth x Height x 24 (8 for each color)So can be huge(.bmp and .tif or .tiff are most common bitmaps)
JPG (Joint-Photographic Experts Group)• Generally better for images and photos• Spatial not color compression, can distort image spatially
and more loss with each save• Now can animate as well.• For continuous tone images, such as full-color photographs• Supports more than 16 millions of color (24-bit)• Uses lossy compression (averaging may lose information)
Image Format
GIF (Graphical Interchange Format)
For large areas of the same color and a moderate level of detail.Supports up to 256 colorsAllows transparency and interlacingUses lossless compression
PNG (Portable Network Graphic)lossless, portable, well-compressed storage of raster
imagespatent-free replacement for GIF also replace many common uses of TIFFSupport indexed-color, grayscale, and true color images +
an optional alpha channel for transparency
Image Format
•Monochrome just requires one bit per pixel, representing black or white
BMP – 16 KB
•8 bits per pixel allows 256 distinct colors
BMP – 119KB
• 16 bits per pixel represents 32K distinct colors (Most graphic chipsets now supports the full 65536 colors and the color green uses the extra one bit)
BMP – 234 KB
• 24 bits per pixel allows millions of colors
• 32 bits per pixel – trillion of colors
BMP – 350KB
Bitmapped vs. JPEG File Sizes
Both images are the same relative size.
900kb
.JPEG High Quality ~700kb
Graphics
•Computer generated or drawn by you.•Specified through graphics primitives
(Lines, Rectangle, circle etc) and their attribute (Line style, width, color etc).
•Not represent by pixel matrix.•You can directly manipulate the
elements because you drew them – Sprites
•Additional conversion is required for Draw pixel matrix.
Graphics Vs Images• Basic element
▫Specified through graphics primitives (Lines, Rectangle, circle etc) and their attribute (Line style, width, color etc).
▫Pixel• Manipulation
▫You can directly manipulate the elements because you drew them – Sprites
▫ In an image, you can manipulate pixels but not directly the elements. This has a great impact.
• Visible▫Additional conversion is required for Draw
pixel matrix.▫No Conversion required
Dynamic In Graphics
•Motion Dynamics▫Object can be moved and enabled with
respect to the stationary object.▫Both the object and the camera are
moving. •Update Dynamics
▫Change the shape, colour, or other properties of the objects being viewed.
Graphics Hardware
•Architecture of Raster Display
Minimum refresh rate 60 Hz is used to avoid flickering
Screen Mosaic Triad Arrangement
Interlaced Projection
Dithering
• Dithering▫ If we view a very small area from a sufficiently large
viewing distance, our eyes average fine detail within the small area and record only the overall intensity of the area.
▫ This phenomenon used in hardware display is known as dithering
▫ Color display with three bits per pixel: red, green, blue▫ 2X2 pattern area▫ It can produce 5X5X5 color combinations
Digital Image Processing
•Digital image processing focuses on two major tasks
▫Improvement of pictorial information for human interpretation
▫Processing of image data for storage, transmission and representation for autonomous machine perception
•Some argument about where image processing ends and fields such as image analysis and computer vision start
•Computer image processing• Image synthesis (generation)• Image analysis (recognition)
•Image synthesis• Pictorial synthesis of real or imaginary
objects• Mainly graphics concern with synthesis
•Image analysis• Recognition of models from pictures of 2D
or 3D objects
Digital Image Processing (DIP)
Digital Image Processing(DIP)
Low Level Process
Input: ImageOutput: Image
Examples: Noise removal, image sharpening
Mid Level Process
Input: Image Output: Attributes
Examples: Object recognition, segmentation
High Level ProcessInput: Attributes Output: Understanding
Examples: Scene understanding, autonomous navigation
•The continuum from image processing to computer vision can be broken up into low, mid- and high-level processes
Digital Image Processing(DIP)
Image Acquisition
Image Restoration
Morphological
Processing
Segmentation
Representation &
Description
Image Enhancemen
t
Object Recognition
Problem Domain
Colour Image
Processing
Image Compression
Image Acquisition
Image Restoration
Morphological
Processing
Segmentation
Representation &
Description
Image Enhancemen
t
Object Recognition
Problem Domain
Colour Image
Processing
Image Compression
Image Acquisition
Image Restoration
Morphological
Processing
Segmentation
Representation &
Description
Image Enhancemen
t
Object Recognition
Problem Domain
Colour Image
Processing
Image Compression
Image Acquisition
Image Restoration
Morphological
Processing
Segmentation
Representation &
Description
Image Enhancemen
t
Object Recognition
Problem Domain
Colour Image
Processing
Image Compression
Image Acquisition
Image Restoration
Morphological
Processing
Segmentation
Representation &
Description
Image Enhancemen
t
Object Recognition
Problem Domain
Colour Image
Processing
Image Compression
Image Acquisition
Image Restoration
Morphological
Processing
Segmentation
Representation &
Description
Image Enhancemen
t
Object Recognition
Problem Domain
Colour Image
Processing
Image Compression
Image Acquisition
Image Restoration
Morphological
Processing
Segmentation
Representation &
Description
Image Enhancemen
t
Object Recognition
Problem Domain
Colour Image
Processing
Image Compression
Image Acquisition
Image Restoration
Morphological
Processing
Segmentation
Representation &
Description
Image Enhancemen
t
Object Recognition
Problem Domain
Colour Image
Processing
Image Compression
Image Acquisition
Image Restoration
Morphological
Processing
Segmentation
Representation &
Description
Image Enhancemen
t
Object Recognition
Problem Domain
Colour Image
Processing
Image Compression
Image Acquisition
Image Restoration
Morphological
Processing
Segmentation
Representation &
Description
Image Enhancemen
t
Object Recognition
Problem Domain
Colour Image
Processing
Image Compression
Image Recognition Steps
Steps:
Formatting
Conditionin
g
Labeling
Grouping
Extracting
Matching
Image Recognition Steps
ConditioningSuppresses noiseBackground normalization
By suppressing uninteresting systematic or pattern variations
LabelingInformative pattern has structure with set of connected pixels.
Region, edge
GroupingThe grouping operation identifies the events by collecting together or identifying maximal connected sets of pixels participating in the same kind of event.Example: Edges are grouped into lines, is called line-fitting
Image Recognition Steps
ExtractingExtracting operation computes for each group of pixels a list of properties.Example:
CentroidAreaOrientationSpatial moments, gray tone moments, spatial-gray tone momentsCircumscribing circle, inscribing circle,
MatchingDetermines the interpretation of some related set of image events, associating these events with some given three-dimensional object or two-dimensional shape.Example: Template matching
Image Transmission
Raw Image TransmissionSize = spatial resolution X pixel quantization
Compressed image data transmission
JPEG, MPEG
Symbolic image data transformationimage primitive, attribute etc.
Thank You All