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what is image and graphics

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Title: what is image and graphics


1
Basic Concept Image and Graphics
  • Mr. BIMAL KUMAR RAY
  • DEPT OF I.S.T
  • RAVENSHAW UNIVERSITY

2
What is Image/picture
  • A presentation to the mind in the form of
    an idea or image, mental representation
     or picture idea produced by the imagination.
  • Image is a representation of a real object or
    scene. An image can be viewed on the monitor, on
    printed paper etc.
  • Image a visual representation of
    object or person  produced on a surface
  • Image is also used in place of the
    term digital image, which is an optically formed
    duplicate or other reproduction of an object
    formed by a lens or mirror. 
  • Images may be two-dimensional, such as
    a photograph, screen display, and as well as a
    three-dimensional.
  • Image is a visual representation of something. In
    information technology, the term has several
    usages

3
Images come in many different format
Images can be used to
  • Photographs
  • Paintings
  • Drawings
  • Symbols
  • Corporate logos
  • Maps
  • Diagrams
  • Graphs
  • Explain a process
  • Set a mood
  • Feeling of idea
  • Pinpoint locations
  • Illustrate Relationships
  • Tell stories
  • Compare
  • Identify

4
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5
Graphics/Images
  • Graphics and images are both non-textual
    information that can be displayed and printed.
  • Graphics are normally created in a graphics
    application and internally represented as an
    assembly of objects such as lines, curves,
    rectangle and circles.
  • Attributes such as style, height, width, and
    color define the appearance of graphics.
  • The smallest addressable image element is called
    a pixel.
  • The set of pixels is called a bitmap.
  • Computer graphics two main categories raster
    and vector.

6
  • Raster images are made of pixels.
  • A pixel is a single point or the smallest
    single component in a display device. 
  • Vector images are mathematical calculations from
    one point to another that form geometrical
    shapes.

7
Raster Graphics
  • Raster images are also called Bitmap images.
  • Raster images dimensions are measured in pixels.
  • Raster images cannot be enlarged without losing
    quality.
  • The amount of pixels within each inch in the
    image represents the image pixel resolution or
    ppi (pixels per inch).
  • How large a raster image can be printed - and
    maintain quality - depends on 2 things
  • The pixel dimension of the image (e.g. 6824
    pixels wide by 2345 pixels high)
  • The pixel resolution dots-per-inch (dpi)
    required by the specific printer

8
Vector Graphics
  • Made of mathematical calculations that form
    objects and lines.
  • Vector Can be scaled to any size without losing
    quality.
  • Resolution-independent Can be printed at any
    resolution.
  • Number of colors can be easily increased or
    reduced to adjust printing budget.
  • A large dimension vector graphic can maintain a
    small file size.
  • Vector art is required by many service providers.
  • Vector Can be easily converted to raster.

9
Difference between vector and raster graphics?
  • Raster graphics are composed of pixels, while
    vector graphics are composed of paths.
  • A raster graphic, such as a gif or jpeg, is an
    array of pixels of various colors, which together
    form an image.
  • A vector graphic, such as an .eps file or Adobe
    Illustrator? file, is composed of paths, or
    lines, that are either straight or curved.
  • The data file for a vector image contains the
    points where the paths start and end, how much
    the paths curve, and the colors that either
    border or fill the paths. Because vector graphics
    are not made of pixels, the images can be scaled
    to be very large without losing quality.
  • Raster graphics, on the other hand, become
    "blocky," since each pixel increases in size as
    the image is made larger.

10
Image formation
  • The geometry of image formation, which determines
    where in the image plane the projection of a
    point in the scene will be located.
  • The physics of light, which determines the
    brightness of a point in the image plane as a
    function of illumination and surface properties.
  • Optical parameters of the lens
  • lens type
  • focal length
  • field of view
  • Photometric parameters
  • type, intensity, and direction of illumination
  • Reflection properties of the viewed surfaces
  • Geometric parameters
  • type of projections
  • position and orientation of camera in space
  • perspective distortions introduced by the imaging
    process

11
Digital Image Representation
  • A digital image may be generated by a scanner,
    digital camera.
  • A digital image is a numeric representation
    (normally binary) of a two-dimensional or matrix
    image.
  • Digital image usually refers to raster
    or bitmapped images.
  • A bitmap images take the form of an array, where
    the value of each element, called a pixel.
    (picture element)
  • The pixel values of intensity images are called
    gray scale levels.
  • Each horizontal line in the image is called
    a scan line.
  • The number of horizontal and vertical samples in
    the pixel grid is called Raster dimensions

12
Digital Image Representation
  • Resolution is a measurement of sampling
    density, resolution of bitmap images give a
    relationship between pixel dimensions and
    physical dimensions. 
  • Resolution measurement is ppi, pixels per inch.
  • Megapixels refer to the total number of pixels in
    the captured image, an easier metric is raster
    dimensions which represent the number of
    horizontal and vertical samples in the sampling
    grid.
  • An image with a 43 aspect ratio with dimension
    2048x1536 pixels, contain a total of
    2048x15353,145,728 pixels approximately 3
    million, thus it is a 3 megapixel image.

13
  • If the sampling interval is too large, the
    process by which a digital image was produced may
    be appear to human viewers
  • This is the problem of under sampling
  • Picture Elements Pixel, Color, gray-value images
    and binary images (values 0 for black, 1 for
    white) Example gray-value images contain
    different number of brightness levels

14
Digital images - bit depth The bit depth or
radiometric resolution is the number of bits (0
and 1) used to represent each pixel value. Bits
Range Notes 1
01 Binary image 8
0255 Typical greyscale image 12
04095 High quality
greyscale 16 065535 Very
high quality greyscale 32 (0.0-1.0)
Floating point format 888 3 0255
24 bit True Colour (monitor)
15
1-bit Images
  • File size width x height x BytesPerPixel
  • File size calculation
  • -Resolution 640 x 480
  • -File size 640 x 480 x 1/8 38.4
    kB
  • Each pixel is stored as a single bit (0 or 1), so
    also referred to as binary image.
  • Such an image is also called a 1-bit monochrome
    image since it contains no color.
  • a 1-bit monochrome image (called Lena by
    multimedia scientists this is a standard image
    used to illustrate many algorithms).

16
8-bit Gray-level Images
  • File size calculation
  • Resolution 640 x 480
  • File size 640 x 480 x 1 307200
    300 kB
  • Each pixel has a gray-value between 0 and 255.
    Each pixel is represented by a single byte e.g.,
    a dark pixel might have a value of 10, and a
    bright one might be 230.
  • Bitmap The two-dimensional array of pixel values
    that represents the graphics/image data.
  • Image resolution refers to the number of pixels
    in a digital image (higher resolution always
    produce better quality).
  • - Fairly high resolution for such an image might
    be 1,600 x1,200, whereas lower resolution might
    be 640 x 480.

17
8-bit Color Images
  • Many systems can make use of 8 bits of color
    information (the so-called 256 colors) in
    producing a screen image.
  • Such image files use the concept of a lookup
    table to store color information.
  • Basically, the image stores not color, but
    instead just a set of bytes, each of which is
    actually an index into a table with 3-byte values
    that specify the color for a pixel with that
    lookup table index.
  • 3D histogram of the RGB values of the pixels in
    forest.bmp.
  • Note the great savings in space for 8-bit images,
    over 24-bit ones a 640 x 480 8-bit color image
    only requires 300 kB of storage, compared to
    921.6 kB for a color image .

18
24-bit Color Images
  • In a color 24-bit image, each pixel is
    represented by three bytes, usually representing
    RGB.
  • - This format supports 256 x 256 x 256 possible
    combined colors, or a total of 16,777,216
    possible colors.
  • - However such flexibility does result in a
    storage penalty A 640 x 480 24-bit color image
    would require 921.6 kB of storage without any
    compression.
  • An important point many 24-bit color images are
    actually stored as 32-bit images, with the extra
    byte of data for each pixel used to store an
    alpha value representing special effect
    information (e.g., transparency).
  • the image forest.bmp, a 24-bit image in Microsoft
    Windows BMP format. Also shown are the grayscale
    images for just the Red, Green, and Blue
    channels, for this image.

19
24-bit Color Images
  • In a color 24-bit image, each pixel is
    represented by three bytes, usually representing
    RGB.
  • - This format supports 256 x 256 x 256 possible
    combined colors, or a total of 16,777,216
    possible colors.
  • - However such flexibility does result in a
    storage penalty A 640 x 480 24-bit color image
    would require 921.6 kB of storage without any
    compression.
  • An important point many 24-bit color images are
    actually stored as 32-bit images, with the extra
    byte of data for each pixel used to store an
    alpha value representing special effect
    information (e.g., transparency).
  • the image forest.bmp, a 24-bit image in Microsoft
    Windows BMP format. Also shown are the grayscale
    images for just the Red, Green, and Blue
    channels, for this image.

20
Image Format
  • Image formatting means capturig an image from a
    camera and bringing it into a digital form.
  • A digital representation of an image in the form
    of pixels.
  • There are different kinds of image formats in
    the multimedia.
  • The BMP file format (Windows bitmap) handles
    graphics files within the Microsoft Windows OS.
    Typically, BMP files are uncompressed, and
    therefore large their advantage is their simple
    structure and wide acceptance in Windows
    programs.

21
Image Format
  • JPEG stands for Joint Photographic Experts
    Group, which created this standard for this type
    of image formatting.
  • JPEG files are images that have been compressed
    to store a lot of information in a small-size
    file.
  • A JPEG is compressed in a way that loses some of
    the image detail during the compression in order
    to make the file small. (lossy compression).
  • JPEG files are usually used for photographs on
    the web, because they create a small file that is
    easily loaded on a web page and also looks good.

22
Image Format
  • TIFF stands for Tagged Image File Format. TIFF
    images create very large file sizes.
  • TIFF images are uncompressed and thus contain a
    lot of detailed image data (which is why the
    files are so big) TIFFs are also extremely
    flexible in terms of color (they can be
    grayscale, or CMYK for print, or RGB for web) and
    content (layers, image tags).
  • TIFF is the most common file type used in photo
    software (such as Photoshop), as well as page
    layout software (such as Quark and InDesign),
    again because a TIFF contains a lot of image
    data.

23
Image Format
  • GIF stands for Graphic Interchange Format. This
    format compresses images but, as different from
    JPEG, the compression is lossless.
  • GIFs also have an extremely limited color range
    suitable for the web but not for printing.
  • This format is never used for photography,
    because of the limited number of colors.
  • GIFs can also be used for animations.

24
Image Format
  •  PNG Portable Network Graphics file format was
    created as a free, open-source alternative to
    GIF.
  • The PNG file format supports 8 bit paletted
    images (with optional transparency for all
    palette colors) and 24 bit truecolor (16 million
    colors) or 48 bit truecolor with and without
    alpha channel - while GIF supports only 256
    colors and a single transparent color.
  • PNG is still well-suited to storing images during
    the editing process because of its lossless
    compression.
  • PNG is designed to work well in online viewing
    applications like web browsers and can be fully
    streamed with a progressive display option.

25
Image Format
  • Raw image files contain data from a digital
    camera and photoshop etc.
  • The files are called raw because they have not
    been processed and therefore cant be edited or
    printed yet.
  • There are a lot of different raw formats each
    camera company often has its own proprietary
    format.
  • Raw files usually contain a vast amount of data
    that is uncompressed. Because of this, the size
    of a raw file is extremely large. Usually they
    are converted to TIFF before editing and
    color-correcting.

26
Image Format
  • DIB Microsoft Windows bitmap image file
  • EPS Adobe Encapsulated PostScript file
  • EPSF Adobe Encapsulated PostScript file
  • EPSI Adobe Encapsulated PostScript Interchange
    format
  • JBIG Joint Bi-level Image experts Group file
    interchange format
  • PBM Portable Bitmap format (black and white)
  • PDF Portable Document Format
  • PGM Portable Graymap format (gray scale)
  • PS Adobe PostScript file
  • PSD Photoshop Document
  • SVG Scalable Vector Graphics.
  • RIFF Resource Interchange File Format

27
Graphics File Format
  • There are a number of different types of graphics
    file formats. Each type stores graphics data in a
    different way. Bitmap, vector, and metafile
    formats are by far the most commonly used
    formats, there are other types of formats as
    well--scene, animation, multimedia, hybrid,
    hypertext, hypermedia, 3D, virtual modeling
    reality language (VRML), and page description
    language (PDL).
  • Vector format files are particularly useful for
    storing line-based elements, such as lines and
    polygons, or those that can be decomposed into
    simple geometric objects, such as text.
  • Vector files contain mathematical descriptions of
    image elements, rather than pixel values. A
    rendering application uses these mathematical
    descriptions of graphical shapes (e.g., lines,
    curves, and splines) to construct a final image.
  • Graphics format file- .dir, .fla, .flc, .fli,
    .gif, .ppt, .dgi, .wmf, X3D, .3D, .3DF, .3DM,
    .3ds  etc.

28
What is Image Processing?
  • Image processing is a method to convert an image
    into digital form and perform some operations. To
    get an enhanced image or to extract some useful
    information from.
  • Importing the image with optical scanner or by
    digital photography.
  • Image Processing system includes treating image
    converse process the analysis of scence, or the
    reconstruction of models from pictures of 2/3D
    objects.
  •  Analyzing and manipulating the image which
    includes data compression and image enhancement
    and spotting patterns that are not to human eyes
    like satellite photographs.
  • Output is the last stage in which result can be
    altered image or report that is based on image
    analysis.

29
Image Processing Criteria
  • The two types of methods used for Image
    Processing are Analog and Digital Image
    Processing.
  • Analog or visual techniques of image processing
    can be used for the hard copies like printouts
    and photographs.
  • Digital Processing techniques help in
    manipulation of the digital images by using
    computers.
  • The purpose of image processing is divided into 5
    groups. They are
  • Visualization Observe the objects that are not
    visible.
  • Image sharpening and restoration To create a
    better image.
  • Image retrieval Seek for the image of interest.
  • Measurement of pattern Measures various objects
    in an image.
  • Image Recognition Distinguish the objects in an
    image

30
Image Synthesis (generation/creation)
  • The pictorial systhesis of real or imaginary
    objects from their computer- based models.
  • Image Synthesis refers to processing of a 2D/3D
    picture by a computer.
  • Combination of text with document recognition,
    image enhancement, image synthesis and image
    reconstruction.
  • Creation of the original picture (geometric
    representation, rotation, surface model)
  • User Interface shape change (correction in
    3-dimensions, size.color etc)
  • Image display (display in 3-dimensions, light
    source, shading, filtering and other adjustments)
  • This processing technique may be, Image
    enhancement, Image restoration, and Image
    compression.

31
Color Image Data Types
  • The most common data types for graphics and image
    file formats 24-bit color and 8-bit color.
  • Some formats are restricted to particular
    hardware / operating system platforms, while
    others are cross-platform formats.
  • Even if some formats are not cross-platform,
    there are conversion applications that will
    recognize and translate formats from one system
    to another.
  • Most image formats incorporate some variation of
    a compression technique due to the large storage
    size of image files. Compression techniques can
    be classified into either lossless or lossy.

32
Dithering
  • Dithering is used to calculate patterns of dots
    such that values from 0 to 255 correspond to
    patterns that are more and more filled at darker
    pixel values, for printing on a 1-bit printer.
  • Mixing of colors, merging of pixels of different
    colors to create an area of intermediate color.
  • For printing
  • The main strategy is to replace a pixel value by
    a larger pattern, say 2 x 2 or 4 x 4, such that
    the number of printed dots approximates the
    varying-sized disks of ink used in analog, in
    halftone printing (e.g., for newspaper photos).
  • Half-tone printing is an analog process that uses
    smaller or larger filled circles of black ink to
    represent shading, for newspaper printing.
  • For example, if we use a 2 X 2 dither matrix

33
Image Analysis (recognition)
  • Image analysis is techniques for extract
    descriptions from images that are necessary for
    higher- level scene analysis methods.
  • Image enhancement
  • contrast to make a graphic display more useful
    for display analysis.
  • It includes gray level contrast manipulation,
    noise reduction, edge sharpening, filtering,
    coloring,
  • Image Recognition
  • Image formatting means capturing an image from
    a camera and bringing it into a digital form.
  • Digital representation of an image in the form
    of pixels.
  • Preparing and transforming the image
  • Labeling, Grouping, Matching, Extracting and
    Conditioning for image
  • Image restoration image to minimize the effect
    of degradations. (Filter Effects)
  • Image compression minimizing the number of bits
    required to represent an image.

34
Image Transmission
  • Transmission of digital images through
    computer networks, Internet etc.
  • Image size depends on the image representation
    format used for transmission.
  • Raw image data transmission
  • Compressed image data transmission
  • Symbolic image data transmission
  • Image size is equal to the structure size,
    which carries the transmitted symbolic
    information of the image.
  • Examples the transmission of an image with a
    resolution of 640 x 480 pixels and pixel
    quantization of 8 bits per pixel requires
    transmission of 307,200 bytes through the network.

35
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