what is image and graphics

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Basic Concept Image and Graphics

• Mr. BIMAL KUMAR RAY
• DEPT OF I.S.T
• RAVENSHAW UNIVERSITY

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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

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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

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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.

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• 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.

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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

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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.

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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.

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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

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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

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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.

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• 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

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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)
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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).

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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.

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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 .

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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

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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.

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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.

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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

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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.

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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.

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