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Introduction to compression techniques


Introduction to compression techniques,Vector Graphics and Raster Graphics Difference,Compare and Contrast Vector Vs Raster?

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									                          Compare and Contrast Vector Vs Raster?

In computer graphics, a raster graphics image, or bitmap, is a data structure representing a
generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other
display medium. Raster images are stored in image files with varying formats (see
Comparison of graphics file formats).

A bitmap corresponds bit-for-bit with an image displayed on a screen, generally in the same
format used for storage in the display's video memory, or maybe as a device-independent
bitmap. Vector graphics is the use of geometrical primitives such as points, lines, curves, and
shapes or polygon(s), which are all based on mathematical expressions, to represent images
in computer graphics. "Vector", in this context, implies more than a straight line.

Vector graphics is based on images made up of vectors (also called paths, or strokes) which
lead through locations called control points. Each of these points has a definite position on
the x and y axes of the work plan. Each point, as well, is a variety of database, including the
location of the point in the work space and the direction of the vector (which is what defines
the direction of the track).

There are instances when working with vector tools and formats is the best practice, and
instances when working with raster tools and formats is the best practice. There are times
when both formats come together.
     Vector Graphics and Raster Graphics Difference

     Word processors and spreadsheet or presentation applications, although suitable for
     creating files for office or Internet use, are not recommended for creating digital art for print.
     Microsoft Office applications are included in this group. In some cases, however, such files
     may be converted so as to enable use.

Compare                                             Types of Images
Categorizes                    Vector Images                       Raster/Bitmap Images
                       Vector graphics are resolution      Raster graphics are resolution
                        independent.                           dependent.

                       They can be scaled up or down
                        without any loss of quality.            They cannot be enlarged without
                                                                 losing image quality.
                       Vector images are defined by
                        math, not pixels.                       The resolution of a raster image or
                                                                 scanned image is expressed in terms
                                                                 of the dots per inch or dpi.
                       Vector images are composed of           Raster images are composed of
                        objects not pixels.                      pixel, so color of each Dots or
                       Easier to change the color of
                        individual objects without         complexity of colors and try to
                        worrying about individual pixels.   change colors, and you can see the
                                                            biggest disadvantage of editing and
                       Coloring vector images is much      manipulating raster images
                        easier than coloring bitmaps.

                       Common Vector image formats :           Common raster image formats :
                        EPS (Encapsulated PostScript)            BMP (Windows Bitmap)
                        WMF (Windows Metafile)                   PCX (Paintbrush)
                        AI (Adobe Illustrator)                   TIFF (Tag Interleave Format)
       File             CDR (CorelDraw)                          JPEG (Joint Photographics Expert
       Formats          DXF (AutoCAD)                            Group) GIF (Graphics Interchange
                        SVG (Scalable Vector Graphics)           Format)
                        PLT (Hewlett Packard Graphics            PNG (Portable Network Graphic)
                        Language Plot File)                      PSD (Adobe PhotoShop)
                                                                 CPT (Corel PhotoPAINT)
                       Popular Vector Editing                  Popular Bitmap Editing Programs :
                        Programs :                               Adobe Photoshop
                        Adobe Illustrator                        GIMP
                        CorelDRAW                                Microsoft Paint
                        Freehand                                 Corel PhotoPAINT
                        Serif DrawPlus
                        Xara Xtreme
2.E-Mail the One Page Description About Compression Technique?

Introduction to compression techniques

Compression is the reduction in size of data in order to save space or transmission time. For data
transmission, compression can be performed on just the data content or on the entire transmission unit
(including header data) depending on a number of factors.

JPEG, Motion JPEG and MPEG are three well-used acronyms used to describe different types of image
compression format. But what do they mean, and why are they so relevant to today’s rapidly expanding
surveillance market? This White Paper describes the differences, and aims to provide a few answers as
to why they are so important and for which surveillance applications they are suitable.

When an ordinary analog video sequence is digitized according to the standard CCIR 601, it can
consume as much as 165 Mbps, which is 165 million bits every second. With most surveillance
applications infrequently having to share the network with other data intensive applications, this is very
rarely the bandwidth available. To circumvent this problem, a series of techniques – called picture and
video compression techniques – have been derived to reduce this high bit-rate. Their ability to perform
this task is quantified by the compression ratio. The higher the compression ratio is, the smaller is the

The basics of compression
Compression basically means reducing image data. As mentioned previously, a digitized analog video
sequence can comprise of up to 165 Mbps of data. To reduce the media overheads for distributing these
sequences, the following techniques are commonly employed to achieve desirable reductions in image
> Reduce color nuances within the image
> Reduce the color resolution with respect to the prevailing light intensity
> Remove small, invisible parts, of the picture
> Compare adjacent images and remove details that are unchnaged between two images

The first three are image based compression techniques, where only one frame is evaluated and
compressed at a time. The last one is or video compression technique where different adjacent frames
are compared as a way to further reduced the image data.

As a result of these subtle reductions, a significant reduction in the resultant file size for the image
sequences is achievable with little or no adverse effect in their visual quality. The extent, to which these
image modifications are humanly visible, is typically dependent upon the degree to which the chosen
compression technique is used. Often 50% to 90% compression can be achieved with no visible
difference, and in some scenarios even beyond 95%.

Compression involves one or several mathematical algorithms that remove image data. When the video
is to be viewed other algorithms are applied to interpret the data and view it on the monitor. Those steps
will take a certain amount of time. That delay is called compression latency. The more advanced
compression algorithm, the higher the latency. When using video compression and several adjacent
frames are being compared in the compression algorithm, more latency is introduced.
For some applications, like compression of studio movies, compression latency is irrelevant since the
video is not watched live. In surveillance and security using live monitoring, especially when PTZ and
dome cameras are being used, low latency is essential.
3.Prepare the Table for File Types Including Relevant Details as Shot Name of
Extension ,Descriptor of Extension, Compression Types and Proprietorship?

     Details as Shot Name of          Descriptor of Extension                         Compression Types and
            Extension                                                                      Proprietorship

              (JPEG)                JPG is optimized for photographs and
    Joint Photographic Experts      similar continuous tone images that
                                    contain many, many colors. It can              Lossy Compression
              Group                 achieve astounding compression ratios
                                    even while maintaining very high image

                (TGA)               All values are little-endian; field and
               TARGA                subfield numbers are per Version 2.0
                                    of the specification.
                                    Version 2 added the extension area and
                                                                                   Raster image file
                                    footer. The developer area exists to
                                    store application-specific information

             (TIFF)                  It is, in principle, a very flexible format
                                    that can be lossless or lossy. The
    Tagged Image File Format        details of the image storage algorithm         Lossy Compression
                                    are included as part of the file.

              (PNG)                 This page is intended to provide an
                                    explanation of some of the features of
         Portable Network           the PNG format for non-technical users.
             Graphics                                                              Lossless data Compression
                                    As such, it doesn't emphasize PNG
                                    features like freedom from patents;
                                    those are more of concern to

               (BMP)                The simplicity of the BMP file format,
                                    and its widespread familiarity in
               Bitmap               Windows and elsewhere, as well as the
                                    fact that this format is relatively
                                    well documented and free of patents,
                                    makes it a very common format that             Lossless data compression
                                    image processing programs from many
                                    operating systems can read and write.
             (GIF)                   GIF is the abbreviation of Graphics
                                    Interchange Format. It was originally          Lossless data compression
      Graphics Interchange          developed by CompuServe (an on-line
            Format                  service that was pretty successful in the
                                    early nineties).

             ( PICT)                PICT is a graphics file
                                    format introduced on the original Apple
   :Parliamentary Information       Macintosh computer as its
      and Communication             standard metafile format. It allows the
           Technology               interchange of graphics
                                    (both bitmapped and vector), and some          :both bitmapped and vector
                                    limited text support, between Mac
                                    applications, and was the native
                                    graphics format of QuickDraw.

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