2. Graphics
1. Elements of Graphics
1.1 Pictures and Images
1.2 Raster or Bitmap Images
1.3 Vector Images
2. Image and Color
2.1 Computer Display Resolution
2.2 Computer-Generated Color
2.3 Color Palettes and Color Look-up Tables
2.4 Color Dithering
2.5 Color Flashing
3. Graphics files and application formats
3.1 Bitmap Formats
3.2 Vector Formats
3.3 Compressed Formats
3.4 Proprietary Formats
3. 4. Obtaining images for multimedia use
4.1 Paint and Drawing Applications
4.2 Scanners
4.3 Video and Image Digitizers
4.4 Digital Cameras
5. Using graphics in Applications
5.1 Selecting Graphics for Multimedia
5.2 Backgrounds and Transitions
5.3 Information Delivery
5.4 Navigation
4. 1. Elements of Graphics
Computer-Based graphics, like primitive cave drawings, are
used to transmit messages or make statements of importance to
both the sender and receiver.
There are as many types of pictures as there as ideas on how to
convey them:
• Pictures of people, places and things
• Diagrams of buildings and equipment
• Charts and graphs where figures are depicted
through lines, curves, and color
5. 1.1 Pictures and Images:
Two levels of abstraction or graphics: Pictures and
images.
Pictures are found in the world external to the computer
while images are the two-dimensional representations of
pictures found in computers.
The only advantages is that it is much easier to store and
process in a computer because it already resides there.
There are two basic strategies applied when putting
pictures in the computer.
1. Raster or bitmap images
2. Vector or metafile images
6. 1.2 Raster or Bitmap Images
The most common and comprehensive form of storage for
images on a computer is as a raster or bitmap image.
The terms raster and bitmap can be used interchangeably
as they refer to images that are created as two-dimensional
sets of points on a computer display.
Depending on the hardware capabilities, each point can
display from two to millions of colors.
A raster or bitmap image is composed of a matrix of
elements called pixels. Each pixels consists of two or more
colors. The color depth is determined by how much data, in
bits, is used to determine the number of colors,
For ex: 1 bit yields 2 colors.
4 bits yields 16 colors.
7. 1.3 Vector Images
Vector images are based on drawing elements or objects
such as lines, rectangles, circles, and so forth to create an
image.
Vector images are actually stored as a series of commands
that define the individual objects.
Line: line x1,y1,x2,y2,color
Rectangle: rectangle top,left,width,height,color
Circle: circle top,left,radius,color
Vector images are created by larger objects(squares, circles,
polygons)that can be proportionately resized without losing the
integrity of the original image.
The advantage of a vector image is the relatively small
amount of data required to represent the image and therefore it
does not require a lot o memory to store
8. 2. Images and Color:
Computer image color ranges from simple black and white
to millions of colors.
Systems that support the display of over 16 million colors.
The use of color in multimedia depends on two factors.
1. The subject or content of the image
2. The technical capability of the computer hardware
and software.
Computer color is based on adjusting combinations of
additive colors: red,green,and blue(RGB). Combining these
colors yields a basic set of working colors:
Red+Green+Blue=White
Green+Red=Yellow
Blue+Red=Magenta
No color=Black
9. 2.1 Computer Display Resolution:
Computer display resolution is the number of pixels that
make up the height and width of the display presented by the
computer monitor.
graphics capability includes:
• Image size of:
640 by 480 pixels
800 by 600 pixels
1024 by 768 pixels
• Color depth of:
256 colors
32,768 colors
65,536 colors
The ability to display large numbers of pixels and colors is
dependent on the amount of video memory to handle storing
the image display as well as refresh images.
10. 2.2 Computer-Generated Color:
Computer monitors display color by shining an electron
beam off phosphorescent color does(red , green, and blue) at
very high speeds.
The Creation of visible color is a function of three
characteristics: hue, saturation and brightness(HSB) or
lightness(HSL).
• Hue is based on a vector value moving from 0 to
360 degrees on a color wheel.
• Saturation is the intensity of the color in a
percentage scale:100 percent is a pure color, 0
percent is black, white or gray.
• Brightness and lightness are a function of how
much black or white is mixed with the color.
11. 2.3 Color Palettes and Color Look-up Tables:
Computers manage color via palettes or color look-up
tables(CLUT)
Most multimedia systems are based on ranges from 256 to
16 million colors.
The value range of multimedia computers is 0 to 255, for
256 possible hues for each of red,blue, and green for a total of
16,777,216 color combinations.
Red Value Green Value Blue Value Resulting
Color
0 0 0 White
255 255 255 Black
255 0 0 Red
0 0 0 Green
2.3 Color Indexing Table
12. 2.4 Color Dithering
Dithering is the process through which colors are changed
to meet the closest available color based on the available
palette.
The image palette is mapped into the new palette
dimensions with colors substituted with the closest available
values.
The Quality o the dithering will depend on the algorithm
used but most systems provide close approximations of the
original.
An example of dithering is seen in some World Wide Web
browser applications that use a limited palette o colors–
typically 256 or less.
13. 2.5 Color Flashing
Color flashing occurs when images change the basic color
palette.
This happens most often with animation or consecutively
displayed images with different palettes in each successive
image.
When the new image is loaded, the palette is mapped into
the new set of colors and a momentary flashing can be
observed that can be distracting to the viewer.
Color flashing can be resolved by:
• Creating a shared palette; that is, using a common
palette for all images.
• Fading images to black or white, which are common
colors for most palettes.
14. 3. Graphics File and Application Formats
There are large number of graphic file formats available
for storing various type of images.
Graphic file data is often compressed to reduce storage
space and store to satisfy specific vendor requirements.
3.1 Bitmap Formats
Bitmap file formats are one o the most common file formats
or graphics across most computer platforms. Common bitmap
formats include:
• Windows Bitmap(BMP) and Device Independent
Bitmap(DIB).
• Windows Run Length Encoded(RLE) Bitmap.
• Applet Pict.
15. 3.2 Vector Formats
Vector files are common across many operating systems and
a number of vendor specific applications.
The Windows metafile is a common vector type image
which is generated by processing vector commands by graphic
functions in the Windows operating system.
3.3 Compressed Formats
Compression can be used to dramatically reduce the file
size, which can be useful for speeding transmission for
networked applications or to store large number of image.
Compressed images often store images in files as follows:
• File header
• Image data
16. The following are popular formats with widespread acceptance and
use:
Graphics Interchange Format(GIF): developed by
CompuServe for moving images in dial-up situations; it has
become a popular format or use in World Wide Web pages.
Tagged Image File Format(TIFF): very high compression
capability, good or black-and-white images.
Joint Photographic Experts Group (JPEG and JPG): pack a 24-
bit color image into a relatively small file size.
3.4 Proprietary Formats
Many commercial software paint and drawing
packages use proprietary formats for storing graphic images. These
same software packages often support other file formats or importing
and exporting images.
17. 4. Obtaining Images for Multimedia
Multimedia developers have a number of options for
creating images. Each of these applications offers developers the
ability to create images for backgrounds , button and content.
4.1 Paint and Drawing Applications
Paint and Drawing applications include a number of
features such as:
• Creating and editing graphic files
• Free-form drawing, object drawing
• Object creation and manipulation
• Image manipulation including image sizing ,color
level
• Rendering or converting a model, including
lighting, shading , color
18. Most tools can be generally assigned to one o the following
categories:
• Simple/Beginner Tools
• Mid-range Tools
• Professional Development Tools
• Conversion Tools
• Screen Capture
4.2 Scanners
Scanners are quite popular for capturing images from
hard copy sources such as books, magazines, letters,
photographs, and even camera slides
Scanners depend on a bright light source to enhance the
image for capture.
19. Scanners come in three basic varieties:
Hand-held: The scanner is physically moved across the
image by hand
Drum : The image is mechanically moved across the
sensor
Flat-Bed : Similarly to a photocopier, the document is
placed on a window and the scanner is mechanically
moved across the image.
Scanner software comes in two varieties:
1. Standalone applications: the scanner software is a separate
application from the scanner that operates the scanner and manages
the image creation and saving-to-file process
2. Embedded applications: the scanner is operated via program
commands from a secondary applications such as paint and/or drawing
Software program
20. 4.3 Video and Image Digitizers
Video and image digitizers are related to scanners in that
they both capture images from fixed objects such as books and
photographs.
4.4 Digital Cameras
Digital cameras have emerged as a popular means to
capture images and move them directly into the
computer.
Digital cameras include both still and motion types.
21. 5. Using Graphics in Multimedia Applications
Multimedia applications use still images, pictures,
photographs, and line art for a number of reasons ranging from
Aesthetics to information deliver
Most images are crated or obtained from:
• Scratch: The image is drawn by a skilled technician
such as a graphic artist
• Scanning or digitizing: The image is captured from
another medium. Depending on what the original
medium is.
• Clip art: The image is part of a larger collection; clip art
often consists of groupings or collection o mages by
subject that can be incorporated into a project free or at
cost.
22. 5.1 Selecting Graphics for Multimedia
There is a basic strategy to follow when selecting graphics
for multimedia products based on purpose, quality, and cost.
Consider the following basic ideas when using graphics in
multimedia products:
• Purpose: Images used in a multimedia product
should be useful and meaningful to the
application.
• Quality: Any image used in a multimedia
product should reflect the overall quality desired
of the entire product.
• Cost: The cost of a graphic is directly related to
its purpose and quality
23. 5.2 Backgrounds and Transitions
Backgrounds and transition screens provide the color
foundation for everything else that is found in a multimedia
product.
Backgrounds have fairly simple characteristics
• They fill up the available display space
• They complement, but do not overwhelm, content
placed on top of them
• Colors are chosen carefully so as to avoid color or
palette flashing or conflict with other media.
• They are used consistently throughout the
applications
24. 5.3 Information Delivery
Images are used to convey information in multimedia
products.
Graphics for information delivery include:
• Drawn images
• Charts and graphs
• Maps
• Scenery
• People
In each case, the image must be relevant to the overall
product. Image size, color in respect to the application and other
images, and positioning must all be considered when using
images.
25. 5.4 Navigation
The function of navigational images should be clear
and concise.
The use of arrows and other graphical symbols in
lieu of text should be considered carefully so that their
meaning is clearly understood.
For example, by clicking on part of an image, you
may be taken to another screen and presented with
additional information.
