1

Bitmap Graphics

It is represented by a dot pattern in which each dot is called a pixel.

Each pixel can be in any one of the colors available and the color of each pixel is represented by a code.

For a monochrome bitmap picture, each pixel is either black or white. One bit is enough to code the color of a pixel.

2

10 x 10 pixels

3

Bitmap Graphics ...

The resolution of the picture is determined by the size of each pixel and so the number of pixels used for representing it.

The higher the number of pixels, the sharper the picture and so the higher the resolution.

For a full screen monochrome bitmap picture, the storage space required is 640x480 or 372,000 bits.

4

Bitmap Graphics ...

To have better pictures, more than two choices of color are provided for each pixel.

Grayscale graphics are created by using shades of gray, if eight levels of grayscale are provided, 3 bits will be needed for coding each pixel (23=8).

5

Vector Graphics

It is divided into a number of objects and each object is coded by the method of drawing it.

A rectangle object

A circle object

A straight line object

6

Vector Graphics ...

The method of drawing an object is represented by a mathematical formula that specifies the attributes of that object.

The attributes include the shape, the size, the line width, the line color, the fill color, and so on.

Through the formulas, the objects can be re-constructed.

7

Vector Graphics ... The storage space required for a vector

graphics picture does not depend on the size of the picture but on its complexity.

A vector graphics picture usually requires much less storage space than a bitmap picture.

Storing the formulas for constructing a picture is likely to take less storage space than storing the state of the individual dots of the picture.

8

Vector Graphics ...

Circle(15,27,18,red,1.15,light yellow,…)

shape

radius

center

Line color

Line thickness

Fill color

Microsoft Clipart

Bitmap or vector ??

10

Two Main Advantages

A vector graphics picture requires much less storage space than a bitmap picture.– Storing the formulas for constructing a

picture is likely to take less storage space than storing the state of the individual dots of the picture.

11

Two Main Advantages …

Vector graphics can be re-sized or re-scaled without distortion.– Re-sizing or re-scaling an object oriented

object is just changing the corresponding attributes in its formula.

Enlarging a bitmap picture causes a chunky effect.

Saw-tooth results on curve.

12

Major Disadvantage

The picture created cannot look like as realistic as bitmap pictures.

13

Creating Graphics

There are many different kinds of graphics software in the market.

Some of the more important ones are drawing software, painting software, presentation software, charting software, and CAD (or Computer Aided Design) software.

14

Painting Software

A painting program creates an image by setting the colors of individual screen pixels.

The pictures created by a painting program are thus bitmap graphics.

The Paint supplied by Microsoft Windows.

15

Drawing Software

A drawing program generates formulas to represent the objects drawn by users.

The pictures created are thus object-oriented graphics.

With them, you can easily draw lines, either straight or curved, and shapes, like circle, rectangle, or triangle.

16

The objects created in a drawing program can be moved freely around.

Grouping or overlaying simpler objects can form more complicated objects, which can in turn be used to create complex drawings.

PowerPoint and Coral Draw are currently the two most popular drawing programs.

17

Presentation Software

A presentation program is a program that helps users to prepare the essential components of a presentation – presentation outlines, slide show, audience handouts, and speaker’s notes. Users can also use a presentation program to run an on-screen slide show.

18

Charting Software

A charting program helps users to prepare graphs and charts. Graphs and chart of different types can help users to see the trends of data.

Commonly used graphs include line graphs, bar graphs, stacked bar graphs and pie charts.

19

CAD Software

CAD (Computer Aided Design) involves the use of computer to aid the design process. CAD software is a type of program allowing users to perform design work on screen.

CAD programs enable designers to create three-dimensional objects on screen that can be resized, rotated, flipped, examined internally or externally, and many more.

20

Engineering and technical drawings can be created in a much more efficient way.

21

Importing Graphics

Three common ways are importing from– Clip art libraries– Using image scanners, and– Capturing the screen.

22

Clip Art Library

A clip art picture is a computer image that can be incorporated into computer documents.

The creation of clip art pictures in difficult to many computer users. Fortunately, there are many ready-made clip art pictures selling in the market and a collection of clip art pictures is called a clip art library.

23

Image Scanner

An image scanner is a direct-entry device used to capture an existing two-dimensional image on paper, which may be a photograph or a drawing, into a computer system.

It converts an image on paper into a digital form that us usable by computers.

Hand-held scanner, flatbed scanner.

24

Screen Capture

To copy the contents of the entire screen onto the clipboard, press the <Print Screen> button.

Although the above way of capturing the screen is easy and convenient, the screen capture is not of very high quality.

25

Bitmap An image or other collection of data

represented as an array of bits. In bitmap graphics, an image is displayed on the screen as a collection of tiny squares called pixels, which together form a pattern. Each pixel in the image corresponds with one or more bits; the number of bits per pixel determines how many shades of gray or colors can be displayed.

Typically 8-bit file.

26

JPEG

Joint Photographic Experts Group. A format for storing high-quality color and grayscale photographs in bitmap form; also the group that developed the format.

JPEG provides lossy compression by segmenting the picture into small blocks which are divided to get the desired ratio; the process is reversed to decompress the image.

27

JPEG …

Maximum color depth is 24 bits. Used for scanned photographs, artwork,

and other images that include smooth color variations.

28

GIF

Graphics Interchange Format. A format used for displaying bitmap images on World Wide Web pages, usually called a "gif" because .gif is the filename extension.These files use lossless compression and can have 256 colors.

29

GIF …

Maximum color depth is 8 bits. The standard format to be used in

Internet. For line drawings, single-color borders,

and simple cartoons.