Graphics (image)

Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : Menunjukkan Penggunaan Gambar pada Aplikasi Multimedia

Outline Materi What is an Image Image Media Types Bitmap Image Vector Image 3-Dimensional Graphic Models Working With Graphics

What is an Image? An image is the graphical and visual representation of some information that can be displayed on a computer screen or printed out Images come in a variety of forms: Photographs Drawings Paintings Television and motion pictures Semantics Maps, etc. Images play an important part in multimedia Navigation User interface components Help systems Clip art

Image Media Types Images can be generally divided into two formats: Bitmapped or Raster images Draw-type or Vector graphics or Metafile images Bitmapped images are stored as an array of pixels. It represents the image as an array of dots, called pixels Vector graphics are stored as geometric shape to represent the image

Bitmaps Image A pixel is the smallest element of resolution on a computer screen (Screen Resolution) A pixel is the basic unit of a digital images. Digital image is a picture that may be stored in, displayed on, processed by a computer. As mentioned, bitmap is composed of a matrix elements called pixels Each pixel can be in a specific colour and each pixel consists of two or more colors.

Bitmaps Image The range of these colours is known as the colour depth. The color depth determined “How much data in bits used to determined the number of colors”. Colour depth is measured in bits per pixel Remember: a bit (binary digit) is either 1 or 0 and that there are eight (8) bits in a byte

Colour depth 1 bit per pixel = 2 colours (monochrome) 2 bits per pixel = 4 colours 4 bits per pixel = 16 colours 8 bits per pixel = 256 colours Generally good enough for colour images 16 bits per pixel = 65536 colours Better quality for photograph-like images, also known as high colour 24 bits per pixel = >16 million possible colours Used to recreate photo realistic images, also known as true colour

Bitmaps Image The more colours that are allowed per pixel, the greater the size of the image The number of pixels is related to the size of file that required to store an image. Remember, two factors effect the size file bitmap are: Resolution Color Depth

Bitmaps images Original image Shown magnified

Image (Bitmap) pixel

Image Total number of pixels is HxV Every pixel represented by 1 bit (bw) 1 byte (greyscale) 1 byte (256 color) 2 byte (64K color) 3 byte (16M color) Pixel H (horizontal number of pixel) V (vertical number of pixel) IWAN SONJAYA, ST.MMT,MT

Greyscale Image (1 byte per pixel) Image 500 x 400 pixel Total number of pixel is 200.000 pixel Each pixel represented by 1 byte Total image capacity 200.000 x 1 byte = 200.000 byte Pixel-2 Pixel-n = 1 byte Pixel-1

Color Image (true color, 3 byte per pixel) Image 400 x 500 pixel Total number of pixel is 200.000 pixel Each pixel represented by 3 byte Total image capacity 200.000 x 3 byte = 600.000 byte Pixel-1 Pixel-2 Pixel-n = 1 byte

Color vs Greyscale vs BW Black and White

Black and White (1 bit per pixel) 8 pixels 8 pixels = 1 byte 8 pixels Greyscale Black & White

Calculating the size of a raster image Where: Width of the images measured in pixels Height of the images measured in pixels Colour depth is the number of bits used for color measured in bits per pixel Remember: 1024 bytes = 1 kilobyte (KB) 1024 kilobytes = 1 megabyte (MB)

Example A 640 x 480 pixel image in 24-bit colour would require how much disk space?

Popular bitmap formats Microsoft bitmap (.bmp) Used in microsoft windows TIFF - Tagged Image File Format (.tif) Used for faxing images (amongst other things) JPEG - Joint Photographic Expert Group (.jpg) Useful for storing photographic images GIF - Graphics Interchange Format (.gif) Used a lot on web sites PNG - Portable Network Graphics (.png) A new format for web graphics PCD – Kodak photo CD A new format for store image in a compressed form on a CD

Advantages and Disadvantages of using bitmap images Convey detail of information quickly Real life Disadvantages Depend on a Resolution Effect to the image quality Size file is big

Software to create bitmap images Popular PC packages include: Microsoft Paint Included with microsoft windows Microsoft PhotoDraw 2000 http://www.microsoft.com/office/photodraw/ Adobe Photoshop http://www.adobe.com/products/photoshop/main.html Paint Shop Pro http://www.jasc.com/psp6.html Macromedia Fireworks http://www.macromedia.com/software/fireworks/productinfo/

Vector images Vector images are stored as the set of graphic primitives required to represent the image A graphic primitive is a simple graphic based on drawing elements or objects such as shape e.g. square, line, ellipse, arc, etc. The image consists of a set of commands (mathematical equations) that are drawn the object when needed.

Vector images Storing and representing images by mathematical equations is called vector graphics or Object Oriented graphics. Each primitive object has various attributes that go to make up the entire image e.g. x-y location, fill colour, line colour, line style, etc. Example: RECTANGLE : rectangle top, left, width, height, color is ( 0, 0, 200, 200, red) CIRCLE : circle top, left, radius, color LINE : Line x1, y1, x2, y2, color

Vector images Vector image or vector graphics can be resized without losing the integrity of the original image. Scaling a vector is a mathematical operation - only the attributes change, the image is unaffected

Primitive geometric drawing objects Basic Line Polyline Arc Bezier curve Text Font, weight Shapes Circle Ellipse Rectangle Square Pie segment Triangle Pentagon, hexagon, heptagon, octagon, etc

Scaling vector graphics Shown magnified Original image

Advantages and Disadvantages of using vector image Relatively small amount of data required to represent the image. Therefore, it does not required a lot of memory to store Easier to manipulate Disadvantages Limited level of detail than can be presented in an image

Software to create images Graphics programs are tools that allow an artist to create and edit designs used in multimedia applications. Generally, graphics programs can be categorized as: Drawing programs Creating draw type graphics Provide freehand. Example geometric shape Example : Adobe Illustrator, Corel Draw, Macromedia Freehand Paint programs Those creating bitmaps Useful in creating original art Example: Paint Shop Pro Image editing programs Making changes to existing images, such as manipulating the brightness or contrast, applying textures, patterns Examples : Adobe Photoshop, Corel PhotoPaint

Vector formats Windows metafile (.wmf) Used by Microsoft Windows SVG - Scalable Vector Graphics (.svg) A new format devised for the web CGM - Computer Graphics Metafile (.cgm) Older format commonly used for clip art Adobe PostScript (.ps) A page description language used to control printers Adobe Portable Document Format (.pdf) A page description language common on the web Drawing Exchange Format (.dfx) Store 3D image created by design program AutoCAD Encapsulated PostScript (.epf) Professional printing: Illustration program, Adobe Systems, Desktop Publishing programs

3-Dimensional Graphic models A 3D model is a variation on the vector format The location of a 3-dimensional object is specified using x, y and z co-ordinates Further primitives can be found in 3D models Cube, sphere, pyramid, etc. Camera, spotlight, texture, shading etc. X 3D model Y Z

3-Dimensional Graphic models 3D graphics offer the photorealistics effects that have you seen in TV, Computer Games Examples, Motion Picture films such as: Jurassic Park, Terminator 2, Lost World and Toy Story Examples 3D programs: Carigali Truespace 3D Studio Max Infini-D

3-Dimensional Graphic models

Hardware used to acquire images Scanners and digital imaging products Many forms of scanner Drum Flat-bed Negative / slide Hand-held Important to check the optical resolution of the scanner measured in dots per inch (DPI)

Hardware used to acquire images Digital camera Uses digital memory instead of film Images are transferred to computer via a cable Can be very high resolution Stills from a camcorder or PC “web-cam” type camera Home products tend to be low resolution

Hardware used to create / edit images Graphics tablet and pen Preferred by digital artists Pressure sensitivity Digitiser tablet Preferred by technical artists Mouse has accurate crosshair to help digitise drawings Tablet and pen Digitiser

Converting image formats TrueType / PostScript Type font Bitmapped font Render as bitmap Text Bitmapped image Vector image Contour trace Optical Character Recognition (OCR)

Working With Graphics Considerations and guidelines when we are working with graphics: Choose the graphic depend on your work Choose the correct software Use minimum color depth Delivery Systems

How graphics/images can be used effectively Different types of graphics are used in different ways: Line drawing are graphical representations of physical objects. There are 3 kinds of line drawings: Isometric - represent 3-D objects without realistic perspective Orthographic - are 2-D representations of objects Perspective - represent objects in their most realistic form

How graphics/images can be used effectively ? Graphs and Tables In just a glance, graphs can provide specific data, show general trends in data or depict the relationships between data and data trends Diagrams Help users conceptualize a process, flow or interrelationship. Examples of diagrams include: Flow charts, Schematic Drawings and Block Diagrams.

Advantages and Disadvantages of using images Convey a lot of information quickly Add visual simulation and colour Can communicate across language borders Enhance other media Disadvantages Do not provide in-depth explanations Graphics rarely suffice to convey a whole message in business, technical or safety settings Can be misinterpreted Graphics should be used carefully to make sure the message is not ambiguous or cryptic

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