CHAPTER 05: GRAPHICS TECHNOLOGY ~ Introduction ~ ~ Bitmap versus vector ~ ~ Colors system ~ ~ Image editing~ ~ 3-D image models ~

introduction

Graphics Technology Introduction Backbone of multimedia product. There are many sources to present graphics; picture, image, clip art, etc. Provide backgrounds, informational contents, and navigational controls. Graphics are created using a variety of tools such as paint/drawing software, scanners, and digital cameras. Graphics are stored in files in variety types of formats, depending on the size and quality.

Graphics Technology Elements of graphics Pictures versus images ??? Both are two levels of graphics abstraction. Pictures are found in the world external to the computer while images are 2D representations of pictures found in computers. Look and feel Easy to store Two basic approaches: Raster or bitmap images & Vector or metafile images.

Raster/bitmap images

Raster / Bitmap Images The most common and comprehensive form of storage. Looks as much as possible like the real-world or original product – accurate. Created as 2D sets of points on a computer display (each point can display from two to millions of colours). Points made up of a matrix of elements called pixels. Really depends on hardware capability.

Raster / Bitmap Images Where do bitmaps come from: Make a bitmap from scratch with a paint or drawing program. Grab from an active computer screen with a screen capture program, and then paste it. Capture from a photo or artwork, using a scanner or digital camera or video capture device that digitizes the image

Raster / Bitmap Images Technically characterized by the number of bits per pixel or color depth or intensity level, which determines the number of colors it can represent the width and height of the image in pixels or spatial resolution Determine the quality and size of the images

Raster / Bitmap Images Color depth (Intensity Level) Colour depth is determined by how much data, in bits, is used to determine the number of colours. 1 bit yields 2 colours 4 bits yields 16 colours 8 bits (1 byte) yields 256 colours 16 bits (2 bytes) yields 65,536 colours 24 bits (3 bytes) yields 16,777,216 colours

Number of Intensity Levels Raster / Bitmap Images Number of Bits Number of Intensity Levels Examples 1 2 0, 1 2 4 00, 01, 10, 11 4 16 0000, 0101, 1111 8 256 00110011,01010101 16 65,536 1010101010101010

Raster / Bitmap Images Monochrome display: each pixel is most commonly set to black or white (1 bit) also called as a binary image

8 bits per pixel allows 256 distinct colors Raster / Bitmap Images 8 bits per pixel allows 256 distinct colors BMP – 119KB

Raster / Bitmap Images 16 bits per pixel represents 32K distinct colors (Most graphic chipsets now supports the full 65536 colors and the color green uses the extra one bit) BMP – 234 KB

Raster / Bitmap Images 24 bits per pixel allows millions of colors BMP – 350KB

Raster / Bitmap Images More bits provide more color depth, hence more photo-realism, but require more memory and processing power Graphics production software may capture in 24-bit color and convert to 8-bit

Raster / Bitmap Images This example zoomed in at 500% illustrates how several small pixels make up a raster image.

Raster / Bitmap Images

Raster / Bitmap Images Spatial Resolution Is a number of pixels and is related to the size of image file. Spatial resolution simply refers to the smallest discernable detail in an image Vision specialists will often talk about pixel size Graphic designers will talk about dots per inch (DPI) 5.1 Megapixels

Raster / Bitmap Images 1024 Resolution

Raster / Bitmap Images 512 Resolution

Raster / Bitmap Images 256 Resolution

Raster / Bitmap Images 128 Resolution

Raster / Bitmap Images 64 Resolution

Raster / Bitmap Images 32 Resolution From your observation, what you can conclude by the number of resolution?

Determining Size of Raster Images Size can be determined by multiplying the number of pixels (spatial resolution) in the horizontal plane (x) by the number of pixels in the vertical (y), then take this value and multiply it by the number of bytes per pixels (bit depth). image size (bytes) = x * y * (bits per pixel/8) Example: A standard computer VGA display is 640 X 480 pixels for a total of 307,200 pixels. A two-color or monochrome display image consists of 38,400 bytes.

Determining Size of Raster Images (cont) Try these: A standard computer VGA display is 640 X 480 pixels for a total of 307,200 pixels … 256-colour display images 24-bit colour The more colours used, the more bytes are required to encode the image, and the more bytes required for an image, the larger the file to store the image.

Raster Image Formats The most common file formats for graphics across most computer platform. Offer a very accurate reproduction of an image based on its colour depth and resolution. Easiest files to import and export at any platforms of computers. PNG TIFF GIF JPEG/JPG BMP, MacPaint, and XBM

Raster / Bitmap Images Advantages: Disadvantages: Realistic images (high colour depth) Easy to edit Can be compressed Disadvantages: File size is too big Take more processor times to generate the image Suffers from distortion problem (replication of pixels elements)

Vector images

Vector Images Based on drawing elements or objects such as lines, rectangle, circles, etc. Stored as commands that define the individual objects. Scaling factor approach. Advantages: Small file size (less memory and disk usage). Can be resized into larger image (no distortion problem) Consists of a set of commands that are drawn when needed. Easy to convert into bitmap format

Vector Images Disadvantages: Not realistic Too many vector graphics on screen could increase processor time consumptions (too many mathematic functions must be calculated) RECT 0,0,200,200,RED,BLUE

Vector Image Formats Are common across many operating systems and a number of vendor specific applications. Example: Windows metafile is generated by processing vector commands by graphic functions in the Windows operating system. Commands are processed as a series of records that are loaded and executed in sequence. Clip arts

Vector Image Formats Windows Metafiles

Vector Images Applications of vector drawn: i. Computer-aided design (CAD); for creating the highly complex and geometric renderings needed by architects and engineers ii. Graphics artists design; for printed media without “jaggies” iii. 3D animation program; for various changes of position, rotation, and shading of light (all must be calculated mathematically)

Vector Images

colors

Image and its colors Vital component of multimedia. Picking right colours and combination of colours for multimedia involve many tries. Eye’s receptors are sensitive to red, green, and blue. Two basic methods of making color: Additive color Subtractive color

Computerized colors Additive Colour: A colour is created by combining coloured light source in three primary colours: red, green, and blue (RGB) Used for a TV or computer monitor Electron beam Combination creates all other colours

Computerized colors Subtractive Colour: A colour is created by combining coloured media such as paint or ink that absorb some parts of the colour spectrum of light Is the process used to create colour in printing Made up of three primary colours: cyan, magenta, and yellow (sometimes black) - CMYK

Computer Color Models Red, Green, Blue (RGB) Colour System: This system divides the colour signal into three channels: red(R),green(G),and blue(B).It is based on combination of additive primaries to produce colour mixtures Using 24-bit model, each red, green, and blue are set to a value of 256 choices (0-255) Eight bits of memory is required (8+8+8 = 24) to describe about 16.7 millions of colours

Computer Color Models Red, Green, Blue (RGB) Colour System: Red only (255,0,0) Red Green only (0,255,0) Green Blue only (0,0,255) Blue Red and Green, Blue subtracted (255,255,0) Yellow Red and Blue, Green subtracted (255,0,255) Magenta Green and Blue, Red subtracted (0,255,255) Cyan Red, Green, and Blue (255,255,255) White None (0,0,0) Black

RGB Color Models (0,0,0) = Pure black (1,1,1) = Pure white Blue Magenta White Cyan Green Red Black Yellow (0,0,0) = Pure black (1,1,1) = Pure white (1,0,0) = Pure red (0,1,0) = Pure green (0,0,1) = Pure blue (1,0,1) = Magenta

Computer Color Models HSB / HSL Colour System Specifying hue or colour as an angle from 0 to 360 degrees on a colour wheel, and saturation, brightness, and lightness as percentages Saturation is the intensity of a colour At 100% saturation, a colour is pure; at 0% saturation the colour is white, black or grey Lightness or brightness is the percentage of black or white that is mixed with a colour A lightness of 100% will yield a white colour, 0% is black, and 50% is the pure colour

HSB Color Models HSB Colour System: Colour Degrees Red 0° Yellow 60 ° Green 120 ° Blue 240 ° Magenta 300 ° Saturation Lightness & Brightness Hue

Computer Color Models CMYK Colour System Is less applicable to multimedia production Used primarily in the printing purposes Yellow Green Black Red Magenta Cyan White Blue (0,0,0) = Pure white (1,1,1) = Pure black Cyan + Yellow = Green

Image and its colors Colour Palettes Computer manage colour via palettes or colour look-up tables, which are mathematical tables that define the colour of any particular pixel displayed and the total number of colours that can be displayed on a system. Colour palettes are defined by indexing values correlated to red, blue, and green colours. The value ranges from 0 to 255. Unique palette value. When an image is displayed, its palette is mapped into the system palette. Is a collection of colour values in a look-up table

Colour Palettes Colour-depth Colours Available 1-bit 2 colours (Black and white) 2-bit 4 colours 4-bit 16 colours 8-bit 256 colours (good enough for colour images) 16-bit 65,536 colours (excellent for colour images) 24-bit 16.7 millions colours (totally photo-realistic).

Colour Palettes

Computerized color Colour Dithering Is a process whereby the colour value of each pixel is changed to the closest matching colour value in the target palette, using a mathematical algorithm. Consider you have a scanned or digitised images that are captured at 24 bit, with 16 million of colour depth. If this image is subsequently displayed on a computer monitor and system that is limited to less than 16 million colour depth (say 256 colours) the image must be transformed for display in the lesser colour palette.

Computerized color Colour Dithering The image palette is mapped into the new palette dimensions with colours substituted with the closest available values. The quality of dithering is depending on the algorithm used but most systems provide close approximations of the original

Computerized color Colour Dithering 32-bit color 4-bit color dithered http://www.richleader.com/bargainbinreview_color-depth.htm

Computerized color http://giphy.com/search/flashing-colors Colour Flashing This is a phenomena when images change the basic colour palette. It always happen with animation or consecutively displayed images with different palettes in each successive image. When new images are loaded, the palette is mapped into the new set of colours and a momentary flashing can be observed that can be distracting to the viewer. process to change the closest matching color value http://giphy.com/search/flashing-colors

File format

Image/Graphic Files Format Most popular formats: JPEG (Joint-Photographic Experts Group) GIF (Graphical Interchange Format) PNG (Portable Network Graphic) Other formats: BMP, PSD, TIFF/TIF, TGA, EPS, PCX, ICO

JPEG For continuous tone images, such as full-color photographs Supports more than 16 millions of color (24-bit) Uses lossy compression (averaging may lose information)

GIF For large areas of the same color and a moderate level of detail. Supports up to 256 colors Allows transparency and interlacing Uses lossless compression

PNG lossless, portable, well-compressed storage of raster images patent-free replacement for GIF also replace many common uses of TIFF Support indexed-color, grayscale, and true color images + an optional alpha channel for transparency

Other Formats BMP – Bitmap File Format. PSD – Photoshop Document. Native bitmap file format of the Microsoft Windows environment. PSD – Photoshop Document. Native bitmap file format of the Adobe Photoshop graphical editing application. TIFF – Tagged Image File Format. Used to exchange documents between different applications and platforms.

Other Formats TGA – Targa File Format. EPS – Encapsulated PostScript An image format designed for systems using Truevision video boards supported by MS-DOS platforms. EPS – Encapsulated PostScript file format. Adobe drawing format supported by most illustration and page layout programs.

Other Formats PCX – ZSoft IBM PC Paintbrush file format. One of the oldest bitmapped formats popularized by MS-DOS paint programs that first appeared in the early 1980's. ICO – Icon file format. Created by Microsoft for icons.

Editing

Editing Digital Images Image Filtering Filtering is a process of representing the range of intensities by sampling and approximation. The results of this process are much more precise,predictable,and efficient. Involves manipulating and transforming pixel values as defined by a digital filtering function. Original image is combined with a mathematical function to produce a new filtered image. The resulting value is stored in the same pixel location for the output image.

Editing Digital Images Image Filtering Filtered image can be saved as a separate file,thus preserving the original for reuse in other applications. There are two classes of filters: Global filter and Local filter

Editing Digital Images Global Filtering Transforms each and every pixel uniformly according to its filtering function regardless of its location and surroundings in the image. Example: increasing the level of brightness / darkness

Editing Digital Images Local Filtering Transforms a pixel in relation to its surrounding neighbours in the image. Example: sharpening the edges of objects in an image. Also known as spatial filtering. Edge detection

Edge Detection

Editing Digital Images Retouching Process Modification or editing of the content of an image. 2 general categories: painting and cloning methods. Painting: draw and work on a particular image,provide a number of tools(pencil,brush,area-fill,etc). Cloning: is a method whereby a selected area of an image is duplicated and pasted as many times as we desire to any image. https://www.youtube.com/watch?v=LLaOtnKTAAM

Editing Digital Images Image Composite Combines components from two or more images into a single,seamless image. The basic idea is select the portions of any particular image and paste it together as needed. Can be a difficult and timely process.

Editing Digital Images Image Composite Image layering. An image layer is a separate image channel that ordinarily contains an object that can be manipulated separately from the background or earlier scene. Objects in the topmost layer are always visible. Layers are independent.

Editing Digital Images Digital Warping A process that uses geometric operations to transform the structure of any particular images. Both still images and non-still images can be cooperated. Selecting key points are the most crucial part. For example,to change a person's facial expression by simply selecting certain key points in the original image and warping them in the output image A warp function describes the geometric transformation that is performed on the coordinates of the pixels affected. https://www.youtube.com/watch?v=9IEhwWn6XSY

The transformations in digital warping

Image/graphic : information delivery

Graphic - Information Delivery Graphics are used to convey information in multimedia products. For example, a picture of an automobile engine is much more effective than text that merely describes it.

Graphic - Information Delivery Graphics for information delivery include: Drawn images Charts and graphs Maps Scenery People

Graphic - Information Delivery 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.

Graphic - Information Delivery

Graphic - Information Delivery

Graphic - Information Delivery

3D Graphics

Three Dimensional Graphics Can be divided into two categories: Volume-based graphics and Surface-based graphics. Volume-based graphics: Voxels have features such as colour,intensity,transparency,and opacity. Medicine,physics,chemistry,and meteorology

Three Dimensional Graphics Surface-based graphics: Create a photo realistic illusion of three dimensional objects rather than manipulating them as solids. Requires a high performance computer systems running application programs written especially for them.

Three Dimensional Graphics 3-D Modelling and Development Stages : 1. Model Description Solid modelling : Portrays objects as derived from simple 3-D solids that serve as primitives within the system. For examples, cubes, cylinders, spheres, and cones can be organized, adapted, and reshaped to model some complex object.

Three Dimensional Graphics Polygon-surface modelling : A collection of connected 2-D polygons of various shapes. Multifaceted figures.

Three Dimensional Graphics Wireframe modelling : Composed of a series of connected shapes (like polygon-surface models-that are joined to others at their vertices). It may embrace curved shapes. In most 3-D applications, you can create any 2-D shape with a drawing tool or place the outline of a letter, then extrude or lathe it into the third dimension along the z axis Lathing creates a model by rotating a two-dimensional outline around a given axis. Extrusion lifts or adds a third dimension to a two-dimensional outline.

Three Dimensional Graphics Lathe A free-form object created by extrusion and a wine flute created by lathing Extrude When you extrude a plane surface, its shape extends some distance, either perpendicular to the shape’s outline or along a defined path. When you lathe a shape, a profile of the shape is rotated around a defined axis (you can set the direction) to create the 3-D object.

Three Dimensional Graphics 2. Scene Description Once the objects for an image have been modelled,they must be arranged to form a scene. Most 3-D applications provide a library of surfaces and backgrounds. Designer may also import any other images from other graphic applications that can serve as backgrounds as well.

Three Dimensional Graphics 2.1 Shading Creating the illusion of photo realism. Lambert / Flat Shading: Is the fastest for the computer to render (simplest lighting and shading model) Often used in preview mode Lack of subtlety

Three Dimensional Graphics Gouraud Shading: Is more realistic than flat shading Concern on the lighting effects on the surrounding surfaces and calculates shading from each vertex The shading values for pixels between two vertices are interpolated to create a more diffuse or smoothly varying effect.

Three Dimensional Graphics Phong Shading: Recomputed the illumination model for each pixel Results are much more realistic,though the process is more time-consuming

Three Dimensional Graphics Ray Tracing Shading: Concern on light rays that are reflected from other objects This can be traced by determining what other surfaces they contact Striking results for scenes with mirror or glass-like surfaces Extremely time-consuming

Three Dimensional Graphics 3. Rendering When you have completed the modelling of your scene or an object in it, you then must render it for final output. Rendering is when the computer finally uses intricate algorithms to apply the effects you have specified on the objects you have created. Will blend together

Three Dimensional Graphics object background A background and object rendered into an image with shadows and lighting effects final production