3.0-CSC441-Elements-of-Multimedia-Graphic.pdf

CSC441: Multimedia Technology & Applications 2.Elements of Multimedia Graphics Compiled by: Ts. Dr. Rashidah Mokhtar Chapter Outline • • • • • • • • • Vector Graphics & Bitmapped Graphics Combining Vectors & Bitmaps Layers File Formats Shapes, Transformation & Filters 3D Graphics Resolution, Ima...

CSC441: Multimedia Technology & Applications 2.Elements of Multimedia Graphics Compiled by: Ts. Dr. Rashidah Mokhtar Chapter Outline • • • • • • • • • Vector Graphics & Bitmapped Graphics Combining Vectors & Bitmaps Layers File Formats Shapes, Transformation & Filters 3D Graphics Resolution, Image Compression Image Manipulation, Geometrical Transformation Colour: RGB Colour, Other Colour Models, Channels & Colour Correction, Consistent Colour 2 Vector Graphics & Bitmapped Graphics 3 Bitmapped Graphics • Bitmapped graphics – image is modelled as an array of pixel values • Bitmap is derived from the words ‘bit’, which means the simplest element in which only two digits are used, and ‘map’, which is a twodimensional matrix of these bits. • A bitmap is a data matrix describing the individual dots of an image. 4 Where to use bitmap? Bitmaps are an image format suited for creation of: • Photo-realistic images. • Complex drawings. • Images that require fine detail. • Bitmapped images are known as paint graphics. • A bitmap is made up of individual dots or picture elements known as pixels or pels. • Bitmapped images can have varying bit and color depths. 5 Bitmaps Available binary Combinations for Describing a Color 6 How to create bitmap? Using Clip Art Galleries • • • A clip art gallery is an assortment of graphics, photographs, sound, and video. Clip arts are a popular alternative for users who do not want to create their own images. Clip arts are available on CD-ROMs and on the Internet. Using Bitmap Software • • The industry standard for bitmap painting and editing programs are: Adobe's Photoshop and Capturing and Editing Images • Capturing and storing images directly from the screen is another way to assemble images for multimedia. • The PRINT SCREEN button in Windows and COMMANDCONTROL-SHIFT-4 keystroke on the Macintosh copies the screen image to the clipboard. • Image editing programs enable the user to: Illustrator. • Macromedia's Fireworks. • Corel's Painter. • CorelDraw. • Enhance and make composite images. • Quark Express. • Alter and distort images. • Add and delete elements. • Morph (manipulate still images to create animated transformations). Scanning Images • Users can scan images from conventional sources and make necessary alterations and manipulations. 7 Vector Graphics • • • • Vector graphics – image is modelled as mathematical description of curves, shapes • Render by computing pixels from description A vector is a line that is described by the location of its two endpoints. Vector drawing makes use of Cartesian co-ordinates. Cartesian coordinates are numbers that describe a point in two or three-dimensional space as the intersection of X, Y, and Z axis. 8 Applications of VectorDrawn Images Vector-drawn images are used in the following areas: • Computer-aided design (CAD) programs. • Graphic artists designing for the print media. • 3-D animation programs. • Applications requiring drawing of graphic shapes. • Vector images cannot be used for photorealistic images. 9 Vector-Drawn Graphics v/s Bitmaps Example of vector file format AI (Adobe Illustrator) CDR (CorelDRAW) CMX (Corel Exchange) CGM Computer Graphics Metafile DXF AutoCAD WMF Windows Metafile • Example of bitmap file format .bmp .jpeg .tiff .gif .png .raw 10 Memory Requirements • Bitmapped – any picture of w x h pixels, using c bytes per pixel occupies whc bytes • Vector – space required depends on complexity of picture (how many shapes, segments of path, etc) • Usually vector graphics smaller than bitmapped • Vector images use less memory space and have a smaller file size as compared to bitmaps. https://as.nyu.edu/communications/aem-faq/recommended-image-size.html 11 Image Editing • Vectors – drawing programs • Select individual graphic objects (shapes, paths, &c) • Transform size, position, angle, &c • Change attributes: stroke and fill &c • Bitmaps – painting programs • Select areas of pixels • Apply effects and filters 12 Scaling • Vectors • Scaling is a simple mathematical operation on stored description (before rendering) • Curves and lines remain smooth at all sizes • Bitmaps • Interpolate pixel values • More or less sophisticated algorithm • Usually produces loss of quality, blurring, jaggedness &c 13 Combining Vectors & Bitmaps 14 Combining Vectors & Bitmaps • Rasterize vectors • Lose all their vector properties • Trace bitmaps • Difficult and can only produce an approximation (parameterized) • Import bitmaps into vector drawing programs • Treated as indivisible objects • Apply complex strokes to vectors to approximate bitmapped appearance https://www.asicentral.com/news/how-to/december-2017/combine-raster-and-vector-imagesseamlessly/ 15 Layers 16 Layers • Layers offer the ability to manage and organize complex designs easily, by separating a large design into sections of related objects. • Each layer is like a sheet of transparent paper drawn on top of the layers below it. Layers are drawn as a ‘stack’, with the layer at the bottom of the list drawn first and each following layer drawn on top of the previous one. • Layers offer the ability to create unique effects through the use of their opacity and blending mode settings. These settings determine how a layer will blend with the layers below it. https://www.graphic.com/docs/layers 17 File Formats 18 78–79 File Formats Many different graphics file formats in existence Different ways of encoding image data Different amounts/form of supplementary data (Bitmaps) Different compression methods Lossless – image can be reconstructed exactly from compressed version (no loss quality) Lossy – some information discarded, image can only be reconstructed approximately (reduce the quality) 19 Vector Formats • SVG (Scalable Vector Graphics) • W3C standard, not presently widely used • SWF (Flash) • Primarily for vector animation, but can be used for still vector graphics; de facto standard • EPS (Encapsulated PostScript) • Primarily print, use declining, superseded by PDF 20 Resolution, Image Compression 21 Device Resolution • Printers, scanners: specify as dots per unit length, often dots per inch (dpi) • Desktop printer 600dpi, typesetter 1270dpi, scanner 300–3600dpi,… • Video, monitors: specify as pixel dimensions • PAL TV 768x576px, 17" CRT monitor 1024x768px,… • dpi depends on physical size of screen 22 Image Resolution • Array of pixels has pixel dimensions, but no physical dimensions • By default, displayed size depends on resolution (dpi) of output device • physical dimension = pixel dimension/resolution • Can store image resolution (ppi) in image file to maintain image's original size • Scale by device resolution/image resolution 23 Compression • Image files may be too big for network transmission, even at low resolutions • Use more sophisticated data representation or discard information to reduce data size • Effectiveness of compression will depend on actual image data • For any compression scheme, there will always be some data for which 'compressed' version is actually bigger than the original 24 Format Color Depth Image Formats Compression Transparency Uses .JPG 24 bit (16.7 million colours) Lossy Does not support Rich color photographs • Gradients • Web images .BMP 24 bit Lossless Does not support • Native format for Windows .PNG 8 bit – 24 bit Lossless Supports • Logos • Free format • Does not support Animation .GIF 8 bit (256 colors) Lossless Supports • • • Logos Animation 25 Compression • Lossless • With lossless compression, every single bit of data that was originally in the file remains after the file is uncompressed. • All of the information is completely restored. • This is generally the technique of choice for text or spreadsheet files, where losing words or financial data could pose a problem. • The Graphics Interchange File (GIF) is an image format used on the Web that provides lossless compression. • Advantages: No loss of quality, slight decreases in image file sizes. • Disadvantages: Larger files than if you were to use lossy compression. 26 Compression • Lossy • Lossy compression reduces a file by permanently eliminating certain information, especially redundant information. • When the file is uncompressed, only a part of the original information is still there (although the user may not notice it). • Generally used for video and sound, where a certain amount of information loss will not be detected by most users. • The JPEG image file, commonly used for photographs and other complex still images on the Web, is an image that has lossy compression. • Using JPEG compression, the creator can decide how much loss to introduce and make a trade-off between file size and image quality. • Advantages: Reduce file size compare to lossless compression • Disadvantages: Loss of quality 27 Lossless vs Lossy 28 Shapes, Transformation & Filters 29 Image Manipulation • Many useful operations described by analogy with darkroom techniques for altering photos • Correct deficiencies in image • Remove 'red-eye', enhance contrast,… • Create artificial effects • Filters: stylize, distort,… • Geometrical transformations • Scale (change resolution), rotate,… https://photodoto.com/photo-manipulation-tutorials/ 30 Selection • No distinct objects (contrast vector graphics) • Selection tools define an area of pixels • Draw selection (pen tool, lasso) • Select regular shape (rectangular, elliptical, 1px marquee tools) • Select on basis of colour/edges (magic wand, magnetic lasso) • Adjustments &c restricted to selected area 31 Adjustments in Photoshop • Brightness and contrast sliders • Adjust slope and intercept of linear f • Levels dialogue • Adjust endpoints by setting white and black levels • Use image histogram to choose values visually • Curves dialogue • Interactively adjust shape of graph of f 32 3D Graphics 33 3-D Drawing and Rendering • 3-D animation tools. • Features of a 3-D application. • Panoramas. 34 3-D Animation Tools 3-D animation, drawing, and rendering tools include: • Ray Dream Designer. • Caligari True Space 2. • Specular Infini-D. • Form*Z. • NewTek's Lightwave. 35 3D file format EGG — Panda3D Engine FACT — Electric Image (.fac) FBX — Autodesk FBX (.fbx) G — BRL-CAD geometry (.g) GLM — Ghoul Mesh (.glm) LWO — Lightwave Object (.lwo) LWS — Lightwave Scene (.lws) LXO — Luxology Modo (software) file (.lxo) MA — Autodesk Maya ASCII File (.ma) MB — Autodesk Maya Binary File (.mb) MD2 — Quake 2 model format (.md2) MD3 — Quake 3 model format (.md3) MDX — Blizzard Entertainment's own model format (.mdx) MESH — New York University(.m) MESH — Meshwork Model (.mesh) MM3D — Misfit Model 3d (.mm3d) NIF — Gamebryo NetImmerse File (.nif) OBJ — OBJ (.obj) 3DMF — QuickDraw 3D Metafile (.3dmf) 3DS, MAX — 3D Studio Max Model (.max, .3ds) AC — AC3D Model (.ac) AN8 — Anim8or Model (.an8) AOI — Art of Illusion Model (.aoi) B3D — Blitz3D Model (.b3d) BLEND — Blender (.blend) C4D — Cinema 4D (.c4d) Cal3D — Cal3D (.cal3d) CFL — Compressed File Library (.cfl) COB — Caligari Object (.cob) CTM — OpenCTM (.ctm) DAE — COLLADA (.dae) DTS — Torque Game Engine (.dts) .pns .jps .mpo 36 Process to make 3-D object 1. Modelling - Placing all the elements into 3-D space. 2. Extrusion - The shape of a plane surface extends some distance. [A method of creating a 3-D object using a 2-D template; giving depth to the 2-D shape.] 3. Lathing - A profile of the shape is rotated around a defined axis. 4. Shading 5. Rendering - Use of intricate algorithms to apply user-specified effects. [The process of calculating an image from all scene information (cameras, objects, materials, lights etc.). A visual representation (photo realistic) of the model.] 37 Working in 3D • 3D applications create scenes. • Scenes consist of numerous objects, the more objects in the scene, the more complex and realistic the scene is. • Objects are created by modeling them. 38 3D Modeling • Extrusion is the process of stretching a flat, 2D shape vertically to create a 3D object in a scene. • In 3D computer graphics, a lathed object is a 3D model whose vertex geometry is produced by rotating the points of a spline or other point set around a fixed axis. The lathing may be partial; the amount of rotation is not necessarily a full 360 degrees. 39 Making models realistic • Texturing: Applying images as a skin to models to make them look real. 40 Making models realistic • Lighting: Setting the mood of the scene or to simulate the environment in a realistic manner. 41 Making models realistic • Rendering: When the computer uses intricate algorithms to apply the effects you have specified on the objects you have created. 42 Colour 43 Understanding Natural Light and Color • Light comes from an atom where an electron passes from a higher to a lower energy level. • Each atom produces uniquely specific colors. • Color is the frequency of a light wave within the narrow band of the electromagnetic spectrum, to which the human eye responds. 44 Type of color model Additive color Subtractive color Monitor-specific color Color models • In the additive color method, a color is created by combining colored light sources in three primary colors - red, green, and blue (RGB). • TV and computer monitors use this method. • Colour is created by combining colored media such as paints or ink that absorb (or subtract) some parts of the color spectrum of light and reflect the others back to the eye. • Subtractive color is the process used to create color in printing (CYMK). • Colors should be used according to the target audience's monitor specifications. • The preferred monitor resolution is 800x600 pixels. • The preferred color depth is 32 bits. Models used to specify color in computer terms are: • RGB model - A 24-bit methodology where color is specified in terms of red, green, and blue values ranging from 0 to 255. • HSB and HSL models – Color is specified as an angle from 0 to 360 degrees on a color wheel. • Other models include CMYK, CIE, YIQ, YUV, and YCC. * HSB (hue, saturation, brightness) *HSL (hue, saturation, lightness) 45 Computer Colour Models • RGB hexidecimal 46 Computer Colour Models • HSB (Hue, Saturation, Brightness) 47 Computer Colour Models • HSL (Hue, Saturation, Lightness) 48 Color Palettes • Palettes are mathematical tables that define the color of pixels displayed on the screen. • Palettes are called ‘color lookup tables’ or CLUTs on Macintosh. • The most common palettes are 1, 4, 8, 16, and 24-bit deep. Microsoft Macintosh Web Safe 49 Color Depth 50 Dithering • Dithering is a process whereby the color value of each pixel is changed to the closest matching color value in the target palette. • Scanned images • This is done using a mathematical algorithm. 51 Thank you 52