Images Creation of multimedia images n Images obviously

Images

Creation of multimedia images n Images obviously play a very important role in multimedia products n Images may be photograph-like bitmaps, vector-based drawings, or 3 D renderings n The type of still images created depends on the display resolution, and hardware and software capabilities. n Access to the right tools and right hardware for image development is important! n E. g. , graphic designers like to have large, highresolution monitors or multiple monitors

Types of Still Images images are generated in two ways: n Bitmaps (or raster-based). n Vector-drawn graphics. n Bitmaps ( or paint graphics) – used for photo-realistic images and detailed drawings n Vector graphics – used for lines, polygons and other mathematical objects n Saved as GIF, JPEG, PNG files

Bitmaps (or raster-based)

Bitmaps n Bitmap is derived from the words ‘bit’, which means the simplest element in which only two digits are used, and ‘map’, which is a two-dimensional matrix of these bits. n A bitmap is a data matrix describing the individual dots of an image that are the smallest elements (pixels) of resolution on a computer screen or printer.

n Example

Bitmaps n Bitmaps are an image format suited for creation of: n Photo-realistic images. n Complex drawings. n Images that require fine detail. n Bitmapped images are known as paint graphics. n Bitmapped images can have varying bit and color depths.

Bitmaps • More bits provide more color depth, hence more photo-realism; • but require more memory and processing power Available binary Combinations for Describing a Color

n Monochrome just requires one bit per pixel, representing black or white BMP – 16 KB

n 8 bits per pixel allows 256 distinct colors BMP – 119 KB

n 16 bits per pixel represents 32 K distinct colors BMP – 234 KB

n 24 bits per pixel allows millions of colors BMP – 350 KB n 32 bits per pixel – trillion of colors

n Bitmaps are best for photo-realistic images or complex drawings requiring fine detail

n Bitmaps picture and their suitability of use: n Use the native Microsoft bmp format as a raw image that will later be processed. It is a faster way to process. n Use JPEG, for photo sharing on the web because of its size and quality. n GIF is normally used for diagrams, buttons, etc. , that have a small number of colours n It is also suitable for simple animation because it supports interlaced images. n PNG is almost equal to gif except that it didn’t support the animation format.

Bitmaps can be inserted by: n Using clip art galleries. Clip Art n Using bitmap software. n Capturing and editing images. Drawn n Scanning images. Scan Capture

Vector Drawings

Vector Drawings n Vector graphics are defined using formulas n RECT 0, 0, 200, RED, BLUE

Applications of Vector-Drawn Images n Vector-drawn images - created from geometric objects such as lines, rectangles, ovals, polygons using mathematical formulas n Vector-drawn images are used in the following areas: n Computer-aided design (CAD) programs. n Graphic artists designing for the print media. n 3 -D animation programs. n Applications requiring drawing of graphic shapes.

How Vector Drawing Works n Vector drawn object are drawn to the computer screen using a fraction of the memory space required by a bitmap. n A vector is a line described by its endpoints, and sometimes direction n A rectangle might be described as: n RECT, 0, 0, 200 n Starts at 0, 0 and extends 200 pixels horizontally and 200 pixels downward from the corner ( a square) n RECT, 0, 0, 200, red, blue n This is the same square with a red border filled with blue

n Example RECT 0, 0, 200, 300, RED, BLUE says n “Draw a rectangle starting at 0, 0 (upper left corner of screen) going 200 pixels horizontally right and 300 pixels downward, with a RED boundary and filled with BLUE. ” 200 pixel 300 pixel

Vector-Drawn Images v/s Bitmaps n Vector images cannot be used for photorealistic images. n Vector files are usually smaller n Vector images require a plug-in for Web-based display. n Bitmaps are not easily scalable and resizable. n Bitmaps can be converted to vector images using auto tracing.

3 -D Drawing 3 -D objects combine various shapes

3 -D Drawing and Rendering n 3 D graphics tools, such as Macromedia Extreme 3 D, or Form-Z, typically extend vector-drawn graphics in 3 dimensions (x, y and z) X Z y

3 -D Drawing and Rendering n A 3 D scene consist of object that in turn contain many small elements, such as blocks, cylinders, spheres or cones (described in terms of vector graphics) n The more elements, the finer the object’s resolution and smoothness.

3 -D Drawing and Rendering n Objects as a whole have properties such as shape, color, texture, shading & location. n A 3 D application lets you model an object’s shape, then render it completely.

Features of a 3 -D Application 1. Modeling involves drawing a shape, such as a 2 D letter, then extruding it or lathing it into a third dimension. n extruding : extending its shape along a defined path n lathing : rotating a profile of the shape around a defined axis

Features of a 3 -D Application n Modeling also deals with lighting, setting a camera view to project shadows

Features of a 3 -D Application 2. Rendering : produces a final output of a scene and is more compute-intensive.

Color n Computerized color §Computers combine red, green, and blue (RGB) light §Bit depth determines the number of possible colors 1 -bit 2 colors 4 -bit 16 colors 8 -bit 256 colors 24 -bit 16, 777, 216 colors

Color n Computerized Color n Monitors and Color – most monitors are set to display 640 X 480 pixels and 256 colors, can be adjusted for more n Called VGA ( Video Graphics Array) n Minimum configuration for Windows and MAC n More colors requires more memory

Color Wheel

Understanding Natural Light and Color n The tools we use to describe color are different when the color is printed than from when it is projected n Additive color (projected color). n Subtractive color (printed color). n Color models.

Additive Color n Additive Color: RGB n Describes colors that emanate from glowing bodies such as lights, TV, and computer monitors n In additive color models, mixing two colors results in a brighter color n Overlapping colors from 3 projectors produces new colors: n red+ green -> yellow n green+ blue -> cyan n red + blue -> magenta n TV and computer monitors use this method.

Color Models - Additive

Subtractive Color n Subtractive Color : CMYK n Mixing two colors creates a darker one n Similar to printer’s ink n Primary colors are cyan, magenta, yellow, which are complements of red, green and blue, respectively n Subtractive color is the process used to create color in printing. n Where 3 inks overlap, there is black ( gray)

Color Models - Subtractive

Color Models n Models used to specify color in computer terms are: n RGB model - A 24 -bit methodology where color is specified in terms of red, green, and blue values ranging from 0 to 255. n HSB models – Color is specified as an angle from 0 to 360 degrees on a color wheel. n Other models include CMYK

RGB Model n Add red, green and blue to create colors, so it is an additive model. n Assigns an intensity value to each pixel ranging from 0 (black) to 255 (white) n A bright red color might have R 246, G 20, B 50

HSB Model n Based on human perception of color, describe three fundamental properties of color: n Hue n Saturation (or chroma) n Brightness - relative lightness or darkness of color, also measured as %

HSB Model n Hue - color reflected from or transmitted through an object, measured on color wheel

HSB Model n Saturation (or chroma) - strength or purity of color (% of grey in proportion to hue)

HSB Model n Brightness - relative lightness or darkness of color, also measured as % 0% Black 50% 100% white

CMYK Model n Based on light-absorbing quality of ink printed on paper n As light is absorbed, part of the spectrum is absorbed and part is reflected back to eyes n Associated with printing; called a subtractive model n Four channels: Cyan (C ), magenta (M), yellow (Y) and black (K) n In theory, pure colors should produce black, but printing inks contain impurities, so this combination produces muddy brown n K is needed to produce pure black, hence CMYK is four-color process printing

Color Palettes n Palettes are mathematical tables that define the color of pixels displayed on the screen. n Palettes are called ‘color lookup tables’ or CLUTs on Macintosh. n The most common palettes are 1, 4, 8, 16, and 24 -bit deep.

Dithering: n Dithering is a process whereby the color value of each pixel is changed to the closest matching color value in the target palette. n This is done using a mathematical algorithm.

2 – Dithering

Most Popular Image File Formats n. JPEG (Joint-Photographic Experts Group) n. GIF (Graphical Interchange Format) n. PNG (Portable Network Graphic) n. Other formats: n. BMP, PSD etc.