IS502:Multimedia Design for Information System Digital Representation for Multimedia Presenter Name: Mahmood A.Moneim Supervised By: Prof. Hesham A.Hefny Winter 2012 This template can be used as a starter file for presenting training materials in a group setting. Sections Right-click on a slide to add sections. Sections can help to organize your slides or facilitate collaboration between multiple authors. Notes Use the Notes section for delivery notes or to provide additional details for the audience. View these notes in Presentation View during your presentation. Keep in mind the font size (important for accessibility, visibility, videotaping, and online production) Coordinated colors Pay particular attention to the graphs, charts, and text boxes. Consider that attendees will print in black and white or grayscale. Run a test print to make sure your colors work when printed in pure black and white and grayscale. Graphics, tables, and graphs Keep it simple: If possible, use consistent, non-distracting styles and colors. Label all graphs and tables.

Introduction In this lecture we look at : images, starting with 1-bit images, then 8-bit gray scale images , then 24-bit color images. Bitmap versus vector graphics. Image representation Video and animation representation Audio representation Text representation Give a brief overview of the presentation. Describe the major focus of the presentation and why it is important. Introduce each of the major topics. To provide a road map for the audience, you can repeat this Overview slide throughout the presentation, highlighting the particular topic you will discuss next. By Mahmood A. Moneim

1-bit images Images consist of pixels – picture elements in digital images. 1-bit image consist of 0 or 1 bits only and thus is the simplest type of image. Hence It refer to binary image. Also called monochrome image, since it contains no color. if an image has dimension 640X480 then it requires 38.4 Kbytes of storage. By Mahmood A. Moneim

8-bit Gray-Level Images Each pixel is represented by a single byte. The entire image can be thought of as a two-dimensional array of pixel values. We refer to such an array as a bitmap. Image resolution refers to the number of pixels in a digital image. By Mahmood A. Moneim

8-bit Gray-Level Images We can think of the 8-bit image as a set of 1-bit bitplanes, where each plane consist of a 1-bit representation of the image at higher levels . Each pixel is usually stored as a byte (0-255) So a 640X480 grayscale image requires 300KB. By Mahmood A. Moneim

24-bit Color Images In a color 24-bit image, each pixel is represented by three bytes, usually representing RGB. Each value is in the range 0-255. A 640X480 24-bit color image would require 921.6 KB of storage without any compression An Important point of note is that many 24-bit color images are actually stored as 32-bit images , with the extra byte of data for each pixel storing an α (alpha) value representing special effect information. By Mahmood A. Moneim

Image Representation Images may be modeled as bitmaps or vector graphics Bitmaps: A bitmap is an array of logical pixels (stored color values) that can be mapped directly to the physical pixels on the display By Mahmood A. Moneim

Image Representation Vector Graphics: The image is stored as a mathematical description of a collection of individual lines, curves and shapes making up the image, which requires computation to render it Rendering: Generating the pixels from the model By Mahmood A. Moneim

Image Representation Using vector graphics, the image is represented in only 284 bytes Using bitmap, if the image is of a square of width 45mm and we use 24-bit for each color at a resolution of 72 pixels/inch, we need a total of 48 kilobytes . By Mahmood A. Moneim

Image Representation Vector graphics are often smaller than bitmaps, are resolution-independent and can be scaled without loss of quality, but they are only suitable for certain sorts of synthetic image, not photographs By Mahmood A. Moneim

Image Representation When scaling up an image in vector graphics format, curves remain smooth whereas in bitmap format they become blurred Original image Original image By Mahmood A. Moneim

Video and Animation Representation Displaying moving pictures depend on the phenomenon known as persistence of vision: A lag in the eye’s response to visual stimuli resulting in “after- images” being seen briefly when the stimulus is no longer present If still images are presented to the eye at a rate above the fusion frequency (around 16 to 40 pictures/sec), we experience a continuous visual sensation Thaumatropes Video http://www.youtube.com/watch?v=vypEOfWjzv8 By Mahmood A. Moneim

Video and Animation Representation A sequence of frames has two types: Live-action: Sequences recorded from real life (video) Animation: Artificially created (drawn) sequences Video frames are stored digitally as bitmapped images which require extensive compression Example: A frame that is generated by a Digital Video camera is 720 pixels wide x 576 pixels tall (PAL) and should be displayed at a rate of 25 frames/sec With no compression, each pixel requires 24 bits for color, so each frame would be 720 x 576 x 24 ≈ 1 MB and each second of video would be 25 x 1MB = 25 MB, so a 10 minute video will take ~15 GB Because of the large size of video data, compression is always applied such as the MPEG-4 standard By Mahmood A. Moneim

Video and Animation Representation Animations may be captured from external source or created in a computer Animations can be created using vector graphics (cartoon style) which results in small files compared to video By Mahmood A. Moneim

Audio Representation Sound can be represented as a sequence of samples after digitization Audio File CD audio is sampled at 44.1 kHz , higher sampling rates are sometimes used Audio delivered over the Internet is compressed, often using the MP3 codec Digital representation of audio facilitates editing (such as slowing down the music by adding samples) By Mahmood A. Moneim

Text Representation A character set is a mapping from characters to character codes Unicode is a character set capable of representing text in all known languages A font is a set of character shapes, called glyphs, which define how a character is displayed By Mahmood A. Moneim

Text Representation Many aspects of layout must be controlled when text is displayed Images can only be displayed in one way whereas the same words can be arranged in many different ways By Mahmood A. Moneim

Microsoft Engineering Excellence Questions? By Mahmood A.Moneim Microsoft Confidential