ITGS Multimedia Multimedia Multimedia Computer graphics video audio

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ITGS Multimedia

ITGS Multimedia

Multimedia • Multimedia – Computer graphics, video, audio and interactive applications – Used extensively

Multimedia • Multimedia – Computer graphics, video, audio and interactive applications – Used extensively in entertainment, science and journalism • Bitmap graphics (raster graphics) – Images that are composed of a rectangle of small dots called pixels • Photographs are made up of pixels – Resolution • The higher the number of pixels in an image, the more detail the image can hold.

Bitmap Graphics – Image editors • Used to improve the appearance of a photo

Bitmap Graphics – Image editors • Used to improve the appearance of a photo (Adobe Photoshop) – Editing tools • Cropping - taking a subsection of a photograph and removing everything else • Scaling - increasing or reducing the size of an image • Cloning - the process of copying one part of an image into another part of an image • Selection tools - very useful for highlighting just part of an image so that alterations are applied to only that area instead of the whole image • Layers - commonly used when making composite images – They allow several images to be stacked on top of eachother • Filters - effects features • Composite image - when editing tools are used to combine tow or more images – Computer generated imagery - (CGI) - a combination of photographs and computer-generated images

Social Impacts • Social impacts – It has become harder to detect alterations as

Social Impacts • Social impacts – It has become harder to detect alterations as editing software and techniques become more sophisticated • Health and Leisure – Altering the appearance of models to make them conform to a more stereotypical image of attractiveness – This creates unhealthy eating practices and negative body images in young people • Legal impacts – 1994, O. J. Simpson case • Simpson’s defense lawyer complained that a pair of rare, expensive shoes whose prints had been found at the crime scene were photoshopped into another photo of Simpson (wearing them) • TIME magazine ran a photo of his mugshot which was digitally darkened to make him look more sinister • Political impacts – 2004 Presidential election - a magazine combined two photos

Scientific Impacts together - one of John Kerry in the 70’s and one of

Scientific Impacts together - one of John Kerry in the 70’s and one of Jane Fonda at a protest of the Vietnam War • The public believed the photo, but it was a composite • Other examples of composite photos made to make situations look more dramatic – Scientific impacts • 2005 - South Korean researcher Dr. Hwang Woo Suk resigned from his position at Seoul National University after allegations that he faked images showing research results – He digitally altered images to show 11 stem cell colonies, when there were only 3 – Spotting digital fakes • The use of copy and paste and cloning tools often leaves tell-tale patterns of repeated pixels in an image – When not clearly perceptible, they can be detected by special photographic analysis software » It scans images looking for regions of similar color and content the greater the similarity between 2 regions of an image, the greater the chance of manipulation

Image Storage » Lighting inconsistencies can also be detected • Image Storage – All

Image Storage » Lighting inconsistencies can also be detected • Image Storage – All bitmap images are stored in the computer as a rectangular grid of pixels • Resolution - refers to number of pixels in the grid – Higher resolution - more detail can be stored in the image – Manufacturers of digital cameras quote the resolution in megapixels - the total number of pixels in the image, by the millions • Anything above 8 megapixels is good – Computer screens have a lower number of pixels per inch than cameras • Bit Depth or Color Depth – The number of bits used to store each pixel in the image • The higher the bit depth, the more colors an image can contain, but the more storage space it will require

Bit depth • True color – The most common bit depth for photographs »

Bit depth • True color – The most common bit depth for photographs » 3 bytes of storage are used for each pixel » In each pixel, 1 byte = red, 1 = green, 1 = blue • Storage requirements – Width x height x bit depth = storage requirement • Compression – Most file formats use some form of compression to reduce redundant, repeated data in images and reduce the amount of storage required • Lossless Compression – Looks for repeated patterns of data and stores them in a manner which requires less space, but it still allows the original data to be exactly restored

Lossless Compression All bitmap images are composed of grids of pixels (left) Each pixel

Lossless Compression All bitmap images are composed of grids of pixels (left) Each pixel represents a binary color value for the computer to display (right)

Lossless compression The values on the left represent each pixel value On the right,

Lossless compression The values on the left represent each pixel value On the right, the data is compressed to tell the computer that there are 8 pixels with the value 0 (blue), etc.

Lossy compression • Problems with Lossless Compression – Lossless compression is less effective at

Lossy compression • Problems with Lossless Compression – Lossless compression is less effective at compressing photographs, because they have a large variety of subtle shades rather than solid blocks of color • Lossy Compression – Sacrifices image quality in return for storage space » It discards data that ‘probably’ won’t be missed by the viewer » For example, if two adjacent pixels are almost the same color in an image, lossy compression might make them exactly the same – Problem: once data has been discarded, it cannot be retrieved again, so quality loss is permanent » Repeatedly editing an image, saving in a lossy format, editing and sving again will result in a gradual loss of quality at each save – Lossy format: jpeg; Lossless = tiff

PPI and DPI • Pixels per inch - how many pixels are displayed in

PPI and DPI • Pixels per inch - how many pixels are displayed in each output, whether on screen or on paper – This determines the physical size of the output and how sharp it will be • Most computer screens are 96 PPI • Most commercial and professional printers require images that are 300 PPI • Dots per inch - printer resolution - the number of ink dots that a printer produces when creating an image – Printers only have CMYK (cyan, magenta, yellow and black) ink colors, so to produce all possibly colors, they mix inks in the same spot on the paper

Vector Graphics • Vector graphics - composed of objects rather than pixels (object-oriented graphics)

Vector Graphics • Vector graphics - composed of objects rather than pixels (object-oriented graphics) – Each object is stored as a series of mathematical equations that define its starting point, ending point, and path, along with info about color and style – All objects remain separate in the image, so they can be edited, scaled, repositioned and recolored independently at any time – Most software supports only bitmapped images, so vector editors can usually export images in bitmap formats – Advantage: because they are defined mathematically, vector images can be scaled as large as required without any loss of quality – Disadvantage: because they are so complex, vector graphics require computers with faster processors to perform the number of calculations necessary

3 D Vector Images • 3 D Vector Images - Vectors are the primary

3 D Vector Images • 3 D Vector Images - Vectors are the primary method of creating three dimensional imagery – CAD - software used by architects and engineers to create 3 D technical drawings of products in development • It can be viewed in detail before it is even created • It enables them to test physical properties such as weight, strength and material • Graphics in the Movies – CGI (computer generated imagery) is often used to create animations or special effects • Motion capture - the actor wears a special suit with markers at key points such as hands, arms, legs, head. As he/she moves, the markers can be detected by a camera connected to the computer, allowing it to know the position of the main parts of the body and build up a wireframe skeleton inside the computer

Movie graphics • Textures - it’s impossible to create the required level of detail

Movie graphics • Textures - it’s impossible to create the required level of detail purely with 3 D vectors, so the overall shape of objects is modelled using a simple 3 D shape and then a 2 D bitmap texture is applied to give a deeper and more life-like appearance • Rendering or ray tracing - after properties such as reflections and light are added, the scene can be rendered to calculate how the light in a scene behaves bouncing off objects and into the virtual camera. Producing such high quality images for film and television can take hours for a single image, even on very fast computers. – Render farms - hundreds or thousands of computers working together to improve processing speed for this type of entertainment

Common video formats AVI - Audio Video Interleave Lossy; early video format MOV Used

Common video formats AVI - Audio Video Interleave Lossy; early video format MOV Used in Apple’s quick time system MP 4 -Motion Pictures Expert Group 4 New file format; more efficient lossy compression WMV-Windows Media Microsoft proprietary; Video supported on Windows

Common audio formats AAC-Advanced Audio Coding FLAC-free lossless audio codec MP 3 -MPEG Audio

Common audio formats AAC-Advanced Audio Coding FLAC-free lossless audio codec MP 3 -MPEG Audio Layer 3 Apple i. Tunes; lossy compression, supports DRM WAV - Wave Common, supported by all audio hardware and software WMA Windows only; lossy, can be streamed Open file format, lossless Lossy format; the format that changed the music industry in the 90 s

Common image formats BMP-Bitmap image Windows Paint Only TIFF-tagged image file format GIF-Graphics Interchange

Common image formats BMP-Bitmap image Windows Paint Only TIFF-tagged image file format GIF-Graphics Interchange Format PNG- Portable Network Graphics JPEG-Joint Photographic Experts Group Lossless; used in professional printing Common on the web; supports transparency Lossless, open format, supported by most browsers Most common lossy file format; produced by all digital cameras; common on web

Common image formats PSD-Photoshop Document RAW-raw image SVG-Scalable Vector Graphics Photoshop proprietary Raw image

Common image formats PSD-Photoshop Document RAW-raw image SVG-Scalable Vector Graphics Photoshop proprietary Raw image formats produced by digital SLR cameras. They maintain more color info than JPEG files and include metadata such as shutter speed and aperture. Format for storing vector graphics; actually XML test files, meaning they can be edited in normal text editors

Digital Audio • Sounds and music projects are now produced entirely digitally – Sound

Digital Audio • Sounds and music projects are now produced entirely digitally – Sound is recorded, converted into digital data (digitized) - and loaded into audio editing software, where it can be manipulated using a wide range of effects and filters • Most audio editing software represents sounds graphically as waves, and allows sections to be selected, cut, pasted and moved freely – Sample rate or sampling frequency - determines the quality of a recorded sound • Analog data captured by a microphone must be converted into digital data for the computer to process • Sample rate determines how many times each second a digital sample of the analog data is taken – More frequent samples means the digital sound will be closer to the original » CDs are high in sampling quality = 44, 100 Hz

Bit rate – Bit rate - a value displayed in some music players; the

Bit rate – Bit rate - a value displayed in some music players; the amount of data used to represent each second of audio • Higher bit rate = larger number of digital values to choose from when taking a sample • MIDI - Musical Instrument Digital Interface -communication standard for music devices, computers, and music creation software – MIDI devices have built-in recordings of different instruments played at different notes and pitches • MIDI music files contain only the instructions for how to play the instruments, not the actual sound • Digital Video – Moderately advanced video editing software allows the editor to add several video and audio tracks to allow smooth fades between videos and to provide separate audio layers such as dialog, music and background sound • Chroma key - (green or blue screen) effects allow part of a video image to be replaced with another image or video source by removing specific colors • Morphing - a source image is slowly transformed into a second image over a series of frames

Codecs • Codecs-needed to play compressed audio or video data on a computer –

Codecs • Codecs-needed to play compressed audio or video data on a computer – (compressor decompressor) is a piece of software which tells media players how to decode the particular compression format used by that video or audio data • Streaming media - video or audio that is played while it is being downloaded from the internet – Streaming media systems download a small part of the media into a buffer, which is played while another section is downloaded and loaded into the buffer • Intellectual property – Refers to non-physical creations such as stories, music, works of art and computer software • Copyright law provides protection against use of this intellectual property by unauthorized users – Copyright is automatically obtained by the author of a work when it is created there is no registration or application process involved – Intellectual property refers to the work or idea itself, not the physical media containing it » Example: making a film adaptation of a book is a breach of copyright

Fair Use • Fair use – Some countries allow exceptions to copyright laws under

Fair Use • Fair use – Some countries allow exceptions to copyright laws under certain limited circumstances • Purpose is important – Educational fair use: can’t copy full copies of a whole book • Impact on the copyright holder: will he/she lose money? • Enforcing copyright – Watermarking - photographers and artists insert a semi-transparent image , such as a name or logo, into the piece that makes it hard to remove but still easy to view the image • Free licenses – Licensing your work freely for non-commercial use • Creative Commons - free licnesing for non-commercial purposes, requiring attribution Citing Sources of material should be cited Never assume everything on the internet is free from copyright