Comp Sci 1033 Final Exam Notes.docx

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Computer Science
Computer Science 1033A/B
Paul Gillespie

2 - Multimedia Overview December-03-13 4:29 PM Judgment - have 7-15 secs to make a good first impression - 4 mins to decide whether or not to keep talking Multimedia - Communications - multimedia: text, images, animation, sound, video - communications: effectively communicate a message: clear, exact, professional, make an impression - this is delivery on the internet via website Senses with the Internet #1 Visual Appeal: images, animations, video #2 Sound: sets mood easier to learn; voice recordings, music, audio technology #3 Touch: tools to navigate and create Multimedia - everything you can hear or see - any application/technology that uses any combination of text, images, sound, animation, vido - combination of moving and still pictures, sound, music and words Multimedia Uses - to inform, to educate, to sell/run businesses, to entertain Communication - IRL speak, phone, radio, tv, internet - WWW offers - accessibility - fast - directly see people (via webcam) - cheap Internet - 78.6% of the population in NA has internet - Asia has most users History 15000 BC: cave paintings 1914: silent movies 1928: first cartoon w synchronized sound - Steamboat Willie 1930s: colour movies 1937: dual sound tracks on film 1969: Arpanet (Advance Research Projects Agency Network) - beginning of Internet - requests are broken up into smaller packets and take diff routes to get to the destination - 4 locations could share info 1971: first email sent 1977: Apple starts to dominate computer market 1981: IBM PC introduced 1991: WWW debuts b/c of Tim Berners-Lee 1992: MS Windows 3.1 1992: HTML debuts 1993: first graphical browser (Mosaic: Andressen, Brina, Clark) 1996: digital cameras 1998: Google (Page, Brin) 1999: Napster 2001: iTunes, iPod 2005: YouTube 2007: Google most visited site Text - convey info - visual impact - text attributes - font, style, kerning (squishing space pairs of letters), tracking (distance between all letters), leading (vertical space between text), size, colour, x - design/layout/placement of text Font Types - serif: tails, script, body paragraphs - sans serif: no tails, block-oriented, headings Text Size - pixel - relative to screen resolution - smallest discrete component of an img on a monitor - point - linear unit (used in Word) - print unit of measure - 72 pt = 1 inch, 1 pt = 1/72 inch Text Colour - hexadecimal code (A-F, 0-9) RRGGBB - first 2 digits: amount of red, next 2: green, next 2: blue - red: #FF0000, white: #FFFFFF, black: #000000 Text Guidelines - readability - visual appeal: complementary, colour coordination, balance, text layout, mood - if you want unusual font, create .jpg/.gif file of text and insert into webpage CRAP Contrast: 2 elements similar or dissimilar Repetition: repeat some aspect Alignment: items aligned to create strong, cohesive unit Proximity: group related items together 3 - Graphics December-03-13 5:39 PM Intro to Graphics - rely on images for information, explanations, entertainment - visual appeal: professional layout Origin - non-digital medium (paper copy of a photo) - use scanner - outside world (photography) - upload to comp - create image (clip art images/scenes) - save image to a file Binary - computers only understand/speak binary (0, 1) - convert analog (words, images, sound, movies) all to digital (binary) Digitization - process of translating a piece of info into binary bits (binary digit) - bit is fundamental unit of a comp system - high volt is a 1 (on), low volt is a 0 (off) - chip inside comp keyboard that stores the binary codes for all keys pressed - then code goes to RAM (temp mem) - then to CPU, reading and deciding if it is a character or a picture - most comps use packages called bytes (8 bits) Numbering Systems - binary, octal (0-7), decimal (0-9), hexadecimal (0-9, A-F) (2 bits) = 2 = 4 values (00, 01, 11, 10), 4 shades of grey - val4e of 0 = 0 black, value of 1 = 1 white (4 bits) = 2 = 16 shades of grey (0000 blackest) Digitizing Step 1: Sampling - how many parts do we break the image/sound/vid up into - represented by a grid of pixels - pixel: smallest image component - more samples, clearer the pic Step 2: Quantizing - how many discrete values (bits) will I use to represent each part - using binary, each pixel is given numerical value corresponding to a colour Quantizing for Text - based on 8 bits (1 byte) - ASCII code system: each letter represented by 1 byte - ex. D: 01000100, G: 01000111 Colour Models Used for Web - Additive Model (RGB) - adding light to a black background - brighter than CMYK Used for Printing - Subtractive Model (CMYK) - uses printing ink, subtracts from a white background - use RGB for web because monitors display colour with RGB light How are Colours Coded? - "true colour" uses 24 bit colour representation - when assigning colour to a pixel, it can be expressed in RGB code or hexadecimal code RGB Notation - each pixel is represented by 3 values ex. light yellow = <255,255,127> - each value ranges from 0-255 - 0 means no amount - 255 means max amount - 2 bits: 256 colour shades ex. <255,0,0> is red, <0,255,0> is green - need 3 bytes for true colour: 1 byte for red, 1 byte for green, 1 byte for blue Hexadecimal Notation - #RRGGBB ex. #FF0000 = red, #000000 = black - FF means 255, 0 means 0 No, but still purple, diff shade - storing more than 10 mil colours with the human eye is useless since we can't detect more than that - so that's why we usually only use 24 bit colour Types of Graphics - bitmap - raster - made up of pixels - editing pixels: changing colour, shade, and brightness - bitmapped images come from scanner, digital cameras - image is made larger by resizing (resampling), not zooming - comp adds new pixels, guesses colours of pixels (interpolation) - squares become larger, edge more jagged - quality decreases, file size increases - small images load faster - vector - represented with lines and arcs with a mathematical relationship - describes drawing of the shape - line, rectangle, circle - size does not matter - when resized, edges clean, no distortion, quality maintained, file size increases - smaller file recording a mathematical relationship - less info needed for vectors - draw program, not natural looking photo Why need diff graphics software? - vector-based - suitable for drawings that will be sized often - .svg format to dl faster - .eps, .cdr, .dwg - Adobe Illustrator, CorelDraw, Macromedia Freehand - bitmapped-based - need Paint program (PS, etc) - .jpg, .gif, .png, .tiff, .bmp - Photoshop, Corel Photo-Paint, Jasc Paint Shop Pro Image Quality - image resolution - # of pixels per sq inch - for web: 72 ppi - for printing: 300 ppi or more (bigger file size) - incr res (ppi), incr quality, incr file size - image bit depth - (color depth) - # of bits used to represent a colour of a pixel - translates to CONTROL - more bits, more colour info, more quality, more file size 4 - More Graphics December-06-13 2:45 AM How are Images Used? For printing 1. Quality 2. File size (does not matter) For webpage 1. File size (download speed!) 2. Quality Objective on the Internet - download website asap SPEED, FILE SIZE, QUALITY, optimize the image Image Optimization - smaller file size w/o losing quality (NOT resizing) 1. File formats: choose jpg, gif, or png GIF 8 - supports a max of 8-bit colour scheme (2 = 256 colours) - good for clipart, not photos - best for large areas of solid flat colour (shapes) - tiny file sizes compared to .jpg - allows for animation - universal format - lossless JPEG - max of 24 bits/pixel (16 mil colours) - best for blends of colour, softer shadows, subtle colour changes - not good for well-defined lines or sharp contrasts - larger file sizes, lossy - full colour scheme 1. Compression: compress image data - reduce the redundancy of the image data - compress as much as you can w/o sacrificing quality Lossless - no info lost when saved - .bmp, raw - GIFs: does not get blurry - uses LZW compression by finding repeated patterns of pixels - uses algorithm Lossy - some info lost - JPGs: degrades image quality when saved - human eye is sensitive to brightness (more so than colour) so save info about brightness, and store 2 adjacent pixels with like colours as the same - uses algorithm of "how much to discard" 1. Colour resolution: # of colours used (24 bits, 16 bits, 8 bits) - colour res = bit depth - not much diff in colour res so save time by using smaller size Optimization Techniques To reduce FILE SIZE Choose FILE FORMAT - GIF - Lossless compression - Colour Resolution - Dithering - lower dl time - applies to converting jpg --> gif - reduce to 256 colours or less - adds grainy effect - juxtaposing pixels of 2 colours to create illusion of 3rd colour - browser safe palette: 216 honoured colours - if not there, will dither - Interlacing - how imgs are dl'd to your screen - image is drawn in a series of passes rather than all at the same time - Transparency - allows bg to display through image, no border - ONLY GIF AND PNG - JPG - Lossy compression - Image quality - Progressive jpeg PNG Files - created b/c of licensing issues w/ GIFs' compression scheme - lossless compression PNG-8 - 256 colours - 1 transparent colour - storing of colours more efficient in PNGs than GIFs, so PNG-8 might be smaller PNG-24 - 24 bit colour (16 mil colours) - allows for transparency on each pixel, w diff levels of opacity Image Optimization Capturing Digital Images Scanning - scanner or camera determines how many samples to take - measured in dpi (you determine) - higher samples, higher resolution - 8 in by 10 in image with 100 dpi # of samples = (8*100)*(10*100) = 800,000 - 8 in by 10 in with 300 dpi # of samples = 8*10*300*300 = 7,200,000 If printing scanned image (ex. 3600 x 2400 pixels), = pixel dimensions / print resolution (ppi) of 600 ppi 3600 pixels/600ppi = 6 inches 2400 pixels/600 ppi = 4 inches By Camera - megapixels: (1 mil of pixels) how many mils of pixels you can capture in a photograph Print size (in) = pixel dimensions / print res = 2048/300 dpi by 1536/300 dpi = 6.8" by 5.1" Displaying Images on Screen - common screen resolutions - 640 x 480 - 800 x 600 - 1024 x 768 - 1280 x 1024 - 1600 x 1200 (imageX / resX) * (imageY / resY) = take up ___ of the screen Ex. If image is 300 pixels by 200 pixels And res is 640 by 480 300/640 = 0.4688 and 200/480 = 0.4167 so 0.5*0.5 = 0.25 Review What dpi should you set for an img you want to print? - 300, since you can get 4x6 which is prevalent If you have an image that is 400x600 and printer res is 200dpi, what size will it print at? - 400/200 x 600/200 = 2 inches x 3 inches If you want to print an img at 5" x 7", what is min. size it must be in pixels for it not to look pixelated? - use 300 dpi - 5*300 = 1500 x 7*300 = 2100 Assume an image of 400x300 w res of 800x600. - (400/800) = 1/2 * (300/600) = 1/2 - thus 1/4 of screen Which of the following images will print the largest? (a) 300 pixels by 300 pixels at 100dpi (b) 300 pixels by 300 pixels at 50dpi (c) 300 pixels by 300 pixels at 10dpi - 300/10 and 300/10 = 30x30 Which of the following images will have the largest size (in kilobytes)? (a) 300 pixels by 300 pixels at 100dpi (b) 300 pixels by 300 pixels at 50dpi (c) 300 pixels by 300 pixels at 10dpi (d) They will all be the same size - not printing Assuming 24 bit depth, 300*300*24bits = 300*300*3bytes = 270 000 bytes Which is equal to 270 000 bytes / 1024 bytes = 263 kb How many MP is an image of 2000x3000? - Image size = 2000*3000 = 6000000 = 6MB 5 - The Internet December-09-13 5:01 PM Internet Fundamentals - network: group of millions of comps around world that are connected to one another - connected with wires, wirelessly, satellites The Internet - global system of interconnected comp networks that use standardized Internet Protocol Suite (TCP/IP) - Transmission Control Protocol - rules for format/transmission of data - funded by ARPA - network of networks - Internet is hardware - WWW is software that runs on the internet How to connect? - internet service provider (ISP) by modem - internet ready cable - digital subscriber line (DSL) How does the Internet work? Circuit Switching - give whole manuscript to one person, and tell you to drive on Western Rd to 401 to Yonge/Bloor and stop all traffic on the roads while doing this - how a phone line works Packet Switching - each page in the manuscript is similar to a packet and they take diff paths to get to destination - on Internet: data is sent by transferring packets (small group of bytes) - packets have a header (64 bytes) that tells destination and source, and body (512 bytes) that has the message TCP Sending end: - take large chunk of data and break into small packets - IP is responsible for sending these packets out onto Internet Receiving end: - detects lost packets, requests source to resend - rearranges and reassembles packets back into content IP - like a GPS - picks a route for a packet, stopping at routers (central switching device) which pick the next best network to send packet to - if comm. line is down, sends packet back to TCP and TCP tries sending in diff route - each comp has own unique IP address IP Address - identifies each comp/device connected to Internet - 4 #s, ranging from 0-255 - expressed in dotted quad: (but could also be in binary, decimal, hexadecimal) Summary 1. TCP breaks webpage into packets of bytes 2. TCP figures out IP address of where it wants to send the packets (destination) 3. TCP figures out IP address of where the packet is coming from (source) 1. IP picks a route for a packet, stopping at routers (devices) which pick the next best machine/network to send the packet to 1. TCP sends off each packet to first machine (IP Address) on the route (DOES NOT PREPLAN ROUTE!) 2. Packet stops at first machine, likely a router, then the router sends it to the next machine on the journey (IP Address) and so on until it gets to the final IP Address (destination) 1. Called Packet Switching IP Addresses and Domain Names - domain name: text name corresponding to an IP - a DNS (domain name system) maps the domain name to correct IP address Web Addresses and URLs - URL: uniform resource locator - Tim Berners Lee established the URL designation - subdomains used to organize web server - 4
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