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SYLLABUS 

  • common image file formats vector, raster, audio 11 ATAR, 12 GEN

 

VOCABULARY

  • raster = made from a grid of pixels, squares of colour made in a grid
  • raster = 1 colour value for each pixel in the image
  • vector = made from shapes with a built in maths formula for positioning these shapes
  • pixels = (pic)ture (el)ements, smallest possible unit of image data
  • file format = a standard way that a file to be made up by a computer program
  • file format = an expected file structure made by an application so that the application can open it again eg Microsoft Word   .doc  or  docx
  • file format = how the information inside the file is organised
  • file format = examples are below... they are identified by the file extension  .pdf     or     .mp3    etc

FileTypesLotsPicsLoressource of image

DETAILS

Raster Images - BMP

  • bmp is file format by microsoft as a device independent bitmap (DIB) and usually saved as .bmp
  • have a fixed resolution
  • edited in paint programs
  • no animation
  • no transparency
  • uncompressed
  • large file size
  • resolution dependent
  • require large memory to store because it stores every pixel
  • perfect for photographs with lots of colours
  • used for print, not the web
  • measured in dots per inch, and/or pixel dimensions

Raster Images - GIF

  • is a compressed image format, uses lossless LZW compression
  • animated gifs very popular on the www, even without a plugin
  • most suitable for flat colour
  • transparency = yes
  • use 8-bit colour, maximum 256 colours
  • 1 colour can be used to designate transparency
  • Common format for text, clip art, animation, icons, logos, simple diagrams, line drawings graphics with large blocks of single colour, graphics with transparent areas

Raster Images - JPEG, JPG,

  • is a lossy compressed image format
  • 24-bit colour, 16.7 million colours
  • no transparency
  • no animation
  • adjustable compression
  • ideal for colour photos
  • Common format for photographs, emailing photos, digital cameras

Raster Images - TIF

  • no animation
  • no transparency
  • compressed (lossy and lossless) or uncompressed
  • compressed is recommended
  • 24 bit, 16 million colours
  • Common format for raw bitmap data, high resolution printing, not good for internet as too long to download - too big in file size

Raster Images - PNG

  • can use 8-bit or 24-bit colour, 16 million colours
  • lossless compression
  • no animation
  • yes transparency
  • only web image format to support alpha channels
  • higher quality substitute for GIF, more effective compression
  • not good for photos, good for web when compressed
  • common format for online viewing of images
  • some older browsers need a plugin for it to work

Vector Images

  • Based on coordinates X (horizontal) and y (vertical)
  • Made up of mathematical equations
  • created from mathematical formulas used to define lines, shapes and curves
  • can be scaled to any size
  • don’t have a background
  • resolution independent (change size and still high quality)
  • shapes can be edited by moving drawing points
  • anti-aliasing softens ‘jaggies’
  • must be rendered for display
  • rendered before filters and effects
  • require little memory to store because it stores only the maths calculation and essentials
  • perfect for logos, cartoons, clipart and illustrating with few colours
  • good for fonts and text effects
  • poor colour quality = not good for photos
  • can be downloaded quickly because small file size
  • created by vector applications like Adobe Illustrator and Corel Draw
    • .wmf (Windows Meta File, can be vector or raster)
    • .dwg (dwg from drawing, CAD packages)
    • .eps (Encapsulated PostScript, used in Adobe Illustrator)
    • .pdf (Portable Document Format, first with Adobe Reader)
    • .ai (Adobe Illustrator)
    • .svg (Scalable Vector Graphics)

Vector Image  .cgm

  • stands for Computer Graphics Metafile
  • is a standard for 2D vector graphics and raster graphics and text
  • not common on the web
  • common in some technical applications

 

Vector Image  .svg

  • stands for scalable vector graphic
  • svg is a standard that defines graphics in XML format (an XML document can be defined as a string of characters)
  • can be created and edited with text editors
  • can be scaled many times without losing quality
  • can be printed at high resolution without losing quality 

 


 

FOR YOU TO DO

 Answer the following questions

  1. What is a pixel?
  2. What is resolution
  3. Which image type is mathematically defined?
  4. What is another name for a bitmap image?
  5. Name a compressed file format?
  6. What is a limitation of gif files? 

SYLLABUS 

  • common file formats for audio 11 ATAR, 12 GEN

 

VOCABULARY

  • audio = music, speech or any other sound
  • mp3 = Moving Pictures experts group MPEG-2 Layer 3 audio (mp3)
  • wav = Waveform audio file format
  • wma = Windows media audio file
  • codec = software/program to compress and decompress data, usually audio and video
  • player = special software/program to play audio files on a computer

DETAILS

Audio file - .mp3

  • mp3 is is a type of encoding
  • mp3 the most common audio file format on the internet
  • small file size, but good quality
  • file size can be reduced 10 times, but audio still fine = 1Mb per minute
  • it removes inaudible audio

Audio file - .wav

  • microsoft audio format for uncompressed audio
  • is uncompressed audio using LPCM, or linear pulse code modulation
  • LPCM is found in making audio CDs
  • file size is about 10Mb per minute

Audio file - .wma

  • is a sound file compressed by Windows media audio codec
  • designed to send audio files over the internet
  • less support than MP3
  • could be better for Windows users

 


 

FOR YOU TO DO

  1. Answer the questions below and save with your course notes.
  2. Use a sound editor to make one audio file. Save or export to different sound file types and compare file sizes and quality.
  3. Name each export version as follows; myAudioAAC256kbs.aac,   m audioAAC192kbs.aac,     myAudioMP364kbs.mp3   modify your actual file name to the export type
  4. If you are using Garage Band ver 10, you will need to choose Export to Disk.
  5. Save all your audio files to your audio files folder :)

FOR YOU TO KNOW

  1. What is the most common audio file for internet use?
  2. What is the audio file made by Windows?
  3. Why does MP3 have such a small file size?
  4. Explain mp3 audio files.
  5. Expain wav audio files.
  6. Explain wma audio files.
 
 
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