Representing sound

• Colour representation in images

  • Represented by a binary code
• Bitmap images


  • Made up of lots of tiny dots, called pixels
• Images


  Stored as a series of Pixels
• Number of colours in an image

  • Related to the number of bits the code has
• Black-and-white images

  • Use two colours, need 1-bit for each pixel - e.g. 0 for white and 1 for black
• Increasing Colour Depth and Resolution

  • Increases the File Size
• 1. bit images

  • Can be made up of four colours, each pixel can be one of four binary values - 00, 01, 10, and 11
• Colour depth


  • Number of bits used for each pixel
• Formula for calculating total number of colours

  Total number of colours = 2^n (where n = number of bits per pixel, or bpp)
• Most devices use a 24-bit colour depth


  • 8 bits for the levels of red, green, and blue in each pixel, can produce more colours than the human eye can see
• Colour depth examples

  • 1-bit image: 2^1 = 2 colours
  • 4-bit image: 2^4 = 16 colours
  • 24-bit image: 2^24 = 16,777,216 colours
• Image resolution


  • Number of pixels in the image, sometimes given as width x height
• Formula for calculating file size


  File size (in bits) = image resolution x colour depth = width x height x colour depth
• Metadata in images


  • Information stored in an image file to help recreate the image on screen from the binary data in each pixel
• Metadata information

  • Image's file format, height, width, colour depth, resolution
• Using a greater image resolution or colour depth

  Results in more bits in the image, giving a higher-quality image but also increasing the file size
• Without metadata


  Devices would not be able to display the image on screen as intended
• Devices need Metadata to display images


  • Metadata includes information like the time and date the image was created or last edited