Images

• Bitmap graphic


  • Made up of individual pixels
• Pixel


  Smallest identifiable area of an image, each pixel is a single colour and is given a binary value which represents that colour
• Bits per pixel


  Determines the number of available colours for an image
• Image metadata


  • Holds data about the image such as colour depth, resolution, date created, author
• Image resolution


  Relationship between file size and image resolution
• Digital image file formats

  • 5 different file formats that can be used
• A pixel's colour can be changed by changing its binary value
• Resolution


  Concentration of pixels within a specific area, defined by image width and height in pixels
• Resolution examples


  • 72 PPI (Pixels Per Inch) = typical screen resolution
  • 300 DPI (Dots Per Inch) = print quality resolution
  • Smartphones may have very high resolutions 300+ PPI
• Each pixel is given a binary value, each value represents a different colour
• Binary values for pixels

  • 0 = Black, 1 = White
• Bits per pixel


  More bits per pixel = more colour combinations
• Bits per pixel and number of colours

  • 1 bit = 2 Colours
  • 2 bits = 4 Colours
  • 3 bits = 8 Colours
  • 4 bits = 16 Colours
• Bit depth


  Number of bits per pixel, determines the number of colours that can be represented
• Number of colours


  Affects file size
• Image size


  Affects file size
• PBM monochrome images


  • Store image dimensions, change 'colours' by changing binary values
• Converting bit pattern to 8x8 icon

  • 00000011,00000101,00001010,01010100,01101000,00110000,01011000,10000000
• Pixel colour


  Each pixel has a proportion of red, green and blue, which from a distance makes up one colour
• Colour values of individual pixels are expressed in software as denary RGB values and in hexadecimal
• Metadata


  Data about data, information other than image data that is stored with a file
• Metadata includes


  • Colour depth in bits per pixel
  • Resolution (Height and width in pixels)
  • Date created
  • Author
• A bitmap graphic is made up of pixels
• Each pixel is represented in binary
• The number of bits per pixel determines the number of available colours for an image
• Image metadata holds data about

  • Colour depth, resolution, date created, author
• The greater the resolution of the image


  The greater the file size