Computer Science unit 2.1

• Bitmaps are constructed by pixels
• Each pixel of a bitmap is stored in binary
• The number of bits required for each pixel depends on the amount of colours
• The number of bits for each pixel is known as what?

  Colour depth
• Metadata is what?

  additional data stored within the image
• The greater the colour depth and resolution, the larger the file size of the image
• Photographs are stored in 24-bit colour depth
• Sound file size - total number of bits in a sound
• sound file size can be calculated by number of samples per second x number of bits per sample x length of sample
• bit depth - the number of bits stored per sample
• the higher number of bits or sampler per second, the greater the quality and bigger the file size
• sample rate - number of samples per second
• compression reduces the number of bits in a file making the capacity higher and data transfer quicker
• lossy compression - greatly reduces the file size and some data is lost reduces the quality
• lossy compression is suitable for images sound and video cannot be used on text and executable files
• lossless compression - data is not lost it is encoded differently and can be turned back into original format
• lossless compression can be used on all types of data it does not reduce file size and is most suitable for documents and executable files