More on bitmap, jpeg and GIF files
All images that come from a scanner or digital camera are bitmap files.
A bitmap file is one that is made up of pixels (dots) in a grid. This is where the resolution setting on your camera is important. The more dots you get on the grid the finer the picture. If you use low resolution (to save space?), if you want to enlarge it on your computer or send it to a lab for enlarging and printing, it will be a poor quality picture.
Your software, when you go to enlarge the image, uses a process called interpolation and “guesses” what the additional pixels must look like. This may not be noticeable on your computer monitor, but when you come to print up the resized graphic it almost always results in a blurry and distorted image unless you started with a high resolution image setting on your camera.
Joint Photographic Experts Group (JPEG) or JPG files are a type of compressed bitmap file. The compression technique reduces the size of an image by discarding details that are typically too insignificant for the human eye to detect. JPEG file format is good for digital photography, but doesn’t work well for saving line drawings. JPEG supports 16 million colours.
A Graphics Interchange Format (GIF) file is another type of compressed bitmap file. GIF files are saved using a different compression technique which does work well for line drawings, black and white graphics etc. The GIF format is not so good for quality photos, however, since the GIF format only supports 256 colours.
Memory: Bits and Bytes
Some simple memory data:
bit – smallest unit in a computer’s memory
byte – standard unit of memory, equivalent to 8 bits.
kilobyte (KB) – standard unit of measure for a computer’s capacity – 1000 bytes – well no, actually for reasons beyond beginners it is 1024 bytes!
An A4 page of solid, formatted in Word, Times New Roman, 12pt, comes up at about 26K although if it is only text it is only about 6KB. It is said that an average book of 500 pages with 2000 characters per page probably is about a Megabyte in text.
megabyte (MB) – 1000 kilobytes (actually 1024K) or a million bytes
gigabyte (GB) – 1000 megabytes (actually 1024MB)
terabyte (TB) – 1000 gigabytes (actually 1024GB)