Representing Images
n images
are stored using a variety of formats and compression techniques
n the
simplest representation is a bitmap
n bitmaps
partition an image into a grid of picture elements, called pixels, and
then convert each pixel into a bit pattern
resolution refers to the
sharpness or clarity of an image
n bitmaps
that are divided into smaller pixels will yield higher resolution images
n the
left image is stored using 96 pixels per square inch, and the right image is
stored using 48 pixels per square inch
p the
left image appears sharp, but has twice the storage requirements
when creating a bitmap of a color image, more than one bit
is required to represent each pixel
n the
most common system is to translate each pixel into a 24 bit code, known as its RGB
value: 8 bits to represent the intensity of each red/green/blue component
common
image formats implement various compression techniques to reduce storage size
n GIF (Graphics Interchange Format)
p a lossless
format, meaning no information is lost in the compression
p commonly
used for precise pictures, such as line drawings
n JPEG (Joint Photographic Experts Group)
p a lossy
format, so the compression is not fully reversible (but more efficient)
p commonly
used for photographs
