Graphics Programs Reference
In-Depth Information
Continuous tone images
have to be converted to
digital form before they
can be manipulated by
computers.
Computers are amazing machines. Their strength is in being able to perform millions of
mathematical calculations per second. To apply this ability to working with images, we
must start with a description of pictures that the computer can understand.
This means that the images must be in a digital form. This is quite different from the way
our eye, or any film-based camera, sees the world. With film, for example, we record pictures
as a series of 'continuous tones' that blend seamlessly with each other. To make a version of
the image that the computer can use, these tones need to be converted to a digital form.
The process involves sampling the image at regular intervals and assigning a specific color
and brightness to each sample. In this way, a grid of colors and tones is created which, when
viewed from a distance, will appear like the original image or scene. Each individual grid
section is called a picture element, or pixel.
Digital files can be created by taking pictures with a digital camera or by using a scanner
to convert existing prints or negatives into pixel form. Most digital cameras have a grid of
sensors, called charge-coupled devices (CCDs), in the place where traditional cameras would
have film. Each sensor measures the brightness and color of the light that hits it. When the
values from all sensors are collected and collated, a digital picture results.
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