Graphics Reference
In-Depth Information
Chapter 17
and Manipulation
Digital imagery appears in all forms of media today. Although most of these
images are digital photos or other types of 2D pictures that have been loaded
or scanned into a computer, an increasing number of them are generated in 3D
using sophisticated modeling and rendering software. Accompanying this trend is
a large number of image formats, most of which are interconvertible (albeit with
some loss of fidelity). Images in each format have limitations, especially in their
ability to represent wide ranges of intensity; as a result, new formats for
high
dynamic range (HDR) images
have also evolved. Because most images come
from digital cameras, it's natural to think of each pixel as storing a red, a green,
and a blue value (an
RGB
format), and then using the values to drive the red,
green, and blue colors of a screen pixel when the image is displayed. But in prac-
tice, especially with digital images, each pixel is likely to contain considerably
more information. The pixel may also contain a
depth
value representing distance
from the virtual camera, an
alpha
value representing a kind of transparency, and
even values like an identifying constant that tells what object is visible in this
pixel.
In this chapter and the one that follows, we discuss how images are typically
stored, and some techniques for manipulating them, including compositing. Then
we examine the content of images more carefully, determining how much data
an image can hold and what this says about the operations we can perform on it
reliably. Finally, with this richer view of images, we discuss different forms of
image transformation and take a look at their benefits and limitations.
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