This glossary contains descriptions of significant terms that appear in this book.

affine transformation
Geometric image transformation, such as translation, scaling, or rotation.
The set of all samples of one type in an image, such as all red samples or all green samples.
box filter
A low-pass spatial filter composed of uniformly-weighted convolution coefficients.
bicubic interpolation
Two-dimensional cubic interpolation of pixel values based on the 16 pixels in a 4 x 4 pixel neighborhood. See also bilinear interpolation, nearest-neighbor interpolation.
bilinear interpolation
Two-dimensional linear interpolation of pixel values based on the four pixels in a 2 x 2 pixel neighborhood. See also bicubic interpolation, nearest-neighbor interpolation.
binary image
An image that consists of only two brightness levels: black and white.
chain code
A pixel-by-pixel direction code that defines boundaries of objects within an image. The chain code records an object boundary as a series of direction codes.
To assemble multiple tile regions into a single contiguous region.
color space conversion
The conversion of a color using one space to another color space, such as RGB to CMYK.
Values of samples independent of color interpretation.
compression ratio
In image compression, the ratio of an uncompressed image data file size to its compressed counterpart.
data element
Primitive types used as units of storage of image data. Data elements are individual members of a DataBuffer array.
directed graph (digraph)
A graph with one-way edges. See also directed acyclic graph (DAG).
directed acyclic graph (DAG)
A directed graph containing no cycles. This means that if there is a route from node A to node B then there is no way back.
first-order interpolation
See bilinear interpolation.
high-pass filter
A spatial filter that accentuates an image's high-frequency detail or attenuates the low-frequency detail. Contrast with low-pass filter, median filter.
A measure of the amplitude distribution of pixels within an image.
Lempel-Ziv-Welch (LZW) compression
A lossless image coding method that scans the image for repeating patterns of blocks of pixels and codes the patterns into a code list.
low-pass filter
A spatial filter that attenuates an image's high-frequency detail or accentuates the low-frequency detail. Contrast with high-pass filter, median filter.
median filter
A non-linear spatial filter used to remove noise spikes from an image.
nearest-neighbor interpolation
Two-dimensional interpolation of pixel values in which the amplitude of the interpolated sample is the amplitude of its nearest neighbor. See also bicubic interpolation, bilinear interpolation.
perspective warp
An image distortion in which objects appear trapezoidal due to foreshortening.
projective warp
See perspective warp.
The conversion of discrete image samples to digital quantities.
Abbreviation for region of interest. An area or pixel group within an image that has been selected for processing.
run-length coding
A type of lossless image data compression that scans for sequences of pixels with the same brightness level and codes them into a reduced description.
Sobel edge detection
A spatial edge detection filter that detects edges by finding the gradient of an image.
square pixel
A pixel with equal height and width.
A point operation that maps all the pixel values of an image that fall within a given range to one of a set of per-band constants.
transform coding
A form of lossy block coding that transforms blocks of an image from the spatial domain to the frequency domain.
An image manipulation technique used in printing that uses dilation and erosion to compensation for misregistration of colors.
unsharp masking
An image enhancement technique using a high-frequency accentuating filter.
zero-order interpolation
See nearest-neighbor interpolation.