National Instruments IMAQTM 用户手册

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optical representation

Contains the low-frequency information at the center and the high- 
frequency information at the corners of an FFT-transformed image.

outer gradient

Finds the outer boundary of objects.

palette

The gradation of colors used to display an image on screen, usually defined 
by a CLUT.

particle

A connected region or grouping of non-zero pixels in a binary image.

particle analysis

A series of processing operations and analysis functions that produce some 
information about the particles in an image.

pattern matching

The technique used to locate quickly a grayscale template within a 
grayscale image

picture element

An element of a digital image. Also called pixel.

pixel

Picture element. The smallest division that makes up the video scan line. 
For display on a computer monitor, a pixel's optimum dimension is square 
(aspect ratio of 1:1, or the width equal to the height).

pixel aspect ratio

The ratio between the physical horizontal size and the vertical size of the 
region covered by the pixel. An acquired pixel should optimally be square, 
thus the optimal value is 1.0, but typically it falls between 0.95 and 1.05, 
depending on camera quality.

pixel calibration

Directly calibrates the physical dimensions of a pixel in an image.

pixel depth

The number of bits used to represent the gray level of a pixel.

PNG

Portable Network Graphic. An image file format for storing 8-bit, 16-bit, 
and color images with lossless compression. PNG images have the file 
extension PNG.

Prewitt filter

An edge detection algorithm that extracts the contours in gray-level values 
using a 3

× 3 filter kernel.