National Instruments IMAQTM Manuale Utente

gradient filter

An edge detection algorithm that extracts the contours in gray-level values. 
Gradient filters include the Prewitt and Sobel filters.

gray level

The brightness of a pixel in an image.

gray-level dilation

Increases the brightness of pixels in an image that are surrounded by other 
pixels with a higher intensity.

gray-level erosion

Reduces the brightness of pixels in an image that are surrounded by other 
pixels with a lower intensity.

grayscale image

An image with monochrome information.

grayscale morphology

Functions that perform morphological operations on a gray-level image.

h

Hour.

highpass attenuation

The inverse of lowpass attenuation.

highpass filter

Emphasizes the intensity variations in an image, detects edges or object 
boundaries, and enhances fine details in an image.

highpass frequency 
filter

Removes or attenuates low frequencies present in the frequency domain of 
the image. A highpass frequency filter suppresses information related to 
slow variations of light intensities in the spatial image.

highpass truncation

The inverse of lowpass truncation.

histogram

Indicates the quantitative distribution of the pixels of an image per 
gray-level value.

histogram equalization

Transforms the gray-level values of the pixels of an image to occupy the 
entire range of the histogram, thus increasing the contrast of the image. 
The histogram range in an 8-bit image is 0 to 255.

histogram inversion

Finds the photometric negative of an image. The histogram of a reversed 
image is equal to the original histogram flipped horizontally around the 
center of the histogram.

histograph

Histogram that can be wired directly into a graph.