Filters; Convolution Filter - National Instruments IMAQ Vision for Measurement Studio User Manual

Chapter 2 Getting Measurement-Ready Images

Filters

IMAQ Vision for LabWindows/CVI User Manual
transformations. For more information about these lookup tables, see
Chapter 5, Image Processing, in the IMAQ Vision Concepts Manual.
• —Converts the pixel values of an image by replacing
imaqLookup()
them with values from a user-defined lookup table.
•
imaqEqualize()
given grayscale range. Use IMAQ Equalize to increase the contrast in
images containing few grayscale values.
•
imaqInverse()
compute the negative of the image. For example, use
before applying an automatic threshold to your image if the
background pixels are brighter than the object pixels.
Filter your image when you need to improve the sharpness of transitions in
the image or increase the overall signal-to-noise ratio of the image. You can
choose either a lowpass or highpass filter depending on your needs.
Lowpass filters remove insignificant details by smoothing the image,
removing sharp details, and smoothing the edges between the objects
and the background. You can use
lowpass filter with
imaqConvolve()
Highpass filters emphasize details, such as edges, object boundaries, or
cracks. These details represent sharp transitions in intensity value. You can
define your own highpass filter with
imaqNthOrderFilter()
imaqEdgeFilter()
imaqEdgeFilter()
predefined edge detection kernels, such as the Sobel, Prewitt, and Roberts
kernels.

Convolution Filter

The
imaqConvolve()
lowpass and highpass filters. Each filter is defined by a kernel of
coefficients. Use
imaqGetKernel()
predefined kernels do not meet your needs, define your own custom filter
using a 2D array of floating point numbers.
—Distributes the grayscale values evenly within a
—Inverts the pixel intensities of an image to
imaqLowpass()
or
imaqNthOrderFilter()
imaqConvolve()
, or you can use a predefined highpass filter with
or
imaqCannyEdgeFilter()
function allows you to find edges in an image using
function allows you to use a predefined set of
to retrieve predefined kernels. If the
2-10
imaqInverse()
or define your own
.
or
. The
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