National Instruments IMAQTM - Manual (Page 35)

Chapter 3 Making Grayscale and Color Measurements
IMAQ Vision for Visual Basic User Manual 3-6 ni.com
CWIMAQRegion contains. When you know the type of shape that the
region contains, you can set the region into a shape variable and use that
variable to manipulate the shape properties. For example, the following
code resizes a rectangle selected on the viewer:
Dim MyRectangle As CWIMAQRectangle
Set MyRectangle = CWIMAQViewer1.Regions(1)
MyRectangle.Width = 100
MyRectangle.Height = 100
You also can pass CWIMAQRegion objects to any IMAQ Vision method
that takes a shape as a parameter. However, if the CWIMAQRegion does
not contain the type of shape object that the method requires, a type
mismatch error results.
Defining Regions with Masks
You can define regions to process with image masks. An image mask is
an 8-bit image of the same size as or smaller than the image you want to
process. Pixels in the mask image determine if the corresponding pixel
in the source image needs to be processed. If a pixel in the image mask
has a value other than 0, the corresponding pixel in the source image is
processed. If a pixel in the image mask has a value of 0, the corresponding
pixel in the source image is left unchanged.
You can use a mask to define particles in a grayscale image when you need
to make intensity measurements on those particles. First, threshold the
image to make a new binary image. For more information about binary
images, refer to Chapter 4,
Performing Particle Analysis . You can input the
binary image or a labeled version of the binary image as a mask image to
the intensity measurement method. If you want to make color comparisons,
convert the binary image into a CWIMAQRegions collection using
CWIMAQVision.MaskToRegions .
Measure Grayscale Statistics
You can measure grayscale statistics in images using light meters or
quantitative analysis methods. You can obtain the center of energy for an
image with the centroid method.
Use CWMachineVision.LightMeterPoint to measure the
light intensity at a point in the image. Use
CWMachineVision.LightMeterLine to get the pixel value statistics
along a line in the image, such as mean intensity, standard deviation,