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You can build a coordinate transform using pattern matching. Use 

imaqFindTransformPattern()

 to define a coordinate system based on 

the location of a reference feature. Use this technique when the object under 
inspection does not have straight, distinct edges. Complete the following 
steps to build a coordinate reference system using pattern matching.

The object may rotate 360

° in the image using this technique if you use 

rotation-invariant pattern matching.

1.

Define a template that represents the part of the object that you want 
to use as a reference feature. Refer to the 

section of this chapter for more information about defining a template.

2.

Define a rectangular ROI in which you expect to find the template.

3.

Use the options parameter to select your options for finding the pattern 
and the results that you want to overlay onto the image. When setting 
the 

Mode

 element, select 

IMAQ_MATCH_ROTATION_INVARIANT

 when 

you expect your template to appear rotated in the inspection images. 
Otherwise, select 

IMAQ_MATCH_SHIFT_INVARIANT

. Set the options 

parameter to 

NULL

 to use the default options.

4.

Choose the mode for the function. To build a coordinate transform for 
the first time, set the mode parameter to 

IMAQ_FIND_REFERENCE

. 

To update the coordinate system in subsequent images, set the mode 
parameter to 

IMAQ_UPDATE_TRANSFORM

.