imaqDetectRotation

Usage

int imaqDetectRotation(const Image* referenceImage, const Image* testImage, PointFloat referenceCenter, PointFloat testCenter, int radius, float precision, double* angle);

Purpose

Detects the rotational shift between two images, usually a reference image containing a part at a known orientation and another image containing the part in an unknown position. This function extracts pixel values around a circular region in the reference image and compares these values to the same region in the test image. The algorithm looks for the rotational shift between those two samples.

Image Types Supported

IMAQ_IMAGE_U8, IMAQ_IMAGE_I16, IMAQ_IMAGE_SGL

Parameters

Name	Type	Description
referenceImage	const Image*	The reference image.
testImage	const Image*	The test image.
referenceCenter	PointFloat	The center point of the circular region in the reference image.
testCenter	PointFloat	The center point of the circular region in the test image.
radius	int	The radius of the circles used to detect rotation.
precision	float	The sampling period, in degrees, of the pixel values that the function extracts from the circular region.
angle	double*	On return, the angle, in degrees, between the two images. This parameter is required and cannot be NULL.

Return Value

Type	Description
int	On success, this function returns a non-zero value. On failure, this function returns 0. To get extended error information, call imaqGetLastError().

Parameter Discussion

precision—The sampling period directly affects the speed of the function. If the sampling period is high (meaning that the number of samples along the circular region is small), the processing speed of the function increases at the cost of reduced accuracy in the computed rotational shift. In many cases, you do not need a precision higher than 5 degrees to position the regions of inspection of a part. If the sampling period is less than or equal to 0, the function returns an error.