The operation computes the angle of the intensity change direction at each pixel of the inImage. Firstly the selected inOperator is used to obtain two-dimensional gradient vector at each pixel. When this vector length exceeds inEdgeThreshold the angle of the vector is calculated, scaled and stored in outDirectionsImage pixel.

This operation always generates a single-channel image with the uint8 pixel type on the output, regardless of the input image format, with following pixel values:

• When gradient length does not exceed threshold, the value of 0 is stored in pixel.
• When gradient length exceeds threshold, its angle is scaled to range 0..255 and stored in pixel value.

When a pixel value is non-zero, one can restore the original angle with the formula:

	double angle = value * 360.0 / 255.0;   // if inAngleRange == _0_360
	double angle = value * 180.0 / 255.0;   // if inAngleRange == _0_180
	double angle = value * 90.0 / 255.0;    // if inAngleRange == _0_90

To measure the angular distance between two directions described by two non-zero pixel values, use the following formulas:

    int valueDif = abs(inValue1 - inValue2);
	double angleDif = (valueDif < 128 ? (double)valueDif : (255.0 - valueDif)) * 360.0 / 255.0;  // if inAngleRange == _0_360
	double angleDif = ((double)valueDif) * 180.0 / 255.0;                                        // if inAngleRange == _0_180
	double angleDif = ((double)valueDif) * 90.0 / 255.0;                                         // if inAngleRange == _0_90

This operation is optimized for SSE41 technology for pixels of type: UINT8.

This operation is optimized for AVX2 technology for pixels of type: UINT8.

This operation is optimized for NEON technology for pixels of type: UINT8.

This operation supports automatic parallelization for multicore and multiprocessor systems.

This filter can throw an exception to report error. Read how to deal with errors in Error Handling.

List of possible exceptions:

This filter is available on Expert Complexity Level.

• GradientImage_Mask – Computes a gradient image with a Sobel or Prewitt operator.

• GradientImage – Computes a gradient image with smoothing operator of any size. The output pixels are signed.

• GradientMagnitudeImage – Measures the strength of gradient at each pixel location.