Adv. Straight Edge Concepts

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Adv. Straight Edge Concepts

The Adv. Straight Edge step searches for straight edges along a line of pixels in the image. You can use edge detection to identify and locate discontinuities in the pixel intensities of an image. The discontinuities are typically associated with abrupt changes in pixel intensity values that characterize the boundaries of objects in a scene.

The Adv. Straight Edge step uses a kernel operator to compute the edge strength. The kernel operator is a local approximation of a Fourier transform of the first derivative. The kernel is applied to each point in the search region where edges are to be located. For example, for a kernel size of 5, the operator is a ramp function that has 5 entries in the kernel. The entries are {–2, –1, 0, 1, 2}. The width of the kernel size is user-specified and should be based on the expected sharpness, or slope, of the edges to be located.

To reduce the affect of noise in image, the edge detection algorithm can be configured to extract image data along a search region that is wider than the pixels in the image. The thickness of the search region is specified by the search width parameter. The data in the extracted region is averaged in a direction perpendicular to the search region before the edge magnitudes and edge locations are detected. A search width greater than 1 also can be used to find a “best” or “average” edge location or a poorly formed object.

Refer to the NI Vision Concepts Manual for more information about edge detection.