# Edge Point Extraction

The following parameters determine how a LineMax tool detects edge points in the input image:

Parameter | Description
--- | ---
Gradient Kernel Size in Pixels | The tool uses this value to analyze the run-time image and generate a set of gradient vectors representing edge information. Use a small value when the features of interest in your images display sharp edges, where the transition between light and dark pixels occurs over a short distance. Increase this value for smoother edges in your images.
Projection Length in Pixels | Determines the number of areas used for gradient field projection A small value allows the tool to analyze the image with finer granularity than a larger value, but might require more time for the tool to execute. A larger value can improve the execution speed of the tool but might not detect the edges you want the tool to locate. In general, use a value at least as large as your setting for Gradient Kernel Size in Pixels, but it can be set higher if the tool continues to locate the desired edge points.
Contrast Threshold | Specify the minimum contrast for an edge to be considered a candidate edge for the feature you want to locate. Increase this value to locate edges of stark contrast and ignore edges where the transition between light and dark pixels is not as prominent, or lower this value when the contrast in the edges you want to locate in your images is small. The contrast of an edge is the absolute difference in average pixel values across the edge, in the range 0 through 255. Only edges with contrast greater than the value you specify are considered by the tool. For example, setting this value to 10 rejects edge points with a contrast below 10 pixel values.
Normalized Contrast Threshold | Raise the value of this parameter to discard false edge points in bright areas of your image. Be aware that setting it to 1 discards all edge points, making the tool effectively nonfunctional.