### Presence/Absence Tool Parameters

The Presence/Absence Tool has two operation modes. One is to count gray pixels within the range defined by the threshold. Another is to count edge pixels that cross over the gradient threshold value.

##### Method

- Method: Counts pixels between a range of gray values or counts pixels along an edge transition. Count Edge Pixels counts pixels along the edges of objects. Count Gray Pixels counts pixels that fall within the specified range of gray values.

##### Threshold

This changes based on whether Count Gray Pixels or Count Edge Pixels is selected in the Function menu. Count Gray Pixels allows you to set both a Low Threshold and High Threshold within which to count. Count Edge Pixels allows you to determine the point at which a feature's edges are recognized as edges.

Case: Count Gray Pixels

- Upper/Lower Threshold: Sets the pixel value(s) to be located (0 = black, 255 = white).

The Presence/Absence Tool’s Count Gray Pixels capability displays a histogram of the gray values within its region of interest. This provides a visual aide when setting the tool’s low and high threshold values. The dual slider allows you to adjust both the upper and lower thresholds. The portion of the histogram that is within the threshold range is displayed in yellow; the portion that is below the low threshold is displayed in blue; the portion that is above the high threshold is displayed in red.

- Edge Threshold: Sets the pixel value(s) to be located (0 = black, 255 = white).

##### Tolerance

- Min/Max Count: Sets the tolerance on the minimum and maximum number of pixels allowable for the inspection to pass.