Image Histogram Thresholds exclude a range of pixel values from the histogram, according their grey-level value. Black Threshold The Black threshold excludes dark pixels that have a grey-level value lower than the threshold value. The excluded pixels are not used to calculate histogram results. When a threshold is used and the tool is also configured to remove a percentage of pixels at the dark tail of the histogram (see the Tail Black property), the tail-removal process begins to scan the histogram at the bin corresponding to Threshold Black, instead of starting at bin 0. White Threshold The White threshold excludes light pixels that have a grey-level value higher than the threshold value.
The excluded pixels are not used to calculate histogram results. When a threshold is used and the tool is also configured to remove a percentage of pixels at the bright tail of the histogram (see the Tail White property), the tail-removal process begins to scan the histogram at the bin corresponding to Threshold White, instead of starting at bin 255. Tails A tail specifies the amount pixels to be removed from the dark and light ends of the initial his- togram. Tail Black Tail Black specifies the amount of dark pixels to be excluded from the histogram, starting from the dark end of the histogram distribution (0).
This is expressed as a percentage of the total number of pixels in the tool region of interest before tails are removed. After its creation, the histogram is scanned, starting from bin 0. The bins at the dark end of the histogram are then cleared until the amount of pixels defined by Tail Black is reached. Tail White Tail White specifies the amount of light pixels to be excluded from the histogram, starting from the light end of the histogram distribution (255). This is expressed as a percentage of the total number of pixels in the tool's region of interest before tails are removed. After its creation, the histogram is scanned, starting from bin 255.
The bins at the bright end of the histogram are then cleared until the amount of pixels defined by Tail White is reached. Region of Interest (ROI) The region of interest is the area in which the tool carries out its process. Most tool position parameters can be set through the region of interest section of the tool interface. The ACEUser's Guide, 3.6.x, 18316-000 Rev A Page 494