Blob Analyzer There are three types of threshold functions: hard, soft and dynamic. l Thresholds are modified in the threshold function Editor, using the mouse. l The threshold function varies depending on the selected Image Segmentation mode. Hard Threshold Functions Hard thresholds produce a blob image in which pixels have only two possible states: blob or background. l Background pixels are each attributed a value of 0 in the Blob Image. l Blob pixels are each attributed a value of 1 in the Blob Image. l Hard thresholding is sometimes referred to as binary thresholding because all pixels can be considered as having one of two states:
blob or background Hard thresholding assumes that changes in data values occur at the boundary between pixels, without allowing a variation in pixels values across blob bound- aries. Because this is rarely the case, soft thresholding is more often used for applications. Hard Thresholding Example Soft Threshold Functions Soft thresholds let you use blob detection in cases where boundaries of a blob region span a few pixels in width, with varying grey-levels between the blob and the background. A soft threshold is sloped and covers a range of pixel values that become weighted pixels once they are processed.
l Weighted pixels are used in the calculation of the blob’s center of mass in proportion to their weighted value within the soft threshold range. ACEUser's Guide, 3.6.x, 18316-000 Rev A Page 409