A value generated for a region of an image which has been compared to a baseline during
the matching phase of keypoint image comparison. When a given region of a test or
training image is deemed similar to the baseline object, a similarity index value,
between 1 and 100%, indicates the degree of similarity. During automated testing, this
value is compared to the current Min Accuracy (%) setting. If it
exceeds Min Accuracy, a positive match is deemed to exist.