Contrast Presence/Absence Tool - Histogram Tab

The Histogram Tab is a histogram representation of the greyscale values of the pixels in the region.

• The X-axis of the graph represents the total number of greyscale values (0 to 255, or 256 total shades of grey).
• The Y-axis of the graph represents the number of pixels at a given greyscale value, and the scale is established by displaying the greyscale value with the greatest number of pixels.

• The three blue vertical lines indicate the mean greyscale value below the threshold, the threshold and the mean greyscale value above the threshold, respectively.