Select this parameter to compute the area of polygons formed by the outlines of objects. The outline area is calculated by utilizing a contour integration method as oppose to pixel count. If the image is spatially calibrated, the integral value is multiplied by the scaled pixel area. In general, the outline area is less than the pixel-based Area due to the fact that the outlines are considered to be passing through the centers of the boundary pixels rather than encompassing them. For example, if the object is a 5 by 5 block of pixels, it will be considered 4 pixel width wide and 4 pixel heights tall, so its outline area will be 16 square units as opposed to 25 ones given by the pixel based Area.
If objects contain holes, the holes are disregarded and not subtracted from the outline area. In such a case the outline area could be greater than the pixel-based area.