Reference: pmRemoveSizeFromEdges
pmRemoveSizeFromEdges(pm, r, b, l, t) returns the pixmap pm with r, b, l, and t pixels removed from the right, bottom, left, and top, respectively.
pmRemoveSizeFromEdges(pm, r, b, l, t) returns the pixmap pm with r, b, l, and t pixels removed from the right, bottom, left, and top, respectively.