Returns a pixmap with its border (outermost rectangle of pixels) extended outwards.
ExtendBorder(pm, w[, h])
pmis a pixmap
hare non-negative integers
ExtendBorder(pm, w, h) returns the pixmap obtained from
pm by extending its border (the outermost rectangle of pixels, that is, the union of the top row, bottom row, left-most column, and right-most column) outwards. The four corner pixels are made into rectangles, the remaining top and bottom pixels are copied vertically
h pixels on each side, and the remaining left and right pixels are copied horizontally
w pixels on each side.
h defaults to