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## The !manh Command: Convert to Manhattan Polygons

Syntax: !manh min_box_size [mode]
This command applies to selected polygons. It will convert each polygon to a Manhattan approximation, meaning that all sides will be horizontal or vertical.

The first argument is the size, in microns, of the minimum box width/height used to approximate non-Manhattan parts of the polygon.

The second argument is an integer that provides a choice of algorithms. If this argument is not given, a zero value is understood. Presently, there are two Manhattanizing algorithms available, specified if mode is zero or nonzero.

When mode is zero (or not given), the operation works as follows. First, a polygon is decomposed into trapezoids, each of which is subdivided horizontally if necessary so that it can be further split vertically into rectangular and right-triangular pieces. The triangular pieces are divided, recursively, into a rectangular and two residual right-triangular pieces. All of the rectangular pieces whose height and width are min_box_size or larger are kept, and reassembled into a new Manhattan polygon.

In this mode, the rectangular elements can have arbitrary size, (though sufficiently large), and there is no restriction on coordinate locations.

When mode is nonzero, a different approach is taken. First, a polygon is decomposed into a collection of trapezoids, and each trapezoid is processed. For each trapezoid, all coordinates are moved to a "grid" of size min_box_size. If either side is non-Manhattan, Bresenham's method is used to scan the trapezoid vertically, creating a new Manhattan trapezoid for each "scan line" (grid point) where the width changes. The collection of trapezoids produced is reassembled into a new Manhattan polygon.

In this mode, all coordinates are moved to the grid, thus all the rectangular elements used to build the trapezoid have height and width an integer multiple of min_box_size.

Next: The !polyfix Command: Fix Up: Layout Editing Previous: The !split Command: Atomize   Contents   Index
Stephen R. Whiteley 2022-05-28