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MGH_POLYCLIP

MGH_POLYCLIP

## Purpose

Clip an arbitrary polygon on the X-Y plane to a line parallel
to the X or Y axis using the Sutherland-Hodgman algorithm.

## Category

Graphics, Region of Interest, Geometry

## Calling Sequence

result = MGH_POLYCLIP(poly, clip, dir, neg, COUNT=count)

## Return Value

The function returns the clipped polygon as a [2,n] array. The
second dimension will equal the value of the COUNT argument, except
where COUNT is 0 in which case the return value is -1.
POSITIONAL ARGUMENTS
poly (input, floating array)
A [2,m] vector defining the polygon to be clipped.
cval (input, numeric sclar)
The value of X or Y at which clipping is to occur
dir (input, integer scalar)
Specifies whether clipping value is an X (dir = 0) or Y (dir =
1) value.
neg (input, integer scalar)
Set this argument to 1 to clip to the negtive side, 0 to clip to
the positive side.

## Keyword Parameters

COUNT (output, integer)
The number of vertices in the clipped polygon.

## Procedure

The polygon is clipped using the Sutherland-Hodgman algorithm.
This function is based on JD Smith's implementation of the
Sutherland-Hodgman algorithm in his POLYCLIP function. He can
take all of the credit and none of the blame.
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