RISR#1v1.01 {
; Setemkia FallingTree
; Fawn@SpiritSeeker.net (NO spam, please!)
; 13 August 2001
;
; Copyright © 2001 by Setemkia FallingTree
; This algorithm may be freely used and modified, provided Setemkia
; FallingTree is credited for origination
;
; RISR == Radial Inverted Sine Region
; Used to cut out either the inside or outside of a RISR, a star shaped
; region.  The number of spokes may be one, in which case the region is
; tear shaped.
;
transform:
  bool    in  = true
  float   rad = pi/180*@rotation
  complex z0  = (#pixel-@center)*(cos(rad)-flip(sin(rad)))
  float   rz  = cabs(z0)
  if rz > 1E-20
    float s = abs(sin(@spokes/2*atan2(z0)))
    if s > 1E-20
      float rp = @radius/sqrt(s)
      if rz > rp
        in = false
      endif
    endif
  endif
  if (!@invert && !in) || (@invert && in)
    #solid = true
  endif

default:
  title = "RISR #1 v1.00"

param spokes
  caption = "Spokes"
  hint = "Number of points (spokes) in the star. An integer >= 1."
  default = 3
  min = 1
endparam

param radius
  caption = "Radius"
  hint = "Closest approach of region curve to region center."
  default = 0.5
  min = 1E-10
endparam

param center
  caption = "Center"
  hint = "Region center."
  default = (0.0,0.0)
endparam

param rotation
  caption = "Rotation"
  hint = "Rotation of the region in degrees."
  default = 0.0
  min = -360.0
  max =  360.0
endparam

param invert
  caption = "Invert Selection"
  hint = "If checked, the RIS Region is removed, otherwise \
          only the RIS Region remains."
  default = false
endparam
}