// NewMandelbrot returns a mandelbrot-set calculator
// that shows at least the area r within wr.
//
func NewMandelbrot(r crect, wr draw.Rectangle, julia bool, jpoint complex128, iterations int) *Mandelbrot {
btall := float64(wr.Dy()) / float64(wr.Dx())
atall := (imag(r.min) - imag(r.min)) / (real(r.max) - real(r.min))
if btall > atall {
// bitmap is taller than area, so expand area vertically
excess := (real(r.max)-real(r.min))*btall - (imag(r.max) - imag(r.min))
r.min -= cmplx(0, excess/2.0)
r.max += cmplx(0, excess/2.0)
} else {
// area is taller than bitmap, so expand area horizontally
excess := (imag(r.max)-imag(r.min))/btall - (real(r.max) - real(r.min))
r.min -= cmplx(excess/2.0, 0)
r.max += cmplx(excess/2.0, 0)
}
var m Mandelbrot
m.iterations = iterations
m.palette = makePalette(range0, iterations)
m.origin = r.min
m.julia = julia
m.jpoint = jpoint
m.cr = r
m.delta = cmplx(
(real(r.max)-real(r.min))/float64(wr.Dx()),
(imag(r.max)-imag(r.min))/float64(wr.Dy()),
)
m.r = wr
return &m
}
func NewTile(r draw.Rectangle, calc Fractal, img *image.RGBA, wait bool) *Tile {
t := new(Tile)
t.r = r
t.nrows = 0
if img == nil {
img = image.NewRGBA(image.Rect(0, 0, r.Dx(), r.Dy()))
}
t.calc = calc
t.image = img
if wait {
t.calculate(nil, nil)
t.nrows = img.Height()
} else {
// choose some vaguely appropriate colour
col := calc.At(centre(r))
draw.Draw(t.image, draw.Rect(0, 0, r.Dx(), r.Dy()), image.Uniform{col}, draw.ZP)
}
return t
}