add swirl

README.md

@@ -16,6 +16,7 @@
 - Circle Loop
 - Silk Sky
 - Dot Line
+- Swirl
 
 For these kinds of art, the package provides as many as parameters to control the appearance. 
 
@@ -37,6 +38,8 @@ NewRandCicle(mc, msp int, minStep, maxStep, minr, maxr float64, isRandColor bool
 NewSilkSky(circleNum int, sunRadius float64)
 NewSilkSmoke(mc, msp int, minStep, maxStep, minRadius, maxRadius float64, isRandColor bool)
 NewSpiralSquare(squareNum int, rectSide, decay float64, randColor bool)
+NewSwirl(a, b, c, d, xaixs, yaixs float64)
+NewDotLine(n int, ras, canv float64, randColor bool)
 ```
 
 ## General Options
@@ -157,6 +160,23 @@ func main() {
 
 ![](images/julia.png)
 
+### Swirl
+
+```go
+func main() {
+	rand.Seed(time.Now().Unix())
+	c := generativeart.NewCanva(1600, 1600)
+	c.SetBackground(generativeart.Azure)
+	c.FillBackground()
+	c.SetForeground(color.RGBA{113, 3, 0, 180})
+	c.SetIterations(8000000)
+	c.Draw(generativeart.NewSwirl(0.970, -1.899, -1.381, -1.506, 2.0, 2.0))
+	c.ToPNG("swirl.png")
+}
+```
+
+![](images/swirl.png)
+
 ### Circle Line
 
 ```go
@@ -246,3 +266,4 @@ Thanks for the following sites and repos, I got lots of ideas, inspiration, code
 - https://github.com/pkd2512/inktober2017
 - http://blog.dragonlab.de/2015/03/generative-art-week-1
 - https://editor.p5js.org/kenekk1/sketches/Ly-5XYvKX
+- http://paulbourke.net/fractals/peterdejong/

dotLine.go

@@ -45,7 +45,7 @@ func (d *dotLine) Generative(c *canva) {
 				newx = oldx
 				newy = oldy
 			}
-			if newx == oldx && rand.Intn(3) > 1 {
+			if newx == oldx && rand.Intn(6) > 4 {
 				ctex.DrawEllipse(float64(oldx)*d.ras+d.canv, float64(oldy)*d.ras+d.canv, c.opts.lineWidth, c.opts.lineWidth)
 				ctex.Fill()
 				continue

example/example_dotline.go

@@ -12,7 +12,7 @@ func main() {
 	c := generativeart.NewCanva(2080, 2080)
 	c.SetBackground(color.RGBA{230, 230, 230, 255})
 	c.SetLineWidth(10)
-	c.SetIterations(4000)
+	c.SetIterations(15000)
 	c.SetColorSchema(generativeart.Plasma)
 	c.FillBackground()
 	c.Draw(generativeart.NewDotLine(100, 20, 50, false))

example/example_swirl.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"github.com/jdxyw/generativeart"
+	"image/color"
+	"math/rand"
+	"time"
+)
+
+func main() {
+	rand.Seed(time.Now().Unix())
+	c := generativeart.NewCanva(1600, 1600)
+	c.SetBackground(generativeart.Azure)
+	c.FillBackground()
+	c.SetForeground(color.RGBA{113, 3, 0, 180})
+	c.SetIterations(8000000)
+	c.Draw(generativeart.NewSwirl(0.970, -1.899, -1.381, -1.506, 2.0, 2.0))
+	c.ToPNG("swirl.png")
+}

swirl.go

@@ -0,0 +1,96 @@
+package generativeart
+
+import (
+	"github.com/fogleman/gg"
+	"math"
+)
+
+type swirl struct {
+	// These are some math parameters.
+	// http://paulbourke.net/fractals/peterdejong/
+	a, b, c, d, xaixs, yaixs float64
+}
+
+func NewSwirl(a, b, c, d, xaixs, yaixs float64) *swirl {
+	return &swirl{
+		a:     a,
+		b:     b,
+		c:     c,
+		d:     d,
+		xaixs: xaixs,
+		yaixs: yaixs,
+	}
+}
+
+// Generative draws a swirl image.
+func (s *swirl) Generative(c *canva) {
+	ctex := gg.NewContextForRGBA(c.img)
+	ctex.SetLineWidth(c.opts.lineWidth)
+	start := point{
+		x: 1.0,
+		y: 1.0,
+	}
+	cl := c.opts.foreground
+
+	for i := 0; i < c.opts.nIters; i++ {
+		next := s.swirlTransform(start)
+		x, y := ConvertCartesianToPixel(next.x, next.y, s.xaixs, s.yaixs, c.height, c.width)
+		c.img.Set(x, y, cl)
+		start = next
+	}
+
+	s.removeNoisy(c)
+}
+
+func (s *swirl) swirlTransform(p point) point {
+	return point{
+		x: math.Sin(s.a*p.y) - math.Cos(s.b*p.x),
+		y: math.Sin(s.c*p.x) - math.Cos(s.d*p.y),
+	}
+}
+
+func (s *swirl) removeNoisy(c *canva) {
+	for i := 1; i < c.width-1; i++ {
+		for j := 1; j < c.height-1; j++ {
+			if c.img.At(i, j) == c.opts.background {
+				continue
+			}
+
+			var n int
+			if c.img.At(i+1, j) == c.opts.background {
+				n += 1
+			}
+			if c.img.At(i+1, j+1) == c.opts.background {
+				n += 1
+			}
+			if c.img.At(i, j+1) == c.opts.background {
+				n += 1
+			}
+
+			if c.img.At(i-1, j) == c.opts.background {
+				n += 1
+			}
+
+			if c.img.At(i-1, j+1) == c.opts.background {
+				n += 1
+			}
+
+			if c.img.At(i-1, j-1) == c.opts.background {
+				n += 1
+			}
+
+			if c.img.At(i+1, j-1) == c.opts.background {
+				n += 1
+			}
+
+			if c.img.At(i, j-1) == c.opts.background {
+				n += 1
+			}
+
+			if n > 5 {
+				c.img.Set(i, j, c.opts.background)
+			}
+
+		}
+	}
+}