[wip]add domian wrap

README.md

@@ -576,3 +576,4 @@ Thanks for the following sites and repos, I got lots of ideas, inspiration, code
 - <https://openprocessing.org/sketch/1071233>
 - <https://openprocessing.org/user/139364>
 - <https://openprocessing.org/sketch/792407>
+- <https://www.iquilezles.org/www/articles/warp/warp.htm>

arts/domainwrap.go

@@ -0,0 +1,49 @@
+package arts
+
+import (
+	"github.com/fogleman/gg"
+	"github.com/jdxyw/generativeart"
+	"github.com/jdxyw/generativeart/common"
+)
+
+type domainWrap struct {
+	noise            *common.PerlinNoise
+	scale            float64
+	xOffset, yOffset float64
+}
+
+// NewDomainWrap returns a domainWrap object.
+func NewDomainWrap(scale, xOffset, yOffset float64) *domainWrap {
+	return &domainWrap{
+		scale:   scale,
+		xOffset: xOffset,
+		yOffset: yOffset,
+		noise:   common.NewPerlinNoise(),
+	}
+}
+
+// Generative draws a domain warp image.
+// Reference: https://www.iquilezles.org/www/articles/warp/warp.htm
+func (d *domainWrap) Generative(c *generativeart.Canva) {
+	_ = gg.NewContextForRGBA(c.Img())
+
+	for h := 0.0; h < float64(c.Height()); h += 1.0 {
+		for w := 0.0; h < float64(c.Width()); h += 1.0 {
+			_, _, _ = d.pattern(w*d.scale, h*d.scale, d.xOffset, d.yOffset)
+		}
+	}
+}
+
+func (d *domainWrap) pattern(x, y, xOffest, yOffset float64) (float64, float64, float64) {
+	qx := d.fbm(x+xOffest, y+yOffset)
+	qy := d.fbm(x+xOffest+5.2, y+yOffset+1.3)
+
+	rx := d.fbm(x+4.0*qx+1.7, y+4.0*qy+9.2)
+	ry := d.fbm(x+4.0*qx+8.3, y+4.0*qy+2.8)
+
+	return d.fbm(qx+4*rx, qy+4*ry), common.Magnitude(qx, qy), common.Magnitude(rx, ry)
+}
+
+func (d *domainWrap) fbm(x, y float64) float64 {
+	return d.noise.Noise2D(x, y)
+}

common/calculation.go

@@ -49,3 +49,7 @@ func LerpColor(c1, c2 color.RGBA, ratio float64) color.RGBA {
 
 	return color.RGBA{r, g, b, a}
 }
+
+func Magnitude(x, y float64) float64 {
+	return math.Sqrt(x*x + y*y)
+}