archive/graphics: Add Bézier curve plotting.

archive/graphics/bezier/bezier.go

@@ -0,0 +1,53 @@
+package bezier
+
+import (
+	"image"
+	"image/color"
+	"image/draw"
+	"math"
+)
+
+// Plot plots a Bézier curve based on the provided control points, which serve
+// as weights for the Bernstein cubic polynomial basis functions.
+func Plot(p [4]float64) image.Image {
+	const (
+		width, height = 500, 500
+		scale         = 1.0 / width
+	)
+	dst := image.NewRGBA(image.Rect(0, 0, width, height))
+	draw.Draw(dst, dst.Bounds(), image.NewUniform(color.White), image.ZP, draw.Src)
+	for x := 0; x < width; x++ {
+		u := scale * float64(x)
+		y := int((p[0]*b0(u) + p[1]*b1(u) + p[2]*b2(u) + p[3]*b3(u)) / scale)
+		dst.Set(x, y, color.Black)
+	}
+	return dst
+}
+
+// b0 represents the 0th basis function of the Bernstein cubic polynomials.
+//
+//    b0(u) = (1-u)^3
+func b0(u float64) float64 {
+	return math.Pow(1-u, 3)
+}
+
+// b1 represents the 1st basis function of the Bernstein cubic polynomials.
+//
+//    b1(u) = 3u(1-u)^2
+func b1(u float64) float64 {
+	return 3 * u * math.Pow(1-u, 2)
+}
+
+// b2 represents the 2nd basis function of the Bernstein cubic polynomials.
+//
+//    b2(u) = 3u^2(1-u)
+func b2(u float64) float64 {
+	return 3 * math.Pow(u, 2) * (1 - u)
+}
+
+// b3 represents the 3rd basis function of the Bernstein cubic polynomials.
+//
+//    b3(u) = u^3
+func b3(u float64) float64 {
+	return math.Pow(u, 3)
+}

archive/graphics/cmd/plot/plot.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/mewkiz/pkg/imgutil"
+	"github.com/mewmew/playground/archive/graphics/bezier"
+)
+
+func main() {
+	for p0 := 0.0; p0 <= 1.0; p0 += 0.1 {
+		for p1 := 0.0; p1 <= 1.0; p1 += 0.1 {
+			for p2 := 0.0; p2 <= 1.0; p2 += 0.1 {
+				for p3 := 0.0; p3 <= 1.0; p3 += 0.1 {
+					p := [4]float64{p0, p1, p2, p3}
+					img := bezier.Plot(p)
+					path := fmt.Sprintf("plot_%.1f_%.1f_%.1f_%.1f.png", p0, p1, p2, p3)
+					err := imgutil.WriteFile(path, img)
+					if err != nil {
+						log.Fatalln(err)
+					}
+				}
+			}
+		}
+	}
+}