refactor: change project structure and package name

pkg/chart/jet.go

@@ -0,0 +1,35 @@
+package chart
+
+import (
+	"github.com/d-Rickyy-b/go-chart-x/v2/pkg/drawing"
+)
+
+// Jet is a color map provider based on matlab's jet color map.
+func Jet(v, vmin, vmax float64) drawing.Color {
+	c := drawing.Color{R: 0xff, G: 0xff, B: 0xff, A: 0xff} // white
+	var dv float64
+
+	if v < vmin {
+		v = vmin
+	}
+	if v > vmax {
+		v = vmax
+	}
+	dv = vmax - vmin
+
+	if v < (vmin + 0.25*dv) {
+		c.R = 0
+		c.G = drawing.ColorChannelFromFloat(4 * (v - vmin) / dv)
+	} else if v < (vmin + 0.5*dv) {
+		c.R = 0
+		c.B = drawing.ColorChannelFromFloat(1 + 4*(vmin+0.25*dv-v)/dv)
+	} else if v < (vmin + 0.75*dv) {
+		c.R = drawing.ColorChannelFromFloat(4 * (v - vmin - 0.5*dv) / dv)
+		c.B = 0
+	} else {
+		c.G = drawing.ColorChannelFromFloat(1 + 4*(vmin+0.75*dv-v)/dv)
+		c.B = 0
+	}
+
+	return c
+}