adding jet as a generator
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3 changed files with 43 additions and 1 deletions
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@ -17,7 +17,7 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
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Show: true,
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StrokeWidth: chart.Disabled,
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DotWidth: 5,
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DotColorProvider: chart.Viridis,
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DotColorProvider: chart.Jet,
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},
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XValues: chart.Sequence.Random(128, 1024),
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YValues: chart.Sequence.Random(128, 1024),
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@ -57,6 +57,11 @@ func ColorFromAlphaMixedRGBA(r, g, b, a uint32) Color {
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return c
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}
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// ColorChannelFromFloat returns a normalized byte from a given float value.
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func ColorChannelFromFloat(v float64) uint8 {
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return uint8(v * 255)
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}
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// Color is our internal color type because color.Color is bullshit.
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type Color struct {
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R, G, B, A uint8
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37
jet.go
Normal file
37
jet.go
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@ -0,0 +1,37 @@
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package chart
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import "github.com/wcharczuk/go-chart/drawing"
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// Jet is a color map provider based on matlab's jet color map.
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func Jet(xr, yr Range, x, y float64) drawing.Color {
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return getJetColour(y, yr.GetMin(), yr.GetMax())
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}
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func getJetColour(v, vmin, vmax float64) drawing.Color {
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c := drawing.Color{R: 0xff, G: 0xff, B: 0xff, A: 0xff} // white
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var dv float64
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if v < vmin {
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v = vmin
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}
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if v > vmax {
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v = vmax
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}
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dv = vmax - vmin
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if v < (vmin + 0.25*dv) {
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c.R = 0
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c.G = drawing.ColorChannelFromFloat(4 * (v - vmin) / dv)
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} else if v < (vmin + 0.5*dv) {
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c.R = 0
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c.B = drawing.ColorChannelFromFloat(1 + 4*(vmin+0.25*dv-v)/dv)
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} else if v < (vmin + 0.75*dv) {
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c.R = drawing.ColorChannelFromFloat(4 * (v - vmin - 0.5*dv) / dv)
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c.B = 0
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} else {
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c.G = drawing.ColorChannelFromFloat(1 + 4*(vmin+0.75*dv-v)/dv)
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c.B = 0
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}
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return c
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}
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