func plotSparks(xys plotter.XYs) (image.Image, error) {
border := 4
if optRows == 1 {
border = 1
} else if optRows == 2 {
border = 2
}
height := optCharHeight * optRows
width := (optCharWidth * 2) + (optCharWidth * len(xys))
img := image.NewRGBA(image.Rect(0, 0, width, height))
_, _, ymin, ymax := plotter.XYRange(xys)
ymin = 0
for i, xy := range xys {
//xf := (xy.X - xmin) / xmax
yf := (xy.Y - ymin) / ymax
hm := height - int(float64(height-(border*2))*yf) - border
h0 := height - border
w := ((i + 1) * optCharWidth)
for h := h0; h >= hm; h = h - 2 {
var c color.RGBA
if h == hm || h == hm+1 {
c = color.RGBA{0, 255, 0, 255}
} else if h == h0 {
c = color.RGBA{0, 128, 0, 255}
} else {
p := float64(h-hm)/float64(h0-hm)*0.5 + 0.3
g := uint8(float64(255) - (p * float64(255)))
c = color.RGBA{0, g, 0, 255}
}
for j := 0; j < (optCharWidth - 2); j++ {
img.SetRGBA(w+j, h, c)
}
}
}
return img, nil
}
func (cg *ColorGrid) DataRange() (xmin, xmax, ymin, ymax float64) {
// we use the XYRange function from the plotter package
// to compute the minimum and maximum X and Y values.
return plotter.XYRange(plotter.XYValues{cg.XYZs})
}
func (s *SparkLines) DataRange() (xmin, xmax, ymin, ymax float64) {
return plotter.XYRange(s.XYs)
}