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// Planets: an exploration of scale
package main
import (
"flag"
"image/png"
"os"
"github.com/ajstarks/svgo"
)
var ssDist = []float64{
0.00, // Sun
0.34, // Mercury
0.72, // Venus
1.00, // Earth
1.54, // Mars
5.02, // Jupiter
9.46, // Saturn
20.11, // Uranus
30.08} // Netpune
var ssRad = []float64{ // Miles
423200.0, // Sun
1516.0, // Mercury
3760.0, // Venus
3957.0, // Earth
2104.0, // Mars
42980.0, // Jupiter
35610.0, // Saturn
15700.0, // Uranus
15260.0} // Neptune
var ssColor = []string{ // R, G, B
// Eyeballed from image
"F7730C", // Sun
"FAF8F2", // Mercury
"FFFFF2", // Venus
"0B5CE3", // Earth
"F0C61D", // Mars
"FDC791", // Jupiter
"E0C422", // Saturn
"DCF1F5", // Uranus
"39B6F7"} // Neptune
var ssImages = []string{
"sun.png",
"mercury.png",
"venus.png",
"earth.png",
"mars.png",
"jupiter.png",
"saturn.png",
"uranus.png",
"neptune.png"}
var showdisk *bool = flag.Bool("d", false, "show disk")
var canvas = svg.New(os.Stdout)
func vmap(value float64, low1 float64, high1 float64, low2 float64, high2 float64) float64 {
return low2 + (high2-low2)*(value-low1)/(high1-low1)
}
func main() {
width := 1200
height := 200
flag.Parse()
canvas.Start(width, height)
canvas.Title("Planets")
canvas.Rect(0, 0, width, height, "fill:black")
nobj := len(ssDist)
y := height / 2
margin := 100
minsize := 7.0
labeloc := height / 4
var x, r, imScale, maxh float64
var px, po int
if *showdisk {
maxh = float64(height) / minsize
} else {
maxh = float64(height) / 4.0
}
for i := 1; i < nobj; i++ {
x = vmap(ssDist[i], ssDist[1], ssDist[nobj-1], float64(margin), float64(width-margin))
r = (vmap(ssRad[i], ssRad[1], ssRad[nobj-1], minsize, maxh)) / 2
px = int(x)
if *showdisk {
po = 0
canvas.Circle(px, y, int(r), "fill:#"+ssColor[i])
} else { // show images
f, err := os.Open(ssImages[i])
if err != nil {
println("bad image file:", ssImages[i])
continue
}
defer f.Close()
p, perr := png.DecodeConfig(f)
if perr != nil {
println("bad decode:", ssImages[i])
continue
}
imScale = r / float64(p.Width)
hs := float64(p.Height) * imScale
dy := y - (int(hs) / 2) // center the image
po = int(r) / 2
canvas.Image(px, dy, int(r), int(hs), ssImages[i])
}
if ssDist[i] == 1.0 { // earth
canvas.Line(px+po, y-po, px+po, y-labeloc,
"stroke-width:1px;stroke:white")
canvas.Text(px+po, y-labeloc-10, "You are here",
"fill:white; font-size:14px; font-family:Calibri; text-anchor:middle")
}
}
canvas.End()
}
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