Initial version

earth.go

@@ -0,0 +1,230 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"image"
+	"image/color"
+	"image/color/palette"
+	"image/gif"
+	"log"
+	"math"
+	"os"
+
+	"github.com/llgcode/draw2d/draw2dimg"
+
+	"github.com/xeonx/geom"
+	"github.com/xeonx/geom/encoding/geojson"
+	"github.com/xeonx/proj4"
+)
+
+const deg2Rad = math.Pi / 180.0
+const rad2Deg = 180.0 / math.Pi
+
+func main() {
+	flag.Parse()
+
+	proj.SetFinder([]string{"C:\\OSGeo4W64\\share\\proj"})
+
+	//GeoJSON file to be animated is the first argument
+	input := flag.Arg(0)
+	if len(input) == 0 {
+		log.Fatal("Invalid input file")
+	}
+
+	log.Print(input)
+
+	file, err := os.Open(input) // For read access.
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	dec := geojson.NewDecoder(file)
+
+	var c geojson.FeatureCollection
+	if err := dec.DecodeCollection(&c); err != nil {
+		log.Fatal(err)
+	}
+
+	if len(c.Features) == 0 {
+		log.Fatal("No feature found")
+	}
+
+	projWGS84, err := proj.InitPlus("+init=epsg:4326")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	imgSize := 192.
+	r := image.Rect(0, 0, int(imgSize), int(imgSize))
+
+	var images []*image.Paletted
+	colorBackground := color.RGBA{0xff, 0xff, 0xff, 0x00}
+	colorOcean := color.RGBA{0x00, 0x66, 0xff, 0xff}
+	colorBlack := color.RGBA{0xff, 0xff, 0xff, 0xff}
+	colorLand := color.RGBA{0x00, 0x88, 0x22, 0xff}
+	colorBorder := color.RGBA{0x22, 0x22, 0x22, 0xff}
+	palette := palette.Plan9
+
+	for lon := 360.; lon >= 0; lon -= 3 {
+		projString := fmt.Sprintf("+proj=ortho +a=6378137.0 +rf=298.257223563 +towgs84=0,0,0,0,0,0,0 +lat_0=%f +lon_0=%f", 0.0, lon)
+		log.Print(projString)
+
+		projOrtho, err := proj.InitPlus(projString)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		transfo, err := proj.NewTransformation(projWGS84, projOrtho)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		img := image.NewRGBA(r)
+		gc := draw2dimg.NewGraphicContext(img)
+
+		gc.SetFillColor(colorBackground)
+		gc.MoveTo(0, 0)
+		gc.LineTo(imgSize, 0)
+		gc.LineTo(imgSize, imgSize)
+		gc.LineTo(0, imgSize)
+		gc.Close()
+		gc.FillStroke()
+
+		gc.SetFillColor(colorOcean)
+		gc.SetStrokeColor(colorBlack)
+		gc.SetLineWidth(5)
+
+		gc.Translate(float64(r.Dx())/2., float64(r.Dy())/2.)
+		gc.Scale(imgSize/(2.*6378137.), -imgSize/(2.*6378137.))
+
+		var globe []geom.Point
+		for i := -90.; i <= 90.; i += 5. {
+			globe = append(globe, geom.Point{
+				X: (lon + 90) * deg2Rad,
+				Y: i * deg2Rad,
+			})
+		}
+		for i := 90.; i > -90.; i -= 5. {
+			globe = append(globe, geom.Point{
+				X: (lon - 90) * deg2Rad,
+				Y: i * deg2Rad,
+			})
+		}
+
+		if err := transfo.TransformPoints(globe); err != nil {
+			log.Fatal(err)
+		}
+		for i := 0; i < len(globe); i++ {
+
+			if i == 0 {
+				gc.MoveTo(globe[i].X, globe[i].Y)
+			} else {
+				gc.LineTo(globe[i].X, globe[i].Y)
+			}
+		}
+
+		gc.Close()
+		gc.FillStroke()
+
+		gc.SetFillColor(colorLand)
+		gc.SetStrokeColor(colorBorder)
+		gc.SetLineWidth(5)
+
+		for i := range c.Features {
+
+			g, err := geojson.FromGeoJSON(c.Features[i].Geometry)
+			if err != nil {
+				log.Fatal(err)
+			}
+
+			g.Iterate(func(points []geom.Point) error {
+
+				for i := range points {
+					points[i].X = points[i].X * deg2Rad
+					points[i].Y = points[i].Y * deg2Rad
+				}
+
+				return transfo.TransformPoints(points)
+			})
+
+			g.Iterate(func(points []geom.Point) error {
+				var previousX int
+				var previousY int
+
+				bStarted := false
+
+				for i := 0; i < len(points); i++ {
+
+					if math.IsInf(points[i].X, 0) || math.IsInf(points[i].Y, 0) {
+						//Skip points that are out of the visible area
+						continue
+					}
+
+					if !bStarted {
+						gc.MoveTo(points[i].X, points[i].Y)
+
+						previousX = int(points[i].X * imgSize / 6378137.)
+						previousY = int(-points[i].Y * imgSize / 6378137.)
+
+						bStarted = true
+
+					} else {
+
+						currentX := int(points[i].X * imgSize / 6378137.)
+						currentY := int(-points[i].Y * imgSize / 6378137.)
+
+						if currentX != previousX || currentY != previousY {
+							gc.LineTo(points[i].X, points[i].Y)
+							previousX = currentX
+							previousY = currentY
+						}
+
+					}
+				}
+
+				if bStarted {
+					gc.Close()
+					gc.FillStroke()
+				}
+
+				return nil
+			})
+
+		}
+
+		//Copy the RGBA image to a Paletted image (usable in animated GIF)
+		paletted := image.NewPaletted(r, palette)
+		for i := 0; i < r.Dx(); i++ {
+			for j := 0; j < r.Dy(); j++ {
+
+				paletted.Set(i, j, img.At(i, j))
+
+			}
+		}
+
+		images = append(images, paletted)
+	}
+
+	//Save the animated GIF file
+	imgFile, err := os.Create("earth.gif")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	delays := make([]int, len(images))
+	for i := range delays {
+		delays[i] = 1
+	}
+
+	g := gif.GIF{
+		Image: images,
+		Delay: delays,
+	}
+
+	err = gif.EncodeAll(imgFile, &g)
+	if err != nil {
+		log.Fatal(err)
+	}
+}