sweden.poly rendered using gfx.

gfx-sweden.go

package main

import (
	"io"
	"net/http"
	"strconv"
	"text/scanner"

	"github.com/peterhellberg/gfx"
)

const rawurl = "https://download.geofabrik.de/europe/sweden.poly"

func main() {
	resp, err := http.Get(rawurl)
	if err != nil || resp.StatusCode != http.StatusOK {
		return
	}

	p := scanPoly(resp.Body).Project(gfx.IM.
		Moved(gfx.V(303, 258)).
		ScaledXY(gfx.V(320, 320), gfx.V(36, -36)))

	dst := gfx.NewImage(640, 640, gfx.BlockColorBlack.Dark)

	p.Fill(dst, gfx.BlockColorBlue.Medium)

	for i := 1; i < len(p); i++ {
		gfx.DrawLine(dst, p[i-1], p[i], 1, gfx.BlockColorBlue.Light)
	}

	gfx.SavePNG("gfx-sweden.png", dst)
}

func scanPoly(r io.Reader) (p gfx.Polygon) {
	var s scanner.Scanner

	s.Init(r)

	var floats []float64

	for tok := s.Scan(); tok != scanner.EOF; tok = s.Scan() {
		switch tok {
		case scanner.Float:
			if f, err := strconv.ParseFloat(s.TokenText(), 64); err == nil {
				floats = append(floats, f)
			}
		}
	}

	for i := len(floats) - 2; i >= 0; i -= 2 {
		p = append(p, gfx.V(floats[i], floats[i+1]))
	}

	return p
}