Download or view EqualEarthProjection.frink in plain text format
/** This program demonstrates the use of the country polygons in
Country.frink to draw a map of the world. It can be readily altered to
draw the map in your favorite projection. This demonstrates the
Equal Earth projection:
https://en.wikipedia.org/wiki/Equal_Earth_projection
https://www.equal-earth.com/equal-earth-projection.html
Original paper:
https://sci-hub.se/https://doi.org/10.1080/13658816.2018.1504949
*/
use Country.frink
g = new graphics
g.stroke[0.001]
g.font["SansSerif", "bold", 1 degree]
// Iterate through all countries.
for [code, country] = Country.getCountryList[]
{
cc = new color[randomFloat[0,1], randomFloat[0,1], randomFloat[0,1], .8]
first = true
for poly = country.borders // Iterate through polygons in a country.
{
p = new filledPolygon // This polygon is the filled country
po = new polygon // This is the outline of the country
for [long, lat] = poly // Iterate through points in polygon
{
[x,y] = latLongToXYEqualEarth[lat degree, long degree, 0 degree]
p.addPoint[x, -y]
po.addPoint[x, -y]
}
// Draw filled countries
g.color[cc]
g.add[p]
// The polygons in Country.frink are sorted so the first polygon is the
// largest. Just label the largest.
if first
{
[cx, cy] = p.getCentroid[]
g.color[0,0,0]
g.text[code, cx, cy]
}
// Draw country outlines
g.color[0.2, 0.2, 0.2, 0.8]
g.add[po]
first = false
}
}
g.invertGrays[].show[]
g.write["EqualEarth.svg", 2048, undef]
g.write["EqualEarth.png", 2048, undef]
g.write["EqualEarth.html", 1000, 500]
/** Convert a latitude, longitude, and optional center longitude (long0)
into x,y coordinates.
returns
[x ,y]
*/
latLongToXYEqualEarth[lat, long, long0 = 0 degrees] :=
{
// The EqualEarth projection uses an "auxiliary angle" theta where theta is
// given by
// sin[theta] = sqrt[3]/2 sin[lat]
// or, solving for theta:
// theta = arcsin[1/2 3^(1/2) sin[lat]]
theta = arcsin[1/2 3^(1/2) sin[lat]]
A1 = 1.340264
A2 = -0.081106
A3 = 0.000893
A4 = 0.003796
long1 = (long - long0)
x = (2 sqrt[3] long1 cos[theta]) / ( 3 (9 A4 theta^8 + 7 A3 theta^6 + 3 A2 theta^2 + A1))
y = A4 theta^9 + A3 theta^7 + A2 theta^3 + A1 theta
return [x,y]
}
Download or view EqualEarthProjection.frink in plain text format
This is a program written in the programming language Frink.
For more information, view the Frink
Documentation or see More Sample Frink Programs.
Alan Eliasen was born 20139 days, 7 hours, 14 minutes ago.