Add carto package demo code and README

carto/README.md

@@ -0,0 +1,81 @@
+# `carto` package
+
+[![Documentation](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white&style=flat)](https://pkg.go.dev/github.com/peterstace/simplefeatures/carto?tab=doc)
+
+Package carto provides cartography functionality for working with and making
+maps.
+
+This includes:
+
+  - Various projections between angular coordinates (longitude and latitude)
+    and planar coordinates (x and y).
+
+  - Earth radius definitions.
+
+See
+[godoc](https://pkg.go.dev/github.com/peterstace/simplefeatures/carto?tab=doc)
+for the full package documentation.
+
+---
+
+The following section shows supported projections. The code used to generate
+the images in this section can be found
+[here](https://github.com/peterstace/simplefeatures/tree/master/internal/cartodemo).
+
+[**Equirectangular projection**](https://en.wikipedia.org/wiki/Equirectangular_projection)
+
+Standard parallels are set to 36°N and 36°S. This configuration of the
+Equirectangular projection is also known as the Marinus (of Tyre) projection.
+
+![Equirectangular projection](../internal/cartodemo/testdata/marinus.png)
+
+[**Web Mercator projection**](https://en.wikipedia.org/wiki/Web_Mercator_projection)
+
+This is the full zoom 0 tile of the Web Mercator projection.
+
+![Web Mercator projection](../internal/cartodemo/testdata/web_mercator.png)
+
+[**Lambert Cylindrical Equal Area projection**](https://en.wikipedia.org/wiki/Lambert_cylindrical_equal-area_projection)
+
+The central meridian is set to 0°E.
+
+![Lambert Cylindrical Equal Area projection](../internal/cartodemo/testdata/lambert_cylindrical_equal_area.png)
+
+[**Sinusoidal projection**](https://en.wikipedia.org/wiki/Sinusoidal_projection)
+
+The central meridian is set to 0°E.
+
+![Sinusoidal projection](../internal/cartodemo/testdata/sinusoidal.png)
+
+[**Orthographic projection**](https://en.wikipedia.org/wiki/Orthographic_projection)
+
+Centered on North America at 45°N, 105°W.
+
+![Orthographic projection](../internal/cartodemo/testdata/orthographic_north_america.png)
+
+[**Azimuthal Equidistant projection**](https://en.wikipedia.org/wiki/Azimuthal_equidistant_projection)
+
+Centered at Sydney, Australia at 151°E, 34°S.
+
+![Azimuthal Equidistant projection](../internal/cartodemo/testdata/azimuthal_equidistant_sydney.png)
+
+[**Equidistant Conic projection**](https://en.wikipedia.org/wiki/Equidistant_conic_projection)
+
+Standard parallels are set to 30°N and 60°N. The central meridian is set to
+0°E.
+
+![Equidistant Conic projection](../internal/cartodemo/testdata/equidistant_conic.png)
+
+[**Albers Equal Area Conic projection**](https://en.wikipedia.org/wiki/Albers_projection)
+
+Standard parallels are set to 30°N and 60°N. The central meridian is set to
+0°E.
+
+![Albers Equal Area Conic projection](../internal/cartodemo/testdata/albers_equal_area_conic.png)
+
+[**Lambert Conformal Conic projection**](https://en.wikipedia.org/wiki/Lambert_conformal_conic_projection)
+
+Standard parallels are set to 30°N and 60°N. The central meridian is set to
+0°E.
+
+![Lambert Conformal Conic projection](../internal/cartodemo/testdata/lambert_conformal_conic.png)

go.mod

@@ -5,3 +5,5 @@ go 1.17
 retract v0.45.0 // Due to bug: https://github.com/peterstace/simplefeatures/pull/554
 
 require github.com/lib/pq v1.1.1
+
+require golang.org/x/image v0.23.0 // indirect

go.sum

@@ -1,2 +1,4 @@
 github.com/lib/pq v1.1.1 h1:sJZmqHoEaY7f+NPP8pgLB/WxulyR3fewgCM2qaSlBb4=
 github.com/lib/pq v1.1.1/go.mod h1:5WUZQaWbwv1U+lTReE5YruASi9Al49XbQIvNi/34Woo=
+golang.org/x/image v0.23.0 h1:HseQ7c2OpPKTPVzNjG5fwJsOTCiiwS4QdsYi5XU6H68=
+golang.org/x/image v0.23.0/go.mod h1:wJJBTdLfCCf3tiHa1fNxpZmUI4mmoZvwMCPP0ddoNKY=