archive-gh-me/go-staticmaps
1
0
Fork 0
mirror of https://github.com/flopp/go-staticmaps.git synced 2025-12-08 18:26:36 +00:00
Code Issues Projects Releases Wiki Activity

Fix latitude centering. Closes #44. (#45)

Browse Source
This commit is contained in:
Florian Pigorsch 2020-11-14 16:17:22 +01:00 committed by GitHub
parent 112a0c57b9
commit 4b82c94de8
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 14 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
context.go
View File

@ -15,6 +15,7 @@ import (
"math"
"github.com/fogleman/gg"
"github.com/golang/geo/s1"
"github.com/golang/geo/s2"
)
@ -242,10 +243,21 @@ func (m *Context) determineZoom(bounds s2.Rect, center s2.LatLng) int {
return 15
}
// determineCenter computes a point that is visually centered in Mercator projection
func (m *Context) determineCenter(bounds s2.Rect) s2.LatLng {
latLo := bounds.Lo().Lat.Radians()
latHi := bounds.Hi().Lat.Radians()
yLo := math.Log((1+math.Sin(latLo))/(1-math.Sin(latLo))) / 2
yHi := math.Log((1+math.Sin(latHi))/(1-math.Sin(latHi))) / 2
lat := s1.Angle(math.Atan(math.Sinh((yLo + yHi) / 2)))
lng := bounds.Center().Lng
return s2.LatLng{Lat: lat, Lng: lng}
}
func (m *Context) determineZoomCenter() (int, s2.LatLng, error) {
bounds := m.determineBounds()
if m.hasBoundingBox && !m.boundingBox.IsEmpty() {
center := m.boundingBox.Center()
center := m.determineCenter(m.boundingBox)
return m.determineZoom(m.boundingBox, center), center, nil
} else if m.hasCenter {
if m.hasZoom {
@ -253,7 +265,7 @@ func (m *Context) determineZoomCenter() (int, s2.LatLng, error) {
}
return m.determineZoom(bounds, m.center), m.center, nil
} else if !bounds.IsEmpty() {
center := bounds.Center()
center := m.determineCenter(bounds)
if m.hasZoom {
return m.zoom, center, nil
}