utils

Documentation

Index

• func BuildTileURL(template string, x, y, z uint64) string
• func FetchURL(url string, retries int) (io.ReadCloser, error)
• func Kernel(stdDev, mercatorScale float64) []float64
• func TileRanges(lnglatBound *geo.Bound, maxTileDim uint64) (xTileMin, xTileMax, yTileMin, yTileMax, zoomLevel uint64)

Functions

func BuildTileURL

func BuildTileURL(template string, x, y, z uint64) string

BuildTileURL will fill in a template URL of something like http://host.com/{z}/{x}/{y}.png

func FetchURL

func FetchURL(url string, retries int) (io.ReadCloser, error)

FetchURL will download the data from the URL. Make sure to close the returned io.ReadCloser

func Kernel

func Kernel(stdDev, mercatorScale float64) []float64

Kernel creates a good kernel for smoothing surfaces for the purpose of sliding. Creates a Gaussian kernel with one difference, points within on STD of the center follow f(x) = (-a / sd) * x + (a + 1/(e^0.5)). This creates a shape where we have a line from (sd, 1/e^0.5) to (0, 1/e^0.5 + addition), ie. a sharp point at the center of the Gaussian. a (the addition) is defined as sd*1.5 and can be tuned to change the sharpness of the kernel. These parameters are scaled to match the scaling caused by the mercator projection assumed by slide.

func TileRanges

func TileRanges(lnglatBound *geo.Bound, maxTileDim uint64) (xTileMin, xTileMax, yTileMin, yTileMax, zoomLevel uint64)

TileRanges returns the ranges of tiles that enclose the given latlng bound.