glsl-proj4-texture

pre-calculate proj4 coordinate transformations as a texture

example

generate proj4 texture data:

`` js
var ptex = require('glsl-proj4-texture')
var tex = ptex({
src: '+proj=longlat +datum=WGS84',
dst: '+proj=geocent',
bounds: [-180,-90,180,90],
size: [256,256]
})
process.stdout.write(Buffer.from(tex.buffer))
`

in your vertex shader using glslify:

` glsl
precision highp float;
#pragma glslify: ptex = require('glsl-proj4-texture')
attribute vec2 position;
uniform sampler2D coordmap;
uniform float size;
void main () {
vec3 pt = ptex(coordmap,vec4(-180,-90,180,90),position);
gl_Position = vec4(pt.xy,0,1);
}
`

usage

`
usage: glsl-proj4-texture

Write a binary coordinate texture to stdout.

--size texture width and height in pixels. default: 128
--src proj4 source string
--dst proj4 destination string

-w --west default: -180
-s --south default: -90
-e --east default: +180
-n --north default: +90

`

js api

` js
var ptex = require('glsl-proj4-texture')
`

var data = ptex(opts)

Return a Float32Array texture from:

* opts.size - texture [width,height]. default: [128,128]
* opts.src - proj4 source string
* opts.dst - proj4 destination string
* opts.bounds - [west,south,east,north] in degrees. default: [-180,-90,180,90]

glsl api

` glsl
#pragma glslify: ptex = require('glsl-proj4-texture')
`

vec3 pt = ptex(sampler2D texture, vec4 bbox, vec2 lonlat)

Return a vec3 pt from the texture lookup on a texture created with a bbox
mapping lonlat in degrees to screen coordinates in pt`.

install

npm install glsl-proj4-texture

license

BSD