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Last active July 3, 2019 21:07
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Cloud Contours
height: 480
license: gpl-3.0
redirect: https://observablehq.com/@d3/cloud-contours
<!DOCTYPE html>
<canvas width="960" height="480" style="background-image:url(cloud-fraction.png);background-size:cover;"></canvas>
<script src="https://unpkg.com/d3-contour@1"></script>
<script src="https://unpkg.com/d3-geo@1"></script>
<script src="https://unpkg.com/d3-timer@1"></script>
<script src="stack-blur.js"></script>
<script>
var canvas = document.querySelector("canvas"),
context = canvas.getContext("2d");
context.lineWidth = 2;
context.lineJoin = "round";
context.strokeStyle = "magenta";
image("cloud-fraction.png").then(function(image) {
var m = image.height,
n = image.width,
values = new Array(n * m),
contours = d3.contours().size([n, m]),
projection = d3.geoIdentity().scale(canvas.width / n),
path = d3.geoPath(projection, context);
StackBlur.R(image, 3);
for (var j = 0, k = 0; j < m; ++j) {
for (var i = 0; i < n; ++i, ++k) {
values[k] = image.data[(k << 2)] / 255;
}
}
d3.timer(function(t) {
context.clearRect(0, 0, canvas.width, canvas.height);
context.beginPath();
path(contours.thresholds([(t % 5000) / 5000])(values)[0]);
context.stroke();
});
});
function image(url) {
return new Promise(function(resolve) {
var image = new Image;
image.src = url;
image.onload = function() {
var canvas = document.createElement("canvas");
canvas.width = image.width;
canvas.height = image.height;
var context = canvas.getContext("2d");
context.drawImage(image, 0, 0);
resolve(context.getImageData(0, 0, image.width, image.height));
};
});
}
</script>
// http://www.quasimondo.com/StackBlurForCanvas Version 0.5.0. Copyright 2010 Mario Klingemann.
!function(e,t){"object"==typeof exports&&"undefined"!=typeof module?t(exports):"function"==typeof define&&define.amd?define(["exports"],t):t(e.StackBlur=e.StackBlur||{})}(this,function(e){"use strict";function t(e,t){if(!(isNaN(t)||t<1)){t|=0;var o,i,u,x,a,d,l,c,s,p,h,v=e.data,y=e.width,w=e.height,b=t+t+1,j=y-1,k=w-1,m=t+1,B=m*(m+1)/2,N=new r,S=N;for(u=1;u<b;u++)if(S=S.next=new r,u==m)var _=S;S.next=N;var g=null,M=null;l=d=0;var O=n[t],P=f[t];for(i=0;i<w;i++){for(p=c=0,s=m*(h=v[d]),c+=B*h,S=N,u=0;u<m;u++)S.r=h,S=S.next;for(u=1;u<m;u++)x=d+((j<u?j:u)<<2),c+=(S.r=h=v[x])*(m-u),p+=h,S=S.next;for(g=N,M=_,o=0;o<y;o++)v[d]=c*O>>P,c-=s,s-=g.r,x=l+((x=o+t+1)<j?x:j)<<2,p+=g.r=v[x],c+=p,g=g.next,s+=h=M.r,p-=h,M=M.next,d+=4;l+=y}for(o=0;o<y;o++){for(p=c=0,d=o<<2,s=m*(h=v[d]),c+=B*h,S=N,u=0;u<m;u++)S.r=h,S=S.next;for(a=y,u=1;u<=t;u++)d=a+o<<2,c+=(S.r=h=v[d])*(m-u),p+=h,S=S.next,u<k&&(a+=y);for(d=o,g=N,M=_,i=0;i<w;i++)x=d<<2,v[x]=c*O>>P,c-=s,s-=g.r,x=o+((x=i+m)<k?x:k)*y<<2,c+=p+=g.r=v[x],g=g.next,s+=h=M.r,p-=h,M=M.next,d+=y}return e}}function r(){this.r=0,this.next=null}var n=[512,512,456,512,328,456,335,512,405,328,271,456,388,335,292,512,454,405,364,328,298,271,496,456,420,388,360,335,312,292,273,512,482,454,428,405,383,364,345,328,312,298,284,271,259,496,475,456,437,420,404,388,374,360,347,335,323,312,302,292,282,273,265,512,497,482,468,454,441,428,417,405,394,383,373,364,354,345,337,328,320,312,305,298,291,284,278,271,265,259,507,496,485,475,465,456,446,437,428,420,412,404,396,388,381,374,367,360,354,347,341,335,329,323,318,312,307,302,297,292,287,282,278,273,269,265,261,512,505,497,489,482,475,468,461,454,447,441,435,428,422,417,411,405,399,394,389,383,378,373,368,364,359,354,350,345,341,337,332,328,324,320,316,312,309,305,301,298,294,291,287,284,281,278,274,271,268,265,262,259,257,507,501,496,491,485,480,475,470,465,460,456,451,446,442,437,433,428,424,420,416,412,408,404,400,396,392,388,385,381,377,374,370,367,363,360,357,354,350,347,344,341,338,335,332,329,326,323,320,318,315,312,310,307,304,302,299,297,294,292,289,287,285,282,280,278,275,273,271,269,267,265,263,261,259],f=[9,11,12,13,13,14,14,15,15,15,15,16,16,16,16,17,17,17,17,17,17,17,18,18,18,18,18,18,18,18,18,19,19,19,19,19,19,19,19,19,19,19,19,19,19,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24,24];e.R=t,Object.defineProperty(e,"__esModule",{value:!0})});
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