[英]html5 canvas venn 3 circles
在畫布上進行維恩圖創建的工作。 我正在嘗試為每個交叉點和每個圓使用不同的顏色。 雖然我可以使用重疊的圓來做到這一點,但我需要使每個相交點都是獨立的,以便在懸停時要為每個相交點操縱顏色。
問題是我可以完成所有部分,但最后的部分要重疊。 這是現有解決方案的圖像: venn diagram image 。 需要標記/顯示黃色和藍色圓圈的重疊,而不會影響底部圓圈的重疊。 到目前為止,這是我所擁有的(我意識到這不是最簡單的方法,正在着手簡化):
<script>
window.LENS = {};
LENS.init = function(){
var self = this;
this.canvas = document.getElementById('canvas');
this.ctx = canvas.getContext('2d');
this.width = window.innerWidth;
this.height = window.innerHeight;
this.canvas.width = window.innerWidth;
this.canvas.height = window.innerHeight+50; //compensate for margin
this.drawLens(this.ctx, this.width, this.height);
}
LENS.drawLens = function (ctx, windowWidth, windowHeight){
var self = this;
var radius=windowWidth/5.25;
var circle1={x:windowWidth/2.5, y:windowHeight/3, r:radius, color: 'rgb(130,205,240)'};
var circle2={x:windowWidth/1.75, y:windowHeight/3, r:radius, color: 'rgb(255,240,180)'};
var circle3={x:circle1.x+circle1.r/2, y:circle1.y+circle1.r/1.2, r:radius, color: 'rgb(245,120,125)'}; //dividing by 1.2 for visual purposes. radius would be centered, but provides optical illusiion
var intersect1={color:'rgb(0,170,145)'};
var intersect2={color:'rgb(130,70,110)'};
var intersect3={color:'rgb(255,160,75)'};
var intersectCenter={color:'rgb(55,55,55)'};
//draw circle1
//ctx.save(); //important or we lose the context and will hold all drawing
ctx.beginPath();
ctx.arc(circle1.x, circle1.y, circle1.r, 0, 2*Math.PI, false);
ctx.fillStyle=circle1.color;
ctx.strokeStyle=circle1.color;
ctx.stroke();
ctx.fill();
//intersection1 top
ctx.beginPath();
ctx.fillStyle=intersect1.color;
ctx.strokeStyle=intersect1.color;
ctx.globalCompositeOperation='source-atop';
ctx.arc(circle2.x,circle2.y,circle2.r, 0, 2*Math.PI, false);
ctx.fill();
//intersection2 top
ctx.beginPath();
ctx.fillStyle=intersect2.color;
ctx.strokeStyle=intersect2.color;
ctx.globalCompositeOperation='source-atop';
ctx.arc(circle3.x,circle3.y,circle3.r, 0, 2*Math.PI, false);
ctx.fill();
//intersect Center
ctx.beginPath();
ctx.globalCompositeOperation='source-atop'
ctx.arc(circle2.x, circle2.y, circle2.r, 0, 2*Math.PI, false);
ctx.fillStyle=intersectCenter.color;
ctx.strokeStyle=intersectCenter.color;
ctx.stroke();
ctx.fill();
//draw intersection3 bottom
ctx.beginPath();
ctx.fillStyle=intersect3.color;
ctx.strokeStyle=intersect3.color;
ctx.globalCompositeOperation='destination-over';
ctx.arc(circle2.x, circle2.y, circle2.r, 0, 2*Math.PI, false);
ctx.fill();
ctx.stroke();
//intersection 3
ctx.beginPath();
ctx.fillStyle=intersect3.color;
ctx.strokeStyle=intersect3.color;
ctx.globalCompositeOperation='destination-in';
ctx.arc(circle3.x, circle3.y, circle3.r, 0, 2*Math.PI, false);
ctx.fill();
ctx.stroke();
//circle3
ctx.beginPath();
ctx.fillStyle=circle3.color;
ctx.globalCompositeOperation='destination-over';
ctx.arc(circle3.x,circle3.y,circle3.r, 0, 2*Math.PI, false);
ctx.fill();
//redraw circle 1
ctx.beginPath();
ctx.globalCompositeOperation='destination-over';
ctx.arc(circle1.x, circle1.y, circle1.r, 0, 2*Math.PI, false);
ctx.fillStyle=circle1.color;
ctx.strokeStyle=circle1.color;
ctx.stroke();
ctx.fill();
//redraw circle 2
ctx.beginPath();
ctx.globalCompositeOperation='destination-over'
ctx.arc(circle2.x, circle2.y, circle2.r, 0, 2*Math.PI, false);
ctx.fillStyle=circle2.color;
ctx.strokeStyle=circle2.color;
ctx.stroke();
ctx.fill();
}
</script>
您可以使用屏幕外畫布,該畫布使用合成功能來創建維恩聯合。
如果將合成設置為“源入”,則任何新工程圖將僅在現有工程圖和新工程圖重疊的位置顯示。 其他所有內容將被清除(透明)。
“源入”合成是繪制維恩並集的理想選擇,因為只有2個圓的交點才能幸存。
如果將合成設置為“目標輸出”,則任何新工程圖都會清除新工程圖重疊的工程圖。 (這就像一個“擦除”操作)
此偽代碼將顯示您的藍色和黃色圓圈的並集(所有內容都將被刪除):
此偽代碼將顯示您遇到麻煩的頂部藍黃色聯合:
代碼和演示: http : //jsfiddle.net/m1erickson/XLhT9/
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<style>
body{ background-color: white; }
canvas{border:1px solid red;}
</style>
<script>
$(function(){
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var canvas1=document.createElement("canvas");
var ctx1=canvas1.getContext("2d");
var circleBlue={x:50,y:50,r:40};
var circleYellow={x:100,y:50,r:40};
var circleRed={x:75,y:85,r:40};
drawCircle(ctx,circleRed,"salmon");
drawCircle(ctx,circleYellow,"lemonchiffon");
drawCircle(ctx,circleBlue,"lightblue");
$r=$("#r")[0];
$y=$("#y")[0];
$b=$("#b")[0];
$by=$("#by")[0];
$br=$("#br")[0];
$yr=$("#yr")[0];
$byNotR=$("#byNotR")[0];
$brNotY=$("#brNotY")[0];
$yrNotB=$("#yrNotB")[0];
$yrb=$("#yrb")[0];
$r.checked=true;
$y.checked=true;
$b.checked=true;
$(":checkbox").change(function(){drawAll()});
function drawIntersect(a,b,c,notC,color){
ctx1.clearRect(0,0,canvas1.width,canvas1.height);
ctx1.save();
// a
drawCircle(ctx1,a,color);
// b
ctx1.globalCompositeOperation="source-in";
drawCircle(ctx1,b,color);
// c
if(c){drawCircle(ctx1,c,color); }
// notC
ctx1.globalCompositeOperation="destination-out";
if(notC){ drawCircle(ctx1,notC,color); }
ctx1.restore();
ctx.drawImage(canvas1,0,0);
}
function drawCircle(ctx,circle,color){
ctx.beginPath();
ctx.arc(circle.x,circle.y,circle.r,0,Math.PI*2);
ctx.closePath();
ctx.fillStyle=color;
ctx.fill();
}
function drawAll(){
ctx.clearRect(0,0,canvas.width,canvas.height);
if($r.checked){drawCircle(ctx,circleRed,"salmon");}
if($y.checked){drawCircle(ctx,circleYellow,"lemonchiffon");}
if($b.checked){drawCircle(ctx,circleBlue,"lightblue");}
if($by.checked){drawIntersect(circleBlue,circleYellow,null,null,"green");}
if($br.checked){drawIntersect(circleBlue,circleRed,null,null,"blue");}
if($yr.checked){drawIntersect(circleYellow,circleRed,null,null,"red");}
if($byNotR.checked){drawIntersect(circleBlue,circleYellow,null,circleRed,"green");}
if($brNotY.checked){drawIntersect(circleBlue,circleRed,null,circleYellow,"blue");}
if($yrNotB.checked){drawIntersect(circleYellow,circleRed,null,circleBlue,"red");}
if($yrb.checked){drawIntersect(circleYellow,circleRed,circleBlue,null,"black");}
}
}); // end $(function(){});
</script>
</head>
<body>
<input type="checkbox" id="r">Red Circle<br>
<input type="checkbox" id="y">Yellow Circle<br>
<input type="checkbox" id="b">Blue Circle<br>
<input type="checkbox" id="by">Blue+Yellow<br>
<input type="checkbox" id="br">Blue+Red<br>
<input type="checkbox" id="yr">Yellow+Red<br>
<input type="checkbox" id="byNotR">Blue+Yellow-Red<br>
<input type="checkbox" id="brNotY">Blue+Red-Yellow<br>
<input type="checkbox" id="yrNotB">Yellow+Red-Blue<br>
<input type="checkbox" id="yrb">Yellow+Red+Blue<br>
<canvas id="canvas" width=150 height=150></canvas>
</body>
</html>
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