在HTML页面上绘制箭头以可视化文本跨度之间的语义链接
Kaa*_*rel 39 html javascript visualization
我有一个HTML页面,其中一些文本跨度标记为这样:
...
<span id="T2" class="Protein">p50</span>
...
<span id="T3" class="Protein">p65</span>
...
<span id="T34" ids="T2 T3" class="Positive_regulation">recruitment</span>
...
即每个跨度都有一个ID,并通过其ID引用零个或多个跨度.
我想将这些引用可视化为箭头.
两个问题:
- 如何将跨度的ID映射到跨度渲染的屏幕坐标？
- 如何绘制从一个渲染到另一个渲染的箭头？
该解决方案应该在Firefox中工作,在其他浏览器中工作是一个加号,但不是真的必要.该解决方案可以使用jQuery或其他一些轻量级JavaScript库.
Phi*_*l H 71
这引起了我的兴趣,足以产生一点点测试.代码如下,您可以看到它的实际效果
它列出了页面上的所有跨度(如果合适,可能希望将其限制为具有以T开头的ID),并使用"ids"属性来构建链接列表.使用跨距后面的画布元素,它为每个源跨距在跨距的上方和下方交替绘制圆弧箭头.
<script type="application/x-javascript">
function generateNodeSet() {
var spans = document.getElementsByTagName("span");
var retarr = [];
for(var i=0;i<spans.length; i++) {
retarr[retarr.length] = spans[i].id;
}
return retarr;
}
function generateLinks(nodeIds) {
var retarr = [];
for(var i=0; i<nodeIds.length; i++) {
var id = nodeIds[i];
var span = document.getElementById(id);
var atts = span.attributes;
var ids_str = false;
if((atts.getNamedItem) && (atts.getNamedItem('ids'))) {
ids_str = atts.getNamedItem('ids').value;
}
if(ids_str) {
retarr[id] = ids_str.split(" ");
}
}
return retarr;
}
// degrees to radians, because most people think in degrees
function degToRad(angle_degrees) {
return angle_degrees/180*Math.PI;
}
// draw a horizontal arc
// ctx: canvas context;
// inax: first x point
// inbx: second x point
// y: y value of start and end
// alpha_degrees: (tangential) angle of start and end
// upside: true for arc above y, false for arc below y.
function drawHorizArc(ctx, inax, inbx, y, alpha_degrees, upside)
{
var alpha = degToRad(alpha_degrees);
var startangle = (upside ? ((3.0/2.0)*Math.PI + alpha) : ((1.0/2.0)*Math.PI - alpha));
var endangle = (upside ? ((3.0/2.0)*Math.PI - alpha) : ((1.0/2.0)*Math.PI + alpha));
var ax=Math.min(inax,inbx);
var bx=Math.max(inax,inbx);
// tan(alpha) = o/a = ((bx-ax)/2) / o
// o = ((bx-ax)/2/tan(alpha))
// centre of circle is (bx+ax)/2, y-o
var circleyoffset = ((bx-ax)/2)/Math.tan(alpha);
var circlex = (ax+bx)/2.0;
var circley = y + (upside ? 1 : -1) * circleyoffset;
var radius = Math.sqrt(Math.pow(circlex-ax,2) + Math.pow(circley-y,2));
ctx.beginPath();
if(upside) {
ctx.moveTo(bx,y);
ctx.arc(circlex,circley,radius,startangle,endangle,1);
} else {
ctx.moveTo(bx,y);
ctx.arc(circlex,circley,radius,startangle,endangle,0);
}
ctx.stroke();
}
// draw the head of an arrow (not the main line)
// ctx: canvas context
// x,y: coords of arrow point
// angle_from_north_clockwise: angle of the line of the arrow from horizontal
// upside: true=above the horizontal, false=below
// barb_angle: angle between barb and line of the arrow
// filled: fill the triangle? (true or false)
function drawArrowHead(ctx, x, y, angle_from_horizontal_degrees, upside, //mandatory
barb_length, barb_angle_degrees, filled) { //optional
(barb_length==undefined) && (barb_length=13);
(barb_angle_degrees==undefined) && (barb_angle_degrees = 20);
(filled==undefined) && (filled=true);
var alpha_degrees = (upside ? -1 : 1) * angle_from_horizontal_degrees;
//first point is end of one barb
var plus = degToRad(alpha_degrees - barb_angle_degrees);
a = x + (barb_length * Math.cos(plus));
b = y + (barb_length * Math.sin(plus));
//final point is end of the second barb
var minus = degToRad(alpha_degrees + barb_angle_degrees);
c = x + (barb_length * Math.cos(minus));
d = y + (barb_length * Math.sin(minus));
ctx.beginPath();
ctx.moveTo(a,b);
ctx.lineTo(x,y);
ctx.lineTo(c,d);
if(filled) {
ctx.fill();
} else {
ctx.stroke();
}
return true;
}
// draw a horizontal arcing arrow
// ctx: canvas context
// inax: start x value
// inbx: end x value
// y: y value
// alpha_degrees: angle of ends to horizontal (30=shallow, >90=silly)
function drawHorizArcArrow(ctx, inax, inbx, y, //mandatory
alpha_degrees, upside, barb_length) { //optional
(alpha_degrees==undefined) && (alpha_degrees=45);
(upside==undefined) && (upside=true);
drawHorizArc(ctx, inax, inbx, y, alpha_degrees, upside);
if(inax>inbx) {
drawArrowHead(ctx, inbx, y, alpha_degrees*0.9, upside, barb_length);
} else {
drawArrowHead(ctx, inbx, y, (180-alpha_degrees*0.9), upside, barb_length);
}
return true;
}
function drawArrow(ctx,fromelem,toelem, //mandatory
above, angle) { //optional
(above==undefined) && (above = true);
(angle==undefined) && (angle = 45); //degrees
midfrom = fromelem.offsetLeft + (fromelem.offsetWidth / 2) - left - tofromseparation/2;
midto = toelem.offsetLeft + ( toelem.offsetWidth / 2) - left + tofromseparation/2;
//var y = above ? (fromelem.offsetTop - top) : (fromelem.offsetTop + fromelem.offsetHeight - top);
var y = fromelem.offsetTop + (above ? 0 : fromelem.offsetHeight) - canvasTop;
drawHorizArcArrow(ctx, midfrom, midto, y, angle, above);
}
var canvasTop = 0;
function draw() {
var canvasdiv = document.getElementById("canvas");
var spanboxdiv = document.getElementById("spanbox");
var ctx = canvasdiv.getContext("2d");
nodeset = generateNodeSet();
linkset = generateLinks(nodeset);
tofromseparation = 20;
left = canvasdiv.offsetLeft - spanboxdiv.offsetLeft;
canvasTop = canvasdiv.offsetTop - spanboxdiv.offsetTop;
for(var key in linkset) {
for (var i=0; i<linkset[key].length; i++) {
fromid = key;
toid = linkset[key][i];
var above = (i%2==1);
drawArrow(ctx,document.getElementById(fromid),document.getElementById(toid),above);
}
}
}
</script>
而你只需要在draw()函数的某个地方调用:
<body onload="draw();">
然后是一组跨度背后的画布.
<canvas style='border:1px solid red' id="canvas" width="800" height="7em"></canvas><br />
<div id="spanbox" style='float:left; position:absolute; top:75px; left:50px'>
<span id="T2">p50</span>
...
<span id="T3">p65</span>
...
<span id="T34" ids="T2 T3">recruitment</span>
</div>
根据我的意见,未来的修改:
- 展平较长箭头的顶部
- 重构能够绘制非水平箭头:为每个箭头添加一个新画布？
- 使用更好的例程来获取画布和span元素的总偏移量.
[编辑2011年12月:修复,感谢@Palo]
希望这很有趣,因为它很有趣.
- 不幸的是,在赏金结束之前,全职生活没有给我时间完成它!呃,好吧. (2认同)
- 谢谢,我希望更频繁地提出这些小挑战.几何,学习API和HTML挫折的好混合(画布还没有文本渲染).它让它变得漂亮! (2认同)
- 很好的答案。有没有人试过使用`D3.js` 来绘制箭头？ (2认同)