查找SVG元素在视口中是否可见

问题描述：

说我有一些类似于以下内容的SVG. #canvas 将应用一些转换:

Say I have some SVG that looks like the following. #canvas will have some transforms applied:

<svg id="viewport" x="0" y="0" width="100%" height="100%">
    <g id="canvas" transform="scale(0.17)">
        <image class="imageTile" x="0" y="0" width="256" height="256"/>
        <image class="imageTile" x="256" y="0" width="256" height="256"/>
        <image class="imageTile" x="0" y="256" width="256" height="256"/>
        <image class="imageTile" x="256" y="256" width="256" height="256"/>
    </g>
</svg>

#canvas 将是可拖动的，因此当我将 .imageTile 拖到视图中时，我将触发下载.

#canvas will be draggable, so when I drag a .imageTile into view, I will fire off a download.

var tiles = Y.all(".imageTile");
for (var i = 0; i < tiles.size(); i++) {
    if (the tile is visible - ??) {
        // set its xlink:href attribute
    }
}

我知道 getScreenCTM()将为我提供一个SVGMatrix对象，但是我不知道如何使用该对象来计算交集.我也知道 SVGElement.getIntersectionList()方法，但是它似乎存在一些浏览器兼容性问题.有更好的方法吗?

I know that getScreenCTM() will get me an SVGMatrix object, but I don't know how to use that to calculate the intersection. I'm also aware of the SVGElement.getIntersectionList() method, but it seems to have some browser compatibility issues. Is there a better way?

答

在 Mr的帮助下.B. Campin的SVG公开论文，我知道了:

var tile; // this is your SVG tile node

var svgroot = tile.ownerSVGElement;
var scale = svgroot.currentScale;
var vbParts = svgroot.getAttribute("viewBox").split(" ");
var vbx = parseInt(vbParts[0]);
var vby = parseInt(vbParts[1]);
var vbxu = parseInt(vbParts[2]);
var vbyu = parseInt(vbParts[3]);
var tx = svgroot.currentTranslate.x;
var ty = svgroot.currentTranslate.y;
var svgWidth = parseInt(svgroot.getAttribute("width"));
var svgHeight = parseInt(svgroot.getAttribute("height"));
var svgzoomfactor = vbxu / svgWidth;

var vpRect = svgroot.createSVGRect();
vpRect.x = parseFloat(vbx + (-tx) * (svgzoomfactor) / scale);
vpRect.y = parseFloat(vby + (-ty) * (svgzoomfactor) / scale);
vpRect.width = parseFloat(svgWidth * svgzoomfactor / scale);
vpRect.height = parseFloat(svgHeight * svgzoomfactor / scale);

if (svgroot.checkIntersection(tile, vpRect)) {
    // the tile intersects the viewport!
}

查找SVG元素在视口中是否可见

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