运用js绘制SVG图片

/*** Create an <svg> element and draw a pie chart into it.* 创建一个<svg>元素，并在其中绘制一个饼状图* Arguments:* 参数：*   data: an array of numbers to chart, one for each wedge of the pie.*   data：用于绘制数据的类型数组，数组的每一项都表示饼状图的一个部分*   width,height: the size of the SVG graphic, in pixels*   width，height：图形的长宽*   cx, cy, r: the center and radius of the pie*   cx, cy, r: 圆心和半径*   colors: an array of HTML color strings, one for each wedge*   colors: 包含颜色的数组，每种颜色代表了每个部分的颜色*   labels: an array of labels to appear in the legend, one for each wedge*   labels: 一个标签数组，每个部分的信息说明*   lx, ly: the upper-left corner of the chart legend* Returns: *   lx，ly: 饼状图的左上角*    An <svg> element that holds the pie chart.*    一个保存<svg>的元素*    The caller must insert the returned element into the document.*     调用者必须将返回的元素插入到文档中*/
function pieChart(data, width, height, cx, cy, r, colors, labels, lx, ly) {// This is the XML namespace for svg elementsvar svgns = "http://www.w3.org/2000/svg";    // Create the <svg> element, and specify pixel size and user coordinatesvar chart = document.createElementNS(svgns, "svg:svg");chart.setAttribute("width", width);chart.setAttribute("height", height);chart.setAttribute("viewBox", "0 0 " + width + " " + height);// Add up the data values so we know how big the pie isvar total = 0;for(var i = 0; i < data.length; i++) total += data[i];// Now figure out how big each slice of pie is. Angles in radians.var angles = []for(var i = 0; i < data.length; i++) angles[i] = data[i]/total*Math.PI*2;// Loop through each slice of pie.startangle = 0;for(var i = 0; i < data.length; i++) {// This is where the wedge endsvar endangle = startangle + angles[i];// Compute the two points where our wedge intersects the circle// These formulas are chosen so that an angle of 0 is at 12 o'clock// and positive angles increase clockwise.var x1 = cx + r * Math.sin(startangle);var y1 = cy - r * Math.cos(startangle);var x2 = cx + r * Math.sin(endangle);var y2 = cy - r * Math.cos(endangle);// This is a flag for angles larger than than a half circle// It is required by the SVG arc drawing componentvar big = 0;if (endangle - startangle > Math.PI) big = 1;// We describe a wedge with an <svg:path> element// Notice that we create this with createElementNS()var path = document.createElementNS(svgns, "path");// This string holds the path detailsvar d = "M " + cx + "," + cy +  // Start at circle center" L " + x1 + "," + y1 +     // Draw line to (x1,y1)" A " + r + "," + r +       // Draw an arc of radius r" 0 " + big + " 1 " +       // Arc details...x2 + "," + y2 +             // Arc goes to to (x2,y2)" Z";                       // Close path back to (cx,cy)// Now set attributes on the <svg:path> elementpath.setAttribute("d", d);              // Set this path path.setAttribute("fill", colors[i]);   // Set wedge colorpath.setAttribute("stroke", "black");   // Outline wedge in blackpath.setAttribute("stroke-width", "2"); // 2 units thickchart.appendChild(path);                // Add wedge to chart// The next wedge begins where this one endsstartangle = endangle;// Now draw a little matching square for the keyvar icon = document.createElementNS(svgns, "rect");icon.setAttribute("x", lx);             // Position the squareicon.setAttribute("y", ly + 30*i);icon.setAttribute("width", 20);         // Size the squareicon.setAttribute("height", 20);icon.setAttribute("fill", colors[i]);   // Same fill color as wedgeicon.setAttribute("stroke", "black");   // Same outline, too.icon.setAttribute("stroke-width", "2");chart.appendChild(icon);                // Add to the chart// And add a label to the right of the rectanglevar label = document.createElementNS(svgns, "text");label.setAttribute("x", lx + 30);       // Position the textlabel.setAttribute("y", ly + 30*i + 18);// Text style attributes could also be set via CSSlabel.setAttribute("font-family", "sans-serif");label.setAttribute("font-size", "16");// Add a DOM text node to the <svg:text> elementlabel.appendChild(document.createTextNode(labels[i]));chart.appendChild(label);               // Add text to the chart}return chart;
}

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