ホームページ > 記事 > ウェブフロントエンド > HTML5 Canvas を使用して棒グラフを描画する
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<!DOCTYPE> <html> <head> <title>Bring Your Charts to Life</title> <script type="text/javascript"> // chart sample data var arrVisitors = new Array(); arrVisitors[0] = "2007, 750"; arrVisitors[1] = "2008, 425"; arrVisitors[2] = "2009, 960"; arrVisitors[3] = "2010, 700"; arrVisitors[4] = "2011, 800"; arrVisitors[5] = "2012, 975"; arrVisitors[6] = "2013, 375"; arrVisitors[7] = "2014, 775"; var canvas; var context; // chart properties var cWidth, cHeight, cMargin, cSpace; var cMarginSpace, cMarginHeight; // bar properties var bWidth, bMargin, totalBars, maxDataValue; var bWidthMargin; // bar animation var ctr, numctr, speed; // axis property var totLabelsOnYAxis; // barchart constructor function barChart() { canvas = document.getElementById('bchart'); if (canvas && canvas.getContext) { context = canvas.getContext('2d'); } chartSettings(); drawAxisLabelMarkers(); drawChartWithAnimation(); } // initialize the chart and bar values function chartSettings() { // chart properties cMargin = 25; cSpace = 60; cHeight = canvas.height - 2 * cMargin - cSpace; cWidth = canvas.width - 2 * cMargin - cSpace; cMarginSpace = cMargin + cSpace; cMarginHeight = cMargin + cHeight; // bar properties bMargin = 15; totalBars = arrVisitors.length; bWidth = (cWidth / totalBars) - bMargin; // find maximum value to plot on chart maxDataValue = 0; for (var i = 0; i < totalBars; i++) { var arrVal = arrVisitors[i].split(","); var barVal = parseInt(arrVal[1]); if (parseInt(barVal) > parseInt(maxDataValue)) maxDataValue = barVal; } totLabelsOnYAxis = 10; context.font = "10pt Garamond"; // initialize Animation variables ctr = 0; numctr = 100; speed = 10; } // draw chart axis, labels and markers function drawAxisLabelMarkers() { context.lineWidth = "2.0"; // draw y axis drawAxis(cMarginSpace, cMarginHeight, cMarginSpace, cMargin); // draw x axis drawAxis(cMarginSpace, cMarginHeight, cMarginSpace + cWidth, cMarginHeight); context.lineWidth = "1.0"; drawMarkers(); } // draw X and Y axis function drawAxis(x, y, X, Y) { context.beginPath(); context.moveTo(x, y); context.lineTo(X, Y); context.closePath(); context.stroke(); } // draw chart markers on X and Y Axis function drawMarkers() { var numMarkers = parseInt(maxDataValue / totLabelsOnYAxis); context.textAlign = "right"; context.fillStyle = "#000";; // Y Axis for (var i = 0; i <= totLabelsOnYAxis; i++) { markerVal = i * numMarkers; markerValHt = i * numMarkers * cHeight; var xMarkers = cMarginSpace - 5; var yMarkers = cMarginHeight - (markerValHt / maxDataValue); context.fillText(markerVal, xMarkers, yMarkers, cSpace); } // X Axis context.textAlign = 'center'; for (var i = 0; i < totalBars; i++) { arrval = arrVisitors[i].split(","); name = arrval[0]; markerXPos = cMarginSpace + bMargin + (i * (bWidth + bMargin)) + (bWidth/2); markerYPos = cMarginHeight + 10; context.fillText(name, markerXPos, markerYPos, bWidth); } context.save(); // Add Y Axis title context.translate(cMargin + 10, cHeight / 2); context.rotate(Math.PI * -90 / 180); context.fillText('Visitors in Thousands', 0, 0); context.restore(); // Add X Axis Title context.fillText('Year Wise', cMarginSpace + (cWidth / 2), cMarginHeight + 30 ); } function drawChartWithAnimation() { // Loop through the total bars and draw for (var i = 0; i < totalBars; i++) { var arrVal = arrVisitors[i].split(","); bVal = parseInt(arrVal[1]); bHt = (bVal * cHeight / maxDataValue) / numctr * ctr; bX = cMarginSpace + (i * (bWidth + bMargin)) + bMargin; bY = cMarginHeight - bHt - 2; drawRectangle(bX, bY, bWidth, bHt, true); } // timeout runs and checks if bars have reached // the desired height; if not, keep growing if (ctr < numctr) { ctr = ctr + 1; setTimeout(arguments.callee, speed); } } function drawRectangle(x, y, w, h, fill) { context.beginPath(); context.rect(x, y, w, h); context.closePath(); context.stroke(); if (fill) { var gradient = context.createLinearGradient(0, 0, 0, 300); gradient.addColorStop(0, 'green'); gradient.addColorStop(1, 'rgba(67,203,36,.15)'); context.fillStyle = gradient; context.strokeStyle = gradient; context.fill(); } } </script> <noscript> This chart is unavailable because JavaScript is disabled on your computer. Please enable JavaScript and refresh this page to see the chart in action. </noscript> </head> <body onLoad="barChart();"> <canvas id="bchart" height="400" width="600">Your browser does not support HTML5 Canvas </canvas> </body> </html>
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