Draw Sector

DrawSector Illustration

The DrawSector operation renders a "pie" shape within a specified oval bounding box, starting from startAngle and sweeping through sweepAngle.

<div id="drawSectorContainer"> <canvas id="drawSectorCanvas_v1" width="600" height="500" style="border:1px solid #ccc; background: #fff; display: block; margin: 10px 0;"></canvas> </div> <script> (function() { function draw() { var canvas = document.getElementById('drawSectorCanvas_v1'); if (!canvas) { setTimeout(draw, 100); return; } var ctx = canvas.getContext('2d'); if (!ctx) return; var BLUE = '#0047AB', GRAY = '#888888', DARK_GRAY = '#444444', BLUE_TRANS = 'rgba(0, 71, 171, 0.2)'; ctx.clearRect(0, 0, 600, 500); var cx = 300, cy = 250, rx = 175, ry = 125; var startAngle = 45; var sweepAngle = 110; // Bounding Oval ctx.beginPath(); ctx.ellipse(cx, cy, rx, ry, 0, 0, 2 * Math.PI); ctx.strokeStyle = '#eee'; ctx.setLineDash([10, 10]); ctx.lineWidth = 2; ctx.stroke(); ctx.setLineDash([]); // The Sector ctx.beginPath(); ctx.moveTo(cx, cy); ctx.ellipse(cx, cy, rx, ry, 0, (startAngle * Math.PI) / 180, ((startAngle + sweepAngle) * Math.PI) / 180, false); ctx.closePath(); ctx.fillStyle = BLUE_TRANS; ctx.fill(); ctx.lineWidth = 4; ctx.strokeStyle = BLUE; ctx.stroke(); // Start Angle Indicator var sx = cx + rx * Math.cos(startAngle * Math.PI / 180); var sy = cy + ry * Math.sin(startAngle * Math.PI / 180); ctx.beginPath(); ctx.moveTo(cx, cy); ctx.lineTo(sx, sy); ctx.strokeStyle = BLUE; ctx.lineWidth = 2; ctx.stroke(); // End Angle Indicator var ex = cx + rx * Math.cos((startAngle + sweepAngle) * Math.PI / 180); var ey = cy + ry * Math.sin((startAngle + sweepAngle) * Math.PI / 180); ctx.beginPath(); ctx.moveTo(cx, cy); ctx.lineTo(ex, ey); ctx.strokeStyle = GRAY; ctx.stroke(); // Center point ctx.beginPath(); ctx.arc(cx, cy, 5, 0, 2 * Math.PI); ctx.fillStyle = DARK_GRAY; ctx.fill(); // Labels ctx.font = 'bold 18px Arial'; ctx.textAlign = 'left'; ctx.fillStyle = BLUE; ctx.fillText('startAngle: ' + startAngle + '°', sx + 10, sy + 15); ctx.textAlign = 'left'; ctx.fillStyle = DARK_GRAY; ctx.fillText('sweepAngle: ' + sweepAngle + '°', ex - 120, ey + 65); ctx.textAlign = 'center'; ctx.font = '14px Arial'; ctx.fillStyle = GRAY; ctx.fillText('Center (cx, cy)', cx, cy - 15); } if (document.readyState === 'complete') { draw(); } else { window.addEventListener('load', draw); setTimeout(draw, 500); } })(); </script>