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<!DOCTYPE html> <html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Progress Bar</title> <script type="text/javascript"> var i = 0; var res = 0; var context = null; var total_width = 300;/*宽度*/ var total_height = 34;/*高度*/ var initial_x = 20; var initial_y = 20; var radius = total_height/2; window.onload = function() { var elem = document.getElementById(‘myCanvas‘); if (!elem || !elem.getContext) { return; } context = elem.getContext(‘2d‘); if (!context) { return; } // set font context.font = "16px Verdana"; // Blue gradient for progress bar var progress_lingrad = context.createLinearGradient(0,initial_y+total_height,0,0); progress_lingrad.addColorStop(0, ‘#4DA4F3‘);/*加载完下面的颜色*/ progress_lingrad.addColorStop(0.4, ‘#ADD9FF‘);/*加载完中间的颜色*/ progress_lingrad.addColorStop(1, ‘#9ED1FF‘);/*加载完上面的颜色*/ context.fillStyle = progress_lingrad; //draw(); res = setInterval(draw, 30); } function draw() { i+=1; // Clear everything before drawing context.clearRect(initial_x-5,initial_y-5,total_width+15,total_height+15); progressLayerRect(context, initial_x, initial_y, total_width, total_height, radius); progressBarRect(context, initial_x, initial_y, i, total_height, radius, total_width); progressText(context, initial_x, initial_y, i, total_height, radius, total_width ); if (i>=total_width) { clearInterval(res); } } function roundRect(ctx, x, y, width, height, radius) { ctx.beginPath(); ctx.moveTo(x + radius, y); ctx.lineTo(x + width - radius, y); ctx.arc(x+width-radius, y+radius, radius, -Math.PI/2, Math.PI/2, false); ctx.lineTo(x + radius, y + height); ctx.arc(x+radius, y+radius, radius, Math.PI/2, 3*Math.PI/2, false); ctx.closePath(); ctx.fill(); } function roundInsetRect(ctx, x, y, width, height, radius) { ctx.beginPath(); // Draw huge anti-clockwise box ctx.moveTo(1000, 1000); ctx.lineTo(1000, -1000); ctx.lineTo(-1000, -1000); ctx.lineTo(-1000, 1000); ctx.lineTo(1000, 1000); ctx.moveTo(x + radius, y); ctx.lineTo(x + width - radius, y); ctx.arc(x+width-radius, y+radius, radius, -Math.PI/2, Math.PI/2, false); ctx.lineTo(x + radius, y + height); ctx.arc(x+radius, y+radius, radius, Math.PI/2, 3*Math.PI/2, false); ctx.closePath(); ctx.fill(); } function progressLayerRect(ctx, x, y, width, height, radius) { ctx.save(); // Set shadows to make some depth ctx.shadowOffsetX = 2; ctx.shadowOffsetY = 2; ctx.shadowBlur = 5; ctx.shadowColor = ‘#666‘; // Create initial grey layer ctx.fillStyle = ‘rgba(189,189,189,1)‘; roundRect(ctx, x, y, width, height, radius); // Overlay with gradient ctx.shadowColor = ‘rgba(0,0,0,0)‘ var lingrad = ctx.createLinearGradient(0,y+height,0,0); lingrad.addColorStop(0, ‘rgba(255,255,255, 0.1)‘); lingrad.addColorStop(0.4, ‘rgba(255,255,255, 0.7)‘); lingrad.addColorStop(1, ‘rgba(255,255,255,0.4)‘); ctx.fillStyle = lingrad; roundRect(ctx, x, y, width, height, radius); ctx.fillStyle = ‘white‘; //roundInsetRect(ctx, x, y, width, height, radius); ctx.restore(); } function progressBarRect(ctx, x, y, width, height, radius, max) { // var to store offset for proper filling when inside rounded area var offset = 0; ctx.beginPath(); if (width<radius) { offset = radius - Math.sqrt(Math.pow(radius,2)-Math.pow((radius-width),2)); ctx.moveTo(x + width, y+offset); ctx.lineTo(x + width, y+height-offset); ctx.arc(x + radius, y + radius, radius, Math.PI - Math.acos((radius - width) / radius), Math.PI + Math.acos((radius - width) / radius), false); } else if (width+radius>max) { offset = radius - Math.sqrt(Math.pow(radius,2)-Math.pow((radius - (max-width)),2)); ctx.moveTo(x + radius, y); ctx.lineTo(x + width, y); ctx.arc(x+max-radius, y + radius, radius, -Math.PI/2, -Math.acos((radius - (max-width)) / radius), false); ctx.lineTo(x + width, y+height-offset); ctx.arc(x+max-radius, y + radius, radius, Math.acos((radius - (max-width)) / radius), Math.PI/2, false); ctx.lineTo(x + radius, y + height); ctx.arc(x+radius, y+radius, radius, Math.PI/2, 3*Math.PI/2, false); } else { ctx.moveTo(x + radius, y); ctx.lineTo(x + width, y); ctx.lineTo(x + width, y + height); ctx.lineTo(x + radius, y + height); ctx.arc(x+radius, y+radius, radius, Math.PI/2, 3*Math.PI/2, false); } ctx.closePath(); ctx.fill(); if (width<max-1) { ctx.save(); ctx.shadowOffsetX = 1; ctx.shadowBlur = 1; ctx.shadowColor = ‘#666‘; if (width+radius>max) offset = offset+1; ctx.fillRect(x+width,y+offset,1,total_height-offset*2); ctx.restore(); } } function progressText(ctx, x, y, width, height, radius, max) { ctx.save(); ctx.fillStyle = ‘white‘; var text = Math.floor(width/max*100)+"%"; var text_width = ctx.measureText(text).width; var text_x = x+width-text_width-radius/2; if (width<=radius+text_width) { text_x = x+radius/2; } ctx.fillText(text, text_x, y+22); ctx.restore(); } </script> </head> <body> <p> <canvas id="myCanvas" width="800" height="150"></canvas> </p> </body> </html>
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原文地址：http://www.cnblogs.com/binmengxue/p/5461551.html
