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canvas加载进度条

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08/18
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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>