iaw*_*ara 9 javascript jquery html5 canvas
我希望使用百分比大小制作响应式画布,一旦用户调整画布大小相对调整大小.我能够通过使用下面的代码来缩放画布,但唯一的问题是当缩放鼠标绘图消失的窗口大小时.
<style>
body{margin:0px;padding:0px;background:#a9a9a9;}
#main{
display:block;
width:80%;
padding:50px 10%;
height:300px;
}
canvas{display:block;background:#fff;}
</style>
</head>
<body>
<div id="main" role="main">
<canvas id="paint" width="100" height="100">
< !-- Provide fallback -->
</canvas>
</div>
<script>
var c = document.getElementById('paint');
var ctx = c.getContext('2d');
var x = null;
var y;
c.onmousedown = function(e){
x = e.pageX - c.offsetLeft;
y = e.pageY - c.offsetTop;
ctx.beginPath();
ctx.moveTo(x,y);
}
c.onmouseup = function(e){
x=null;
}
c.onmousemove = function(e){
if(x==null) return;
x = e.pageX - c.offsetLeft;
y = e.pageY - c.offsetTop;
ctx.lineTo(x,y);
ctx.stroke();
}
$(document).ready( function(){
//Get the canvas &
var c = $('#paint');
var container = $(c).parent();
//Run function when browser resizes
$(window).resize( respondCanvas );
function respondCanvas(){
c.attr('width', $(container).width() ); //max width
c.attr('height', $(container).height() ); //max height
//Call a function to redraw other content (texts, images etc)
}
//Initial call
respondCanvas();
});
</script>
谢谢.
mar*_*rkE 11
调整画布大小时处理内容
如果调整画布大小,则始终会删除绘制的内容.这就是画布的行为方式.
您可以在调整大小后重绘内容,也可以将内容保存为图像数据,并在调整大小后恢复(请参阅canvas.toDataURL).
这是代码和小提琴:http://jsfiddle.net/m1erickson/V6SVz/
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<style>
body{ background-color: ivory; padding:10px; }
canvas{border:1px solid red;}
</style>
<script>
$(function(){
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
// draw some content
ctx.lineWidth=3;
ctx.fillStyle="blue";
ctx.strokeStyle="red";
ctx.rect(50,50,100,50);
ctx.fill();
ctx.stroke();
ctx.font="14px Verdana";
ctx.fillStyle="white";
ctx.fillText("Scale Me",65,75);
function saveResizeAndRedisplay(scaleFactor){
// save the canvas content as imageURL
var data=canvas.toDataURL();
// resize the canvas
canvas.width*=scaleFactor;
canvas.height*=scaleFactor;
// scale and redraw the canvas content
var img=new Image();
img.onload=function(){
ctx.drawImage(img,0,0,img.width,img.height,0,0,canvas.width,canvas.height);
}
img.src=data;
}
$("#resizer").click(function(){ saveResizeAndRedisplay(1.5); });
}); // end $(function(){});
</script>
</head>
<body>
<button id="resizer">Click to resize the canvas</button><br/>
<canvas id="canvas" width=200 height=150></canvas>
</body>
</html>
c.attr('width', $(container).width() ); //max width
c.attr('height', $(container).height() ); //max height
上面的代码相当于clearRect清除画布的代码，所以如果你想保留之前绘制的内容，就不能调整宽度和高度。作为解决方案，您可以创建一个具有所需宽度的新画布，并使用drawImage(c)c 绘制先前画布的内容，c 是画布对象。然后您必须删除画布
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