在前面提到Canvas是HTML5中一个重要特点,canvas功能非常强大,用photoshop可以实现的效果canvas也同样可以实现,下面我们用canvas实现基本图形的绘制。
一、Canvas标签的使用
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> </head> <body> <canvas id="1" width="200" height="200" style="border:1px solid red"></canvas> </body> </html>
可以看到Canvas就像一块画布,我们可以在这个画布上面绘制我们需要的图形。canvas 元素本身是没有绘图能力的。所有的绘制工作必须在JavaScript 内部完成。
二、画矩形
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> </head> <body> <canvas id="1" width="500" height="500" style="border:1px solid red" onmousemove="mousexy(envent)"></canvas> </body> <script type="text/javascript"> var c=document.getElementById('1'); var p=c.getContext("2d"); <span style="white-space:pre"> </span>//getContext("2d") 对象是内建的 HTML5 对象,拥有多种绘制路径、矩形、圆形、字符以及添加图像的方法。 p.fillStyle="#FF0000"; p.fillRect(0, 0, 300, 300); p.fillStyle="rgba(0,0,255,0.5)"; p.fillRect(200,200,500,500); </script> </html>
三、画线条
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> </head> <body> <canvas id="1" width="200" height="200" style="border:1px solid red" onmousemove="mousexy(envent)"></canvas> </body> <script type="text/javascript"> var c=document.getElementById('1'); var p=c.getContext("2d"); p.moveTo(10,10); p.lineTo(150,50); p.lineTo(10,50); p.stroke(); </script> </html>
四、画圆形
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> </head> <body> <canvas id="1" width="200" height="200" style="border:1px solid red" onmousemove="mousexy(envent)"></canvas> </body> <script type="text/javascript"> var c=document.getElementById('1'); var p=c.getContext("2d"); p.fillStyle="#FF0000"; p.beginPath(); p.arc(80,80,15,0,Math.PI*2,true); p.closePath(); p.fill(); </script> </html>
五、渐变
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> </head> <body> <canvas id="1" width="200" height="200" style="border:1px solid red" onmousemove="mousexy(envent)"></canvas> </body> <script type="text/javascript"> var c=document.getElementById("1"); var cxt=c.getContext("2d"); var grd=cxt.createLinearGradient(0,0,175,50); grd.addColorStop(0,"#FF0000"); grd.addColorStop(1,"#00FF00"); cxt.fillStyle=grd; cxt.fillRect(0,0,175,50); </script> </html>
六、绘制图片
<!DOCTYPE HTML> <html> <body> <canvas id="myCanvas" width="200" height="100" style="border:1px solid #c3c3c3;"> Your browser does not support the canvas element. </canvas> <script type="text/javascript"> var c=document.getElementById("myCanvas"); var cxt=c.getContext("2d"); var img=new Image() img.src="/i/eg_flower.png" cxt.drawImage(img,0,0); </script> </body> </html>
七、多边形
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> </head> <body> <canvas id="1" width="200" height="200" style="border:1px solid red" onmousemove="mousexy(envent)"></canvas> </body> <script type="text/javascript"> var c=document.getElementById('1'); var p=c.getContext("2d"); p.fillStyle="#FF0000"; p.moveTo(10,10); p.lineTo(150,50); p.lineTo(10,50); p.lineTo(20,30); p.fill(); </script> </html>
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