Html5 Canvas 所有的畫線指令畫出來的線條都有毛邊（例如lineTo， arcTo，strokeRect），這是因為在Canvas中整數坐標值對應的位置恰巧是屏幕像素點中間的夾縫，那麼當按這樣的坐標進行線條渲染時所要用到的就是夾縫兩邊的像素點，這樣即便設定了lineWidth為1也會看到兩個像素效果的線條，解出方法原像素點+0.5進行偏移。
以下是處理前後的效果比較：
<!DOCTYPE HTML PUBLIC -//W3C//DTD HTML 4.01//EN http://www.w3.org/TR/html4/strict.dtd> <html> <head> <meta http-equiv=Content-Type content=text/html; charset=utf-8> <title>canvasTest</title> <script type=text/javascript src=http://www.pyzy.net/Demo/html5_cancas_js/excanvas.js></script> <script type=text/javascript> var MyCanvas = function(boxObj, width, height) { //序號、計數this .index = arguments.callee.prototype.Count = (arguments.callee.prototype.Count || 0) + 1; var cvs = document.createElement(canvas); cvs.id = myCanvas + this.index; cvs.width = width || 800; cvs.height = height || 600; (boxObj || document.body).appendChild(cvs); / /excanvas框架中針對ie載入canvas延時問題手動初始化物件if (typeof G_vmlCanvasManager != undefined) G_vmlCanvasManager.initElement(cvs); //2D畫布對象this.ctx = cvs.getContext(2d); /* * 繪製線條* @ops JSON對象，可依實際支援屬性擴充，範例： { lineWidth: 1,strokeStyle:'rgb(255,255,255)' } * @dotXY:{ x:0, y:0 } ||[{ x:0, y:0 },{ x:0, y:0 }] */ this.drawLine = function(dotXY, ops) { this.ctx.beginPath(); for ( var att in ops) this.ctx[att] = ops[att]; dotXY = dotXY.constructor == Object ? [dotXY || { x: 0, y: 0}] : dotXY; this.ctx.moveTo(dotXY[0].x, dotXY[0].y); for (var i = 1, len = dotXY.length; i < len; i++) this.ctx. lineTo(dotXY[i].x, dotXY[i].y); this.ctx.stroke(); }; }; window.onload=function(){ var c1 = new MyCanvas(); c1.drawLine([{ x: 10, y: 10 }, { x: 10, y: 200 }],{lineWidth:2,strokeStyle:' rgb(0,0,0)'}); c1.drawLine([{ x: 11, y: 10 }, { x: 11, y: 200 }],{lineWidth:2,strokeStyle:'rgb(255,255,255)'}); c1.drawLine([{ x: 100, y: 10 }, { x: 100, y : 200 }],{lineWidth:1,strokeStyle:'rgb(0,0,0)'}); //普通線c1.drawLine([{ x: 200.5, y: 10 }, { x: 200.5, y: 200 }],{lineWidth:1,strokeStyle:'rgb(0,0,0)'}); //+0.5偏移} </script> </head> <body> ↓ 處理的↓ 普通的↓ +0.5偏移的<br /> </body> </html>以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持VeVb武林網。