Html5中Canvas畫線有毛邊應(yīng)該怎么解決

發(fā)布時(shí)間：2020-05-19 15:10:45 來源：億速云閱讀：611 作者：栢白欄目：web開發(fā)

Html5 Canvas 所有的畫線指令畫出來的線條都有毛邊（比如 lineTo，arcTo，strokeRect），這是因?yàn)樵贑anvas中整數(shù)坐標(biāo)值對應(yīng)的位置恰巧是屏幕象素點(diǎn)中間的夾縫，那么當(dāng)按這樣的坐標(biāo)進(jìn)行線條渲染時(shí)所要用到的就是夾縫兩邊的象素點(diǎn)，這樣即便設(shè)置了lineWidth為1也將看到兩個(gè)象素效果的線條，解決方法原象素點(diǎn)+0.5進(jìn)行偏移。

下面是處理前后的效果比較：

<!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(jì)數(shù)  
            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加載canvas延時(shí)問題手動初始化對象  
            if (typeof G_vmlCanvasManager != "undefined") G_vmlCanvasManager.initElement(cvs);  
            //2D畫布對象  
            this.ctx = cvs.getContext("2d");  
            /* * 繪制線條  
            * @ops JSON對象，可按實(shí)際支持屬性擴(kuò)展，示例：  { 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Html5中Canvas畫線有毛邊應(yīng)該怎么解決的詳細(xì)內(nèi)容，更多請關(guān)注億速云其它相關(guān)文章！

向AI問一下細(xì)節(jié)

Html5中Canvas畫線有毛邊應(yīng)該怎么解決

猜你喜歡

最新資訊

相關(guān)推薦

相關(guān)標(biāo)簽