基于HTML5自定义文字背景生成QQ签名档

分享一款利用HTML5实现的自定义文字背景应用，首先我们可以输入需要显示的文字，并且为该文字选择一张背景图片，背景图片就像蒙版一样覆盖在文字上。点击生成QQ签名档即可将文字背景融为一体生成另外一张图片，你也可以下载这张拥有你QQ签名档的图片。

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实现的代码。

html代码：

  <canvas id="mycanvas" width="1280" height="512"></canvas>
    内容：<input type="text" id="mytxt1" value="HTML5TRICKS" />
    文字背景图：<select id="dbg">
        <option value="bg4.png">bg4.png</option>
        <option value="bg5.png">bg5.png</option>
    </select>
    <input type="button" id="send" value="生成签名档" />
    <a href="#" id="imgdownload">下载图片</a>
    <script>

        var mycanvas = document.getElementById("mycanvas");
        var mytxt1 = document.getElementById("mytxt1");
        var dbg = document.getElementById("dbg");
        var imgdownload = document.getElementById("imgdownload");
        var ctx = mycanvas.getContext("2d");

        var bg = new Image();
        var bg2 = new Image();
        bg.src = ‘imgs/bg3.png‘;
        bg2.src = ‘imgs/bg4.png‘;

        bg2.onload = ShowImg;

        function ShowImg() {
            bg2.src = ‘imgs/‘ + dbg.value;
            ctx.drawImage(bg, 0, 0, mycanvas.width, mycanvas.height);
            ctx.save();
            var fpadd = 200; //规定内间距
            var fsz = Math.ceil((mycanvas.width - fpadd * 2) / mytxt1.value.length); //根据字数计算字体大小
            ctx.font = fsz + "px hychf";
            var tw = ctx.measureText(mytxt1.value).width; //文字真实宽度
            var ftop = (mycanvas.height - fsz) / 2 - 30; //根据字体大小计算文字top
            var fleft = (mycanvas.width - tw) / 2 + 16; //根据字体大小计算文字left

            ctx.textBaseline = "top"; //设置绘制文本时的文本基线。
            var woodfill = ctx.createPattern(bg2, "repeat"); //设置图片为笔刷
            ctx.fillStyle = woodfill;
            ctx.shadowBlur = 10; //阴影程度
            ctx.shadowOffsetX = 20;
            ctx.shadowOffsetY = 20;
            ctx.shadowColor = "rgba(0,0,0,1)";
            ctx.fillText(mytxt1.value, fleft, ftop);
            ctx.lineWidth = 1;
            ctx.strokeStyle = "rgba(255,255,255,0.4)";
            ctx.strokeText(mytxt1.value, fleft, ftop);
            ctx.restore();

        }

        document.getElementById("send").onclick = ShowImg;
        imgdownload.onclick = function () {
            if (!mytxt1.value) { alert(‘请输入内容‘); return false; }
            this.href = mycanvas.toDataURL();
            this.target = "_blank";
            this.download = mytxt1.value + ".png";
        }

    </script>

css代码：

 body
        {
            background-color: #ddd;
            -webkit-user-select: none;
            font-family: hychf, "黑体";
            margin: 0;
        }
        @font-face
        {
            font-family: hychf;
            src: url(‘fonts/hychf.ttf‘);
        }
        canvas
        {
            border: 1px solid #777;
            display: block;
            margin: auto;
        }
        #imgdownload
        {
            width: 100px;
            height: 30px;
            display: block;
            text-decoration: none;
            text-align: center;
            line-height: 30px;
            border: 1px solid #000;
            border-radius: 6px;
        }

via：http://www.w2bc.com/Article/25804