利用 canvas 实现背景图片和其他图片以及文字的组合生成新图片

预览世界效果图如下：

注：以下图片中，二维码部分是我动态生成的，以及姓名和工号位置的参数需要动态替换。 

 实现思路：

利用 canvas 实现在面板上画图以及绘制文字等等。

官方文档 API 地址如下：canvas API中文网 - 中文文档 - CanvasRenderingContext2D.shadowColor

 具体实现代码逻辑如下：

ps：先说一下我是如何在前端通过 js 生成二维码图片

页面引入生成二维码的 qrcode.min.js

var QRCode;!function(){function a(a){this.mode=c.MODE_8BIT_BYTE,this.data=a,this.parsedData=[];for(var b=[],d=0,e=this.data.length;e>d;d++){var f=this.data.charCodeAt(d);f>65536?(b[0]=240|(1835008&f)>>>18,b[1]=128|(258048&f)>>>12,b[2]=128|(4032&f)>>>6,b[3]=128|63&f):f>2048?(b[0]=224|(61440&f)>>>12,b[1]=128|(4032&f)>>>6,b[2]=128|63&f):f>128?(b[0]=192|(1984&f)>>>6,b[1]=128|63&f):b[0]=f,this.parsedData=this.parsedData.concat(b)}this.parsedData.length!=this.data.length&&(this.parsedData.unshift(191),this.parsedData.unshift(187),this.parsedData.unshift(239))}function b(a,b){this.typeNumber=a,this.errorCorrectLevel=b,this.modules=null,this.moduleCount=0,this.dataCache=null,this.dataList=[]}function i(a,b){if(void 0==a.length)throw new Error(a.length+"/"+b);for(var c=0;c=f;f++){var h=0;switch(b){case d.L:h=l[f][0];break;case d.M:h=l[f][1];break;case d.Q:h=l[f][2];break;case d.H:h=l[f][3]}if(h>=e)break;c++}if(c>l.length)throw new Error("Too long data");return c}function s(a){var b=encodeURI(a).toString().replace(/\%[0-9a-fA-F]{2}/g,"a");return b.length+(b.length!=a?3:0)}a.prototype={getLength:function(){return this.parsedData.length},write:function(a){for(var b=0,c=this.parsedData.length;c>b;b++)a.put(this.parsedData[b],8)}},b.prototype={addData:function(b){var c=new a(b);this.dataList.push(c),this.dataCache=null},isDark:function(a,b){if(0>a||this.moduleCount<=a||0>b||this.moduleCount<=b)throw new Error(a+","+b);return this.modules[a][b]},getModuleCount:function(){return this.moduleCount},make:function(){this.makeImpl(!1,this.getBestMaskPattern())},makeImpl:function(a,c){this.moduleCount=4*this.typeNumber+17,this.modules=new Array(this.moduleCount);for(var d=0;d=7&&this.setupTypeNumber(a),null==this.dataCache&&(this.dataCache=b.createData(this.typeNumber,this.errorCorrectLevel,this.dataList)),this.mapData(this.dataCache,c)},setupPositionProbePattern:function(a,b){for(var c=-1;7>=c;c++)if(!(-1>=a+c||this.moduleCount<=a+c))for(var d=-1;7>=d;d++)-1>=b+d||this.moduleCount<=b+d||(this.modules[a+c][b+d]=c>=0&&6>=c&&(0==d||6==d)||d>=0&&6>=d&&(0==c||6==c)||c>=2&&4>=c&&d>=2&&4>=d?!0:!1)},getBestMaskPattern:function(){for(var a=0,b=0,c=0;8>c;c++){this.makeImpl(!0,c);var d=f.getLostPoint(this);(0==c||a>d)&&(a=d,b=c)}return b},createMovieClip:function(a,b,c){var d=a.createEmptyMovieClip(b,c),e=1;this.make();for(var f=0;f=g;g++)for(var h=-2;2>=h;h++)this.modules[d+g][e+h]=-2==g||2==g||-2==h||2==h||0==g&&0==h?!0:!1}},setupTypeNumber:function(a){for(var b=f.getBCHTypeNumber(this.typeNumber),c=0;18>c;c++){var d=!a&&1==(1&b>>c);this.modules[Math.floor(c/3)][c%3+this.moduleCount-8-3]=d}for(var c=0;18>c;c++){var d=!a&&1==(1&b>>c);this.modules[c%3+this.moduleCount-8-3][Math.floor(c/3)]=d}},setupTypeInfo:function(a,b){for(var c=this.errorCorrectLevel<<3|b,d=f.getBCHTypeInfo(c),e=0;15>e;e++){var g=!a&&1==(1&d>>e);6>e?this.modules[e][8]=g:8>e?this.modules[e+1][8]=g:this.modules[this.moduleCount-15+e][8]=g}for(var e=0;15>e;e++){var g=!a&&1==(1&d>>e);8>e?this.modules[8][this.moduleCount-e-1]=g:9>e?this.modules[8][15-e-1+1]=g:this.modules[8][15-e-1]=g}this.modules[this.moduleCount-8][8]=!a},mapData:function(a,b){for(var c=-1,d=this.moduleCount-1,e=7,g=0,h=this.moduleCount-1;h>0;h-=2)for(6==h&&h--;;){for(var i=0;2>i;i++)if(null==this.modules[d][h-i]){var j=!1;g>>e));var k=f.getMask(b,d,h-i);k&&(j=!j),this.modules[d][h-i]=j,e--,-1==e&&(g++,e=7)}if(d+=c,0>d||this.moduleCount<=d){d-=c,c=-c;break}}}},b.PAD0=236,b.PAD1=17,b.createData=function(a,c,d){for(var e=j.getRSBlocks(a,c),g=new k,h=0;h8*l)throw new Error("code length overflow. ("+g.getLengthInBits()+">"+8*l+")");for(g.getLengthInBits()+4<=8*l&&g.put(0,4);0!=g.getLengthInBits()%8;)g.putBit(!1);for(;;){if(g.getLengthInBits()>=8*l)break;if(g.put(b.PAD0,8),g.getLengthInBits()>=8*l)break;g.put(b.PAD1,8)}return b.createBytes(g,e)},b.createBytes=function(a,b){for(var c=0,d=0,e=0,g=new Array(b.length),h=new Array(b.length),j=0;j=0?p.get(q):0}}for(var r=0,m=0;mm;m++)for(var j=0;jm;m++)for(var j=0;j=0;)b^=f.G15<=0;)b^=f.G18<>>=1;return b},getPatternPosition:function(a){return f.PATTERN_POSITION_TABLE[a-1]},getMask:function(a,b,c){switch(a){case e.PATTERN000:return 0==(b+c)%2;case e.PATTERN001:return 0==b%2;case e.PATTERN010:return 0==c%3;case e.PATTERN011:return 0==(b+c)%3;case e.PATTERN100:return 0==(Math.floor(b/2)+Math.floor(c/3))%2;case e.PATTERN101:return 0==b*c%2+b*c%3;case e.PATTERN110:return 0==(b*c%2+b*c%3)%2;case e.PATTERN111:return 0==(b*c%3+(b+c)%2)%2;default:throw new Error("bad maskPattern:"+a)}},getErrorCorrectPolynomial:function(a){for(var b=new i([1],0),c=0;a>c;c++)b=b.multiply(new i([1,g.gexp(c)],0));return b},getLengthInBits:function(a,b){if(b>=1&&10>b)switch(a){case c.MODE_NUMBER:return 10;case c.MODE_ALPHA_NUM:return 9;case c.MODE_8BIT_BYTE:return 8;case c.MODE_KANJI:return 8;default:throw new Error("mode:"+a)}else if(27>b)switch(a){case c.MODE_NUMBER:return 12;case c.MODE_ALPHA_NUM:return 11;case c.MODE_8BIT_BYTE:return 16;case c.MODE_KANJI:return 10;default:throw new Error("mode:"+a)}else{if(!(41>b))throw new Error("type:"+b);switch(a){case c.MODE_NUMBER:return 14;case c.MODE_ALPHA_NUM:return 13;case c.MODE_8BIT_BYTE:return 16;case c.MODE_KANJI:return 12;default:throw new Error("mode:"+a)}}},getLostPoint:function(a){for(var b=a.getModuleCount(),c=0,d=0;b>d;d++)for(var e=0;b>e;e++){for(var f=0,g=a.isDark(d,e),h=-1;1>=h;h++)if(!(0>d+h||d+h>=b))for(var i=-1;1>=i;i++)0>e+i||e+i>=b||(0!=h||0!=i)&&g==a.isDark(d+h,e+i)&&f++;f>5&&(c+=3+f-5)}for(var d=0;b-1>d;d++)for(var e=0;b-1>e;e++){var j=0;a.isDark(d,e)&&j++,a.isDark(d+1,e)&&j++,a.isDark(d,e+1)&&j++,a.isDark(d+1,e+1)&&j++,(0==j||4==j)&&(c+=3)}for(var d=0;b>d;d++)for(var e=0;b-6>e;e++)a.isDark(d,e)&&!a.isDark(d,e+1)&&a.isDark(d,e+2)&&a.isDark(d,e+3)&&a.isDark(d,e+4)&&!a.isDark(d,e+5)&&a.isDark(d,e+6)&&(c+=40);for(var e=0;b>e;e++)for(var d=0;b-6>d;d++)a.isDark(d,e)&&!a.isDark(d+1,e)&&a.isDark(d+2,e)&&a.isDark(d+3,e)&&a.isDark(d+4,e)&&!a.isDark(d+5,e)&&a.isDark(d+6,e)&&(c+=40);for(var k=0,e=0;b>e;e++)for(var d=0;b>d;d++)a.isDark(d,e)&&k++;var l=Math.abs(100*k/b/b-50)/5;return c+=10*l}},g={glog:function(a){if(1>a)throw new Error("glog("+a+")");return g.LOG_TABLE[a]},gexp:function(a){for(;0>a;)a+=255;for(;a>=256;)a-=255;return g.EXP_TABLE[a]},EXP_TABLE:new Array(256),LOG_TABLE:new Array(256)},h=0;8>h;h++)g.EXP_TABLE[h]=1<h;h++)g.EXP_TABLE[h]=g.EXP_TABLE[h-4]^g.EXP_TABLE[h-5]^g.EXP_TABLE[h-6]^g.EXP_TABLE[h-8];for(var h=0;255>h;h++)g.LOG_TABLE[g.EXP_TABLE[h]]=h;i.prototype={get:function(a){return this.num[a]},getLength:function(){return this.num.length},multiply:function(a){for(var b=new Array(this.getLength()+a.getLength()-1),c=0;cf;f++)for(var g=c[3*f+0],h=c[3*f+1],i=c[3*f+2],k=0;g>k;k++)e.push(new j(h,i));return e},j.getRsBlockTable=function(a,b){switch(b){case d.L:return j.RS_BLOCK_TABLE[4*(a-1)+0];case d.M:return j.RS_BLOCK_TABLE[4*(a-1)+1];case d.Q:return j.RS_BLOCK_TABLE[4*(a-1)+2];case d.H:return j.RS_BLOCK_TABLE[4*(a-1)+3];default:return void 0}},k.prototype={get:function(a){var b=Math.floor(a/8);return 1==(1&this.buffer[b]>>>7-a%8)},put:function(a,b){for(var c=0;b>c;c++)this.putBit(1==(1&a>>>b-c-1))},getLengthInBits:function(){return this.length},putBit:function(a){var b=Math.floor(this.length/8);this.buffer.length<=b&&this.buffer.push(0),a&&(this.buffer[b]|=128>>>this.length%8),this.length++}};var l=[[17,14,11,7],[32,26,20,14],[53,42,32,24],[78,62,46,34],[106,84,60,44],[134,106,74,58],[154,122,86,64],[192,152,108,84],[230,180,130,98],[271,213,151,119],[321,251,177,137],[367,287,203,155],[425,331,241,177],[458,362,258,194],[520,412,292,220],[586,450,322,250],[644,504,364,280],[718,560,394,310],[792,624,442,338],[858,666,482,382],[929,711,509,403],[1003,779,565,439],[1091,857,611,461],[1171,911,661,511],[1273,997,715,535],[1367,1059,751,593],[1465,1125,805,625],[1528,1190,868,658],[1628,1264,908,698],[1732,1370,982,742],[1840,1452,1030,790],[1952,1538,1112,842],[2068,1628,1168,898],[2188,1722,1228,958],[2303,1809,1283,983],[2431,1911,1351,1051],[2563,1989,1423,1093],[2699,2099,1499,1139],[2809,2213,1579,1219],[2953,2331,1663,1273]],o=function(){var a=function(a,b){this._el=a,this._htOption=b};return a.prototype.draw=function(a){function g(a,b){var c=document.createElementNS("http://www.w3.org/2000/svg",a);for(var d in b)b.hasOwnProperty(d)&&c.setAttribute(d,b[d]);return c}var b=this._htOption,c=this._el,d=a.getModuleCount();Math.floor(b.width/d),Math.floor(b.height/d),this.clear();var h=g("svg",{viewBox:"0 0 "+String(d)+" "+String(d),width:"100%",height:"100%",fill:b.colorLight});h.setAttributeNS("http://www.w3.org/2000/xmlns/","xmlns:xlink","http://www.w3.org/1999/xlink"),c.appendChild(h),h.appendChild(g("rect",{fill:b.colorDark,width:"1",height:"1",id:"template"}));for(var i=0;d>i;i++)for(var j=0;d>j;j++)if(a.isDark(i,j)){var k=g("use",{x:String(i),y:String(j)});k.setAttributeNS("http://www.w3.org/1999/xlink","href","#template"),h.appendChild(k)}},a.prototype.clear=function(){for(;this._el.hasChildNodes();)this._el.removeChild(this._el.lastChild)},a}(),p="svg"===document.documentElement.tagName.toLowerCase(),q=p?o:m()?function(){function a(){this._elImage.src=this._elCanvas.toDataURL("image/png"),this._elImage.style.display="block",this._elCanvas.style.display="none"}function d(a,b){var c=this;if(c._fFail=b,c._fSuccess=a,null===c._bSupportDataURI){var d=document.createElement("img"),e=function(){c._bSupportDataURI=!1,c._fFail&&_fFail.call(c)},f=function(){c._bSupportDataURI=!0,c._fSuccess&&c._fSuccess.call(c)};return d.onabort=e,d.onerror=e,d.onload=f,d.src="data:image/gif;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==",void 0}c._bSupportDataURI===!0&&c._fSuccess?c._fSuccess.call(c):c._bSupportDataURI===!1&&c._fFail&&c._fFail.call(c)}if(this._android&&this._android<=2.1){var b=1/window.devicePixelRatio,c=CanvasRenderingContext2D.prototype.drawImage;CanvasRenderingContext2D.prototype.drawImage=function(a,d,e,f,g,h,i,j){if("nodeName"in a&&/img/i.test(a.nodeName))for(var l=arguments.length-1;l>=1;l--)arguments[l]=arguments[l]*b;else"undefined"==typeof j&&(arguments[1]*=b,arguments[2]*=b,arguments[3]*=b,arguments[4]*=b);c.apply(this,arguments)}}var e=function(a,b){this._bIsPainted=!1,this._android=n(),this._htOption=b,this._elCanvas=document.createElement("canvas"),this._elCanvas.width=b.width,this._elCanvas.height=b.height,a.appendChild(this._elCanvas),this._el=a,this._oContext=this._elCanvas.getContext("2d"),this._bIsPainted=!1,this._elImage=document.createElement("img"),this._elImage.style.display="none",this._el.appendChild(this._elImage),this._bSupportDataURI=null};return e.prototype.draw=function(a){var b=this._elImage,c=this._oContext,d=this._htOption,e=a.getModuleCount(),f=d.width/e,g=d.height/e,h=Math.round(f),i=Math.round(g);b.style.display="none",this.clear();for(var j=0;e>j;j++)for(var k=0;e>k;k++){var l=a.isDark(j,k),m=k*f,n=j*g;c.strokeStyle=l?d.colorDark:d.colorLight,c.lineWidth=1,c.fillStyle=l?d.colorDark:d.colorLight,c.fillRect(m,n,f,g),c.strokeRect(Math.floor(m)+.5,Math.floor(n)+.5,h,i),c.strokeRect(Math.ceil(m)-.5,Math.ceil(n)-.5,h,i)}this._bIsPainted=!0},e.prototype.makeImage=function(){this._bIsPainted&&d.call(this,a)},e.prototype.isPainted=function(){return this._bIsPainted},e.prototype.clear=function(){this._oContext.clearRect(0,0,this._elCanvas.width,this._elCanvas.height),this._bIsPainted=!1},e.prototype.round=function(a){return a?Math.floor(1e3*a)/1e3:a},e}():function(){var a=function(a,b){this._el=a,this._htOption=b};return a.prototype.draw=function(a){for(var b=this._htOption,c=this._el,d=a.getModuleCount(),e=Math.floor(b.width/d),f=Math.floor(b.height/d),g=[''],h=0;d>h;h++){g.push("");for(var i=0;d>i;i++)g.push('');g.push("")}g.push(""),c.innerHTML=g.join("");var j=c.childNodes[0],k=(b.width-j.offsetWidth)/2,l=(b.height-j.offsetHeight)/2;k>0&&l>0&&(j.style.margin=l+"px "+k+"px")},a.prototype.clear=function(){this._el.innerHTML=""},a}();QRCode=function(a,b){if(this._htOption={width:256,height:256,typeNumber:4,colorDark:"#000000",colorLight:"#ffffff",correctLevel:d.H},"string"==typeof b&&(b={text:b}),b)for(var c in b)this._htOption[c]=b[c];"string"==typeof a&&(a=document.getElementById(a)),this._android=n(),this._el=a,this._oQRCode=null,this._oDrawing=new q(this._el,this._htOption),this._htOption.text&&this.makeCode(this._htOption.text)},QRCode.prototype.makeCode=function(a){this._oQRCode=new b(r(a,this._htOption.correctLevel),this._htOption.correctLevel),this._oQRCode.addData(a),this._oQRCode.make(),this._el.title=a,this._oDrawing.draw(this._oQRCode),this.makeImage()},QRCode.prototype.makeImage=function(){"function"==typeof this._oDrawing.makeImage&&(!this._android||this._android>=3)&&this._oDrawing.makeImage()},QRCode.prototype.clear=function(){this._oDrawing.clear()},QRCode.CorrectLevel=d}();

javascript 方法如下：

var qrcode = null;
var codeValue = "";//二维码的链接地址
if(qrcode==null){
    //qrcode 页面定义的二维码图片的 DIV
	qrcode = new QRCode(document.getElementById("qrcode"), {
		width : 140,
		height : 140
    	});
}
qrcode.makeCode(codeValue);

注：这一步如果您没有这个需求可以忽略。

关于图片的合成逻辑：

	//绘制新的图片
    /**
      * picDivId 渲染新图片的容器 id
      * ewPicUrl 二维码图片src
      * cardno 和 name 是我业务内用到的参数 参数根据自身情况去使用
      *
      **/
	handleBlock(picDivId,ewmPicUrl,cardno,name) {
        // 动态创建canvas标签
        var canvas = document.createElement("canvas");
        // 设置canvas画布宽度和高度
        canvas.width = 565;
        canvas.height = 800;
        // 创建context对象
        var context = canvas.getContext("2d");
        // 用context.rect方法绘制矩形
        context.rect(0 , 0 , canvas.width , canvas.height);
        // 设置字体颜色
        context.fillStyle = "#fff";
        // 渲染
        context.fill();
        // 创建一个image对象
        var myImage = new Image();
        myImage.src = "../assets/img/manager/qrcode_bg.jpg";    //背景图片,本地或在线皆可
        // 跨域，必须
        myImage.crossOrigin = 'Anonymous';
        // 使用img的onload事件
        myImage.onload = function(){
            // 画布定义自己要插入的图片
            context.drawImage(myImage , 0 , 0 , 565 , 800);
            context.fillStyle = "#033215";
         	context.font = "bold 14px Microsoft Yahei";
         	context.fillText("姓名：",365,680);//这里设置文字所在位置的 x 和 y 
         	context.fillText("工号：",365,708);
         	context.fillStyle = "#000";
         	context.font = "14px Microsoft Yahei";
         	context.fillText(name,410,680);
         	context.fillText(cardno,410,708);
            // 创建第二个img对象
            var myImage2 = new Image();
            myImage2.src = ewmPicUrl;   //你自己本地的图片或者在线图片
            // 图片跨域，必须
            myImage2.crossOrigin = 'Anonymous';
            myImage2.onload = function(){
                context.drawImage(myImage2 , 370 ,500 , 135, 135);
                // canvas生成img图片
                //如果是生成png格式，那么就"image/png" 
                // 如果是要生成jpg格式，那么就改为"image/jpeg"
                var base64 = canvas.toDataURL("image/jpeg");
                $(picDivId).children('img')[0].src = base64;
            }
        }
    }

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