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

拼搏现实的明天。 2023-10-12 13:12 19阅读 0赞

#### 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。

![78f285da3dc1454d91bc92999071c5fc.png][]

#### 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][canvas API_ - _ - 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<a.length&&0==a[c];)c++;this.num=new Array(a.length-c+b);for(var d=0;d<a.length-c;d++)this.num[d]=a[d+c]}function j(a,b){this.totalCount=a,this.dataCount=b}function k(){this.buffer=[],this.length=0}function m(){return"undefined"!=typeof CanvasRenderingContext2D}function n(){var a=!1,b=navigator.userAgent;return/android/i.test(b)&&(a=!0,aMat=b.toString().match(/android ([0-9]\.[0-9])/i),aMat&&aMat[1]&&(a=parseFloat(aMat[1]))),a}function r(a,b){for(var c=1,e=s(a),f=0,g=l.length;g>=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 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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;h<d.length;h++){var i=d[h];g.put(i.mode,4),g.put(i.getLength(),f.getLengthInBits(i.mode,a)),i.write(g)}for(var l=0,h=0;h<e.length;h++)l+=e[h].dataCount;if(g.getLengthInBits()>8*l)throw new Error("code length overflow. 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c={MODE_NUMBER:1,MODE_ALPHA_NUM:2,MODE_8BIT_BYTE:4,MODE_KANJI:8},d={L:1,M:0,Q:3,H:2},e={PATTERN000:0,PATTERN001:1,PATTERN010:2,PATTERN011:3,PATTERN100:4,PATTERN101:5,PATTERN110:6,PATTERN111:7},f={PATTERN_POSITION_TABLE:[[],[6,18],[6,22],[6,26],[6,30],[6,34],[6,22,38],[6,24,42],[6,26,46],[6,28,50],[6,30,54],[6,32,58],[6,34,62],[6,26,46,66],[6,26,48,70],[6,26,50,74],[6,30,54,78],[6,30,56,82],[6,30,58,86],[6,34,62,90],[6,28,50,72,94],[6,26,50,74,98],[6,30,54,78,102],[6,28,54,80,106],[6,32,58,84,110],[6,30,58,86,114],[6,34,62,90,118],[6,26,50,74,98,122],[6,30,54,78,102,126],[6,26,52,78,104,130],[6,30,56,82,108,134],[6,34,60,86,112,138],[6,30,58,86,114,142],[6,34,62,90,118,146],[6,30,54,78,102,126,150],[6,24,50,76,102,128,154],[6,28,54,80,106,132,158],[6,32,58,84,110,136,162],[6,26,54,82,110,138,166],[6,30,58,86,114,142,170]],G15:1335,G18:7973,G15_MASK:21522,getBCHTypeInfo:function(a){for(var 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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;for(var h=8;256>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 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c=j.getRsBlockTable(a,b);if(void 0==c)throw new Error("bad rs block @ typeNumber:"+a+"/errorCorrectLevel:"+b);for(var d=c.length/3,e=[],f=0;d>f;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=['<table style="border:0;border-collapse:collapse;">'],h=0;d>h;h++){g.push("<tr>");for(var i=0;d>i;i++)g.push('<td style="border:0;border-collapse:collapse;padding:0;margin:0;width:'+e+"px;height:"+f+"px;background-color:"+(a.isDark(h,i)?b.colorDark:b.colorLight)+';"></td>');g.push("</tr>")}g.push("</table>"),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;
                }
            }
        }

--------------------

如有问题，可私信咨询我或者加我文末推广微信。

[78f285da3dc1454d91bc92999071c5fc.png]: https://img-blog.csdnimg.cn/78f285da3dc1454d91bc92999071c5fc.png
[canvas API_ - _ - CanvasRenderingContext2D.shadowColor]: https://www.canvasapi.cn/CanvasRenderingContext2D/shadowColor#&examples