canvas实现图片js在图片上添加文字和二维码

1.效果展示：

 

2.代码实现：

// 合成分享图片
    function drawImage(qcodeUrl,inviter_name){
        var canvas = document.getElementById('myCanvas');
        var context = canvas.getContext('2d');
           // canvas.width  = document.body.clientWidth;//canvas的宽度
           canvas.width =750;//图片的宽度
           canvas.height = canvas.width*667/375;
        var swidth = canvas.width*667/375;//保存的图片宽度
        var sheight = canvas.height*667/375;
        $("#myCanvas").css({
            "height":sheight,
            "width":swidth
        });
          context.rect(0 , 0 , swidth , sheight);
          context.fill();
          var myImage = new Image();
          myImage.src = "/nwx/m/wx/images/fortuneOneAndN/invite.jpg";  //背景图片 
        //   myImage.src = "/m/wx/images/fortuneOneAndN/invite.jpg"; 
          myImage.crossOrigin = 'Anonymous';
          myImage.onload = function(){
          context.drawImage(myImage , 0, 0 , canvas.width , canvas.height,0,0,canvas.width , canvas.height);
        //    添加文字
             context.font = 'bolder 36px Microsoft YaHei';
            context.textAlign = 'right';
            context.textBaseline = 'bottom';
            var left = canvas.width*0.78;
            var top = canvas.height*0.066;
            context.fillStyle = '#fff';
            context.fillText(inviter_name, left, top);
        var myImage2 = new Image();
            myImage2.src = "data:image/jpeg;base64,"+qcodeUrl;//二维码图片
            // myImage2.crossOrigin = 'Anonymous';
            myImage2.onload = function(){
                layerUtils.iLoading(false);
                var imgWidth=canvas.width/2-150;//二维码的位置
                var imgHeight=canvas.width*0.76;
                context.drawImage(myImage2 , imgWidth , imgHeight , 300 , 270);
                var imgUrl = canvas.toDataURL("image/png");
                $("#img").attr("src",imgUrl);
            }
          }
    };

<div class="page" id="fortuneOneAndN_eQcodeInvite">
    <div id="activite_invite" >
        <!-- <h3>专属邀约活动海报生成</h3> -->
        <div class="containt_mask"></div>
        <div class="submit_containt">
            <div class="submit_info" style="text-align: left;">
                <input id="invite_name" class="inpt_conmon" type="text" placeholder="请输入姓名" onfocus="this.placeholder=''" onblur="this.placeholder='请输入姓名'" />
                <input id="phone_no" class="phone_no inpt_conmon" type="tel" pattern="\d*" maxlength="11" placeholder="输入手机号" onfocus="this.placeholder=''" onblur="this.placeholder='输入手机号'" />
                <div class="phone_code">
                    <input id="code" class="submit_code inpt_conmon" type="tel" pattern="\d*" maxlength="6" placeholder="手机验证码" onfocus="this.placeholder=''" onblur="this.placeholder='手机验证码'" />
                    <input id="getCode"class="submit_getCode inpt_conmon" type="button" value="获取验证码" />
                </div>
            </div>
            <div class="sub_btn"> 
                <a class="submit_btn">我要发起活动</a>
            </div>
        </div>
        <canvas id="myCanvas" style="z-index: 1;visibility: hidden;"></canvas>
        <div class="invite_mask" style="display: none;">
             <div class="down_mask"></div>
             <img src="../../images/wealthySpring/cancel.png" class="invite_cancel"/>
             <img id="img" style="position: fixed; top: 3%;left: 10%; width: 80%;"/>
            <div class="invite_tip">长按保存图片</div>
        </div>
    </div>
 

 
  
</div>

#activite_invite{
    position:fixed;
    top: 0;
    left: 0;
    height: 100%;
    width: 100%;
    background: url(../images/fortuneOneAndN/bg.jpg) no-repeat center center;
    background-size: 100% 100%;
}
#activite_invite .submit_containt{
    width: 80%;
    position: absolute;
    top:30%;
    left: 10%;
    color: #fff;
    text-align: center;
    border-radius: 0.16rem;
    -webkit-border-radius: 0.16rem;
    -ms-border-radius: 0.16rem;
    -o-border-radius: 0.16rem;
    -moz-border-radius: 0.16rem;
}
#activite_invite .containt_mask{
    position: absolute;
    width: 80%;
    top: 30%;
    left: 10%;
    background: #000000;
    opacity: 0.3;
    -webkit-border-radius: 0.1rem;
    -ms-border-radius: 0.1rem;
    -o-border-radius: 0.1rem;
    -moz-border-radius: 0.1rem;
}
#activite_invite .phone_no {
    width: 90%;
    margin-bottom: 0.1rem;
}
#activite_invite .inpt_conmon {
    background: #fff;
    border-radius: 0.2rem;
    padding: 0.08rem;
    border: none;
    outline: none;
}
#activite_invite .submit_code {
    width: 48%;
}
#activite_invite .submit_getCode {
    margin-left: 0.1rem;
    background: rgb(209,181,142);
    color: #fff;
    padding: 0.06rem 0.1rem;
}
#activite_invite .submit_btn {
    display: block;
    width: 80%;
    margin: 0.16rem 10% 0.12rem 10%;
    padding: o.1rem 0.2rem;
    background: rgb(209,181,142);
    font-size: 0.18rem;
    border-radius: 20px;
    font-weight: bold;
}
#activite_invite  .invite_mask {
    position: fixed;
    top: 0;
    left: 0;
    height: 100%;
    width: 100%;
    display: flex;
    align-items: center;
    justify-items: center;
}
#activite_invite .down_mask {
    position: absolute;
    height: 100%;
    width: 100%;
    background: #000;
    opacity: .5;
}
#activite_invite .invite_tip {
    text-align: center;
    z-index: 1;
    color: #fff;
    font-size: 0.18rem;
    position: fixed;
    bottom: 2.8%;
    left: 35%;
}

添加多条文字

// 合成分享图片
    function drawImage(qcodeUrl,inviter_name){
        var tipContent = "在5月31日前通过活动页面登陆,填写收件信息并参与活动,符合活动条件的客户,有机会获得一次性普通口罩1份(10枚).";
        var canvas = document.getElementById('myCanvas');
        var context = canvas.getContext('2d');
           canvas.width =750;//图片的宽度
           canvas.height = canvas.width*667/375;
        var swidth = canvas.width*667/375;//保存的图片宽度
        var sheight = canvas.height*667/375;
        $("#myCanvas").css({
            "height":sheight,
            "width":swidth
        });
          context.rect(0 , 0 , swidth , sheight);
          context.fill();
          var myImage = new Image();
          myImage.src = "/nwx/m/wx/images/healthyMind/invite.jpg";  //背景图片 
        //   myImage.src = "/m/wx/images/healthyMind/invite.jpg"; 
          myImage.crossOrigin = 'Anonymous';
          myImage.onload = function(){
          context.drawImage(myImage , 0, 0 , canvas.width , canvas.height,0,0,canvas.width , canvas.height);
        //    添加文字
             context.font = 'bolder 24px Microsoft YaHei';
            context.textAlign = 'left';
            context.textBaseline = 'bottom';
            var left = 230;
            var top = canvas.height*0.8;
            context.fillStyle = '#640000';
            // 文本换行
            var w = canvas.width-260;
            changestyle(context,tipContent,left,top,w)
            // tip2
            context.font = 'bolder 16px Microsoft YaHei';
            context.textAlign = 'left';
            context.textBaseline = 'bottom';
            var left = 230;
            var top = canvas.height*0.8+150;
             context.fillStyle = '#BE8C4B';
            context.fillText("*温馨提示:扫码参与,物流费用由**承担", left, top);
            // 邀请人姓名
            context.font = 'bolder 36px Microsoft YaHei';
            context.textAlign = 'right';
            context.textBaseline = 'bottom';
            var left = canvas.width*0.82;
            var top = canvas.height*0.066;
            context.fillStyle = '#640000';
            context.fillText(inviter_name, left, top);
        var myImage2 = new Image();
            myImage2.src = "data:image/jpeg;base64,"+qcodeUrl;//二维码图片
            // myImage2.crossOrigin = 'Anonymous';
            myImage2.onload = function(){
                layerUtils.iLoading(false);
                var imgWidth=50;//二维码的位置
                var imgHeight=canvas.height*0.8;
                context.drawImage(myImage2 , imgWidth , imgHeight , 150 , 150);
                var imgUrl = canvas.toDataURL("image/png");
                $("#img").attr("src",imgUrl);
            }
          }
    };
// 文本换行
    function changestyle(context,t,x,y,w){
        var chr = t.split("");
        var temp = "";              
        var row = [];
        for(var a = 0; a < chr.length; a++){
            if( context.measureText(temp).width < w && context.measureText(temp+(chr[a])).width <= w){
                temp += chr[a];
            }
            else{
                row.push(temp);
                temp = chr[a];
            }
        }
        row.push(temp);
        for(var b = 0; b < row.length; b++){
            context.fillText(row[b],x,y+(b+1)*36);//间隔36,类似行高
        }
    }