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html+css+js implements photo preview and upload image function example sharing

小云云Original: 2018-01-16 16:41:453594browse

When we make web pages, we often need to upload pictures. We may choose pictures or take photos to upload. If we simply use

<input type="file"/>

, although this method can also achieve the function, it may be difficult in terms of user experience. It will be a little different, so this article records the use of css+js to implement the preview and compressed upload functions after the image is selected. Some of them come from the Internet, and are recorded and organized here.

Effect preview:

1. Create index.html

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
        <title>拍照上传</title>
        <link rel="stylesheet" href="index.css"/>
        <script type=&#39;text/javascript&#39; src=&#39;index.js&#39; charset=&#39;utf-8&#39;></script>
    </head>
    <body>
         <form id="mainForm">
            <p class="content">
                <p class="label">身份证</p>
                <p class="img-area">
                    <p class="container">
                        <input type="file" id=&#39;id-face&#39; name=&#39;face&#39;  accept="image/*" />
                        <p id=&#39;face-empty-result&#39;>
                            <img style=&#39;width:4rem&#39; src="https://github.com/wangheng3751/my-resources/blob/master/images/camera.png?raw=true" alt="">
                            <p>身份证正面照</p>
                        </p>
                        <img style=&#39;width: 100%&#39; id=&#39;face-result&#39;/>
                    </p>
                    <p class="container" style=&#39;margin-top:0.5rem;&#39;>
                        <input type="file" id=&#39;id-back&#39; name=&#39;back&#39; accept="image/*" />
                        <p id=&#39;back-empty-result&#39;>
                            <img style=&#39;width:4rem&#39; src="https://github.com/wangheng3751/my-resources/blob/master/images/camera.png?raw=true" alt="">
                            <p>身份证反面照</p>
                        </p>
                        <img style=&#39;width: 100%&#39; id=&#39;back-result&#39;/>
                    </p>
                </p>
            </p>
            <p class="btn">
                提交
            </p>
         </form>
    </body>
</html>

2. Create index.css

body{
    margin: 0
}
.content{
    padding:0.5rem;
    display: flex;
    align-items: center;
    border-bottom: 1px #999 solid
}
.label{
    width:5rem;
}
.img-area{
    flex:1
}
.container{
    background-color:#e7e7e7;
    position: relative;
}
.container p{
    text-align: center;
    padding:0.5rem 0
}
.container input{
    opacity:0;
    filter:alpha(opacity=0);
    height: 100%;
    width: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 9;
}
.container p{
    font-size: 0.9rem;
    color:#999
}
.btn{
    background-color: #4363ab;
    color: #fff;
    text-align: center;
    padding: 0.5rem 1rem;
    width:80%;
    border-radius: 0.2rem;
    margin: 2rem auto;
    font-weight: 600;
    font-size: 1.2rem
}

3. Create index.js

window.onload=function(){
    document.getElementById("id-face").addEventListener("change", function(){       
        onFileChange(this,"face-result","face-empty-result")
    });
    document.getElementById("id-back").addEventListener("change", function(){       
        onFileChange(this,"back-result","back-empty-result")
    });
    document.getElementsByClassName("btn")[0].addEventListener("click", function(){       
        submit();
    });
};
/**
 * 选中图片时的处理
 * @param {*} fileObj input file元素
 * @param {*} el //选中后用于显示图片的元素ID
 * @param {*} btnel //未选中图片时显示的按钮区域ID
 */
function onFileChange(fileObj,el,btnel){
    var windowURL = window.URL || window.webkitURL;
    var dataURL;
    var imgObj = document.getElementById(el);
    document.getElementById(btnel).style.display="none";
    imgObj.style.display="block";
    if (fileObj && fileObj.files && fileObj.files[0]) {
        dataURL = windowURL.createObjectURL(fileObj.files[0]);
        imgObj.src=dataURL;
    } else {
        dataURL = fileObj.value;
        imgObj.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
        imgObj.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = dataURL;
    }
}
/**
 * 将图片压缩后返回base64格式的数据
 * @param {*} image img元素
 * @param {*} width 压缩后图片宽度
 * @param {*} height 压缩后图片高度
 * @param {*} qua //图片质量1-100
 */
function compressImageTobase64(image,width,height,qua){
    var quality = qua ? qua / 100 : 0.8;
    var canvas = document.createElement("canvas"),     
        ctx = canvas.getContext(&#39;2d&#39;);     
    var w = image.naturalWidth,     
        h = image.naturalHeight;     
    canvas.width = width||w;     
    canvas.height = height||h;     
    ctx.drawImage(image, 0, 0, w, h, 0, 0, width||w, height||h);
    var data = canvas.toDataURL("image/jpeg", quality);     
    return data;
}
//提交
function submit(){
    //1、form提交
    //document.getElementById("mainForm").submit();
    //2、压缩后ajax提交
    var face_data=compressImageTobase64(document.getElementById("face-result"),200,100,90);
    var back_data=compressImageTobase64(document.getElementById("back-result"),200,100,90);
    var formData = new FormData();  
    formData.append("face",face_data);
    formData.append("back",back_data);
    //需引入jQuery
    $.ajax({
        url:"/地址",
        type: &#39;POST&#39;,
        cache: false,
        data: formData,
        timeout:180000,
        processData: false,
        contentType: false,
        success:function(r){
        },
        error:function(r){  
        }
   });
}

Related recommendations:

Using JavaScript to preview and upload images without refreshing the page tutorial

javascript Solutions to problems found when previewing uploaded images_Image special effects

jQuery implements local preview of uploaded images_jquery

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