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最佳答案

Multiple images upload with info data preview

Using HTML5 and the File API

Example using URL API

The images sources will be a URL representing the Blob object
<img src="blob:null/026cceb9-edr4-4281-babb-b56cbf759a3d">

const EL_browse  = document.getElementById('browse');
const EL_preview = document.getElementById('preview');


const readImage  = file => {
if ( !(/^image\/(png|jpe?g|gif)$/).test(file.type) )
return EL_preview.insertAdjacentHTML('beforeend', `Unsupported format ${file.type}: ${file.name}<br>`);


const img = new Image();
img.addEventListener('load', () => {
EL_preview.appendChild(img);
EL_preview.insertAdjacentHTML('beforeend', `<div>${file.name} ${img.width}×${img.height} ${file.type} ${Math.round(file.size/1024)}KB<div>`);
window.URL.revokeObjectURL(img.src); // Free some memory
});
img.src = window.URL.createObjectURL(file);
}


EL_browse.addEventListener('change', ev => {
EL_preview.innerHTML = ''; // Remove old images and data
const files = ev.target.files;
if (!files || !files[0]) return alert('File upload not supported');
[...files].forEach( readImage );
});

#preview img { max-height: 100px; }

<input id="browse" type="file" multiple>
<div id="preview"></div>

Example using FileReader API

In case you need images sources as long Base64 encoded data strings
<img src="data:image/png;base64,iVBORw0KGg... ...lF/++TkSuQmCC=">

const EL_browse  = document.getElementById('browse');
const EL_preview = document.getElementById('preview');


const readImage = file => {
if ( !(/^image\/(png|jpe?g|gif)$/).test(file.type) )
return EL_preview.insertAdjacentHTML('beforeend', `<div>Unsupported format ${file.type}: ${file.name}</div>`);


const reader = new FileReader();
reader.addEventListener('load', () => {
const img  = new Image();
img.addEventListener('load', () => {
EL_preview.appendChild(img);
EL_preview.insertAdjacentHTML('beforeend', `<div>${file.name} ${img.width}×${img.height} ${file.type} ${Math.round(file.size/1024)}KB</div>`);
});
img.src = reader.result;
});
reader.readAsDataURL(file);
};


EL_browse.addEventListener('change', ev => {
EL_preview.innerHTML = ''; // Clear Preview
const files = ev.target.files;
if (!files || !files[0]) return alert('File upload not supported');
[...files].forEach( readImage );
});

#preview img { max-height: 100px; }

<input id="browse" type="file"  multiple>
<div id="preview"></div>

小开

As far as I know there is not an easy way to do this since Javascript/JQuery does not have access to the local filesystem. There are some new features in html 5 that allows you to check certain meta data such as file size but I'm not sure if you can actually get the image dimensions.

Here is an article I found regarding the html 5 features, and a work around for IE that involves using an ActiveX control. http://jquerybyexample.blogspot.com/2012/03/how-to-check-file-size-before-uploading.html

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If you can use the jQuery validation plugin you can do it like so:

Html:

<input type="file" name="photo" id="photoInput" />

JavaScript:

$.validator.addMethod('imagedim', function(value, element, param) {
var _URL = window.URL;
var  img;
if ((element = this.files[0])) {
img = new Image();
img.onload = function () {
console.log("Width:" + this.width + "   Height: " + this.height);//this will give you image width and height and you can easily validate here....


return this.width >= param
};
img.src = _URL.createObjectURL(element);
}
});

The function is passed as ab onload function.

The code is taken from here

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Here is a pure JavaScript example of picking an image file, displaying it, looping through the image properties, and then re-sizing the image from the canvas into an IMG tag and explicitly setting the re-sized image type to jpeg.

If you right click the top image, in the canvas tag, and choose Save File As, it will default to a PNG format. If you right click, and Save File as the lower image, it will default to a JPEG format. Any file over 400px in width is reduced to 400px in width, and a height proportional to the original file.

HTML

<form class='frmUpload'>
<input name="picOneUpload" type="file" accept="image/*" onchange="picUpload(this.files[0])" >
</form>


<canvas id="cnvsForFormat" width="400" height="266" style="border:1px solid #c3c3c3"></canvas>
<div id='allImgProperties' style="display:inline"></div>


<div id='imgTwoForJPG'></div>

SCRIPT

<script>


window.picUpload = function(frmData) {
console.log("picUpload ran: " + frmData);


var allObjtProperties = '';
for (objProprty in frmData) {
console.log(objProprty + " : " + frmData[objProprty]);
allObjtProperties = allObjtProperties + "<span>" + objProprty + ": " + frmData[objProprty] + ", </span>";
};


document.getElementById('allImgProperties').innerHTML = allObjtProperties;


var cnvs=document.getElementById("cnvsForFormat");
console.log("cnvs: " + cnvs);
var ctx=cnvs.getContext("2d");


var img = new Image;
img.src = URL.createObjectURL(frmData);


console.log('img: ' + img);


img.onload = function() {
var picWidth = this.width;
var picHeight = this.height;


var wdthHghtRatio = picHeight/picWidth;
console.log('wdthHghtRatio: ' + wdthHghtRatio);


if (Number(picWidth) > 400) {
var newHeight = Math.round(Number(400) * wdthHghtRatio);
} else {
return false;
};


document.getElementById('cnvsForFormat').height = newHeight;
console.log('width: 400  h: ' + newHeight);
//You must change the width and height settings in order to decrease the image size, but
//it needs to be proportional to the original dimensions.
console.log('This is BEFORE the DRAW IMAGE');
ctx.drawImage(img,0,0, 400, newHeight);


console.log('THIS IS AFTER THE DRAW IMAGE!');


//Even if original image is jpeg, getting data out of the canvas will default to png if not specified
var canvasToDtaUrl = cnvs.toDataURL("image/jpeg");
//The type and size of the image in this new IMG tag will be JPEG, and possibly much smaller in size
document.getElementById('imgTwoForJPG').innerHTML = "<img src='" + canvasToDtaUrl + "'>";
};
};


</script>

Here is a jsFiddle:

jsFiddle Pick, display, get properties, and Re-size an image file

In jsFiddle, right clicking the top image, which is a canvas, won't give you the same save options as right clicking the bottom image in an IMG tag.

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So I started experimenting with the different things that FileReader API had to offer and could create an IMG tag with a DATA URL.

Drawback: It doesn't work on mobile phones, but it works fine on Google Chrome.

$('input').change(function() {
    

var fr = new FileReader;
    

fr.onload = function() {
var img = new Image;
        

img.onload = function() {
//I loaded the image and have complete control over all attributes, like width and src, which is the purpose of filereader.
$.ajax({url: img.src, async: false, success: function(result){
$("#result").html("READING IMAGE, PLEASE WAIT...")
$("#result").html("<img src='" + img.src + "' />");
console.log("Finished reading Image");
}});
};
        

img.src = fr.result;
};
    

fr.readAsDataURL(this.files[0]);
    

});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" accept="image/*" capture="camera">
<div id='result'>Please choose a file to view it. <br/>(Tested successfully on Chrome - 100% SUCCESS RATE)</div>

(see this on a jsfiddle at http://jsfiddle.net/eD2Ez/530/)
(see the original jsfiddle that i added upon to at http://jsfiddle.net/eD2Ez/)

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Demo

Not sure if it is what you want, but just simple example:

var input = document.getElementById('input');


input.addEventListener("change", function() {
var file  = this.files[0];
var img = new Image();


img.onload = function() {
var sizes = {
width:this.width,
height: this.height
};
URL.revokeObjectURL(this.src);


console.log('onload: sizes', sizes);
console.log('onload: this', this);
}


var objectURL = URL.createObjectURL(file);


console.log('change: file', file);
console.log('change: objectURL', objectURL);
img.src = objectURL;
});

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A working jQuery validate example:

   $(function () {
$('input[type=file]').on('change', function() {
var $el = $(this);
var files = this.files;
var image = new Image();
image.onload = function() {
$el
.attr('data-upload-width', this.naturalWidth)
.attr('data-upload-height', this.naturalHeight);
}


image.src = URL.createObjectURL(files[0]);
});


jQuery.validator.unobtrusive.adapters.add('imageminwidth', ['imageminwidth'], function (options) {
var params = {
imageminwidth: options.params.imageminwidth.split(',')
};


options.rules['imageminwidth'] = params;
if (options.message) {
options.messages['imageminwidth'] = options.message;
}
});


jQuery.validator.addMethod("imageminwidth", function (value, element, param) {
var $el = $(element);
if(!element.files && element.files[0]) return true;
return parseInt($el.attr('data-upload-width')) >=  parseInt(param["imageminwidth"][0]);
});


} (jQuery));