使用 readAsDataURL() 进行图像预览

Using readAsDataURL() for image preview(使用 readAsDataURL() 进行图像预览)

问题描述

jsFiddle 网址:http://jsfiddle.net/Xotic750/AjtLx

jsFiddle URL: http://jsfiddle.net/Xotic750/AjtLx

整天都在处理这个问题，但我看不到问题所在.这可能是由于我对 FileReader 对象如何工作的理解狭隘，但我想做的是使用 readAsDataURL() 来获取用户选择的图像并在屏幕上的表格中预览它们.一切都在工作减去......你猜对了......预览......好吧.我想我已经接近了，因为预览会起作用，但它只显示集合的最后一张图像.例如，如果我上传了 6 张图片，那么第一行的 3 张图片会损坏，第二行的前 2 张图片会损坏，然后最后的第 6 张图片将显示预览......任何建议都非常感谢.此外，一旦这可行，它可能会帮助其他人尝试做同样的事情，因为我已经到处寻找解决这个问题的方法，但我似乎无法挖掘任何东西......

Been working on this all day and I can't see the issue. It's probably due to my narrow understanding of how FileReader objects work but what I'm trying to do is use readAsDataURL() to obtain images a user has selected and preview them on the screen in a table. Everything is working minus...you guessed it...the preview...well sort of. I'm thinking I'm close because the preview will work, BUT it only displays the last image of the set. Say for example if I uploaded 6 images then the first row of 3 images would be broken, the second row the first 2 would be broken, then the final 6th image would display the preview....Any advice greatly appreciated. Also, once this works it might help others trying to do the same thing because I've searched all over for a solution to this issue and I can't seem to dig anything up....

function PreviewImages() {
    var inputID = document.getElementById('input_clone');
    var totalImages = inputID.files.length;
    var imagesPerRow = 3;
    var numRows = totalImages / imagesPerRow;
    var row = "";
    var cell = "";
    var element1 = "";
    var elementID = "";


    for(var i = 0; i < numRows; i++){ //create rows
        row = document.getElementById('image_preview_table').insertRow(i);
        for(var ii = 0; ii < imagesPerRow; ii++){ //create cells
            cell = row.insertCell(ii);
            elementID = "img_" + ii;
            element1 = document.createElement("img");
            element1.name = elementID;
            element1.id = elementID
            cell.appendChild(element1);

            oFReader = new FileReader();

            oFReader.onload = function(oFREvent){
                var dataURI = oFREvent.target.result;
                var image = document.getElementById(elementID);
                image.src = dataURI;
            };

                oFReader.readAsDataURL(document.getElementById("input_clone").files[ii]);

    }
}
}

推荐答案

这是一个解决方案，您可能会注意到，对您的原件进行了相当多的调整以使其正常工作.

Here is a solution, quite a bit of adjustment was made to your original to get it to work, as you will probably notice.

CSS

div.rounded {
    width: 100%;
    border-style: solid;
    border-width: 1px;
    border-radius: 5px;
}
label {
    display: block;
}
input {
    display: block;
}
#previewTable {
    width: 100%;
}

HTML

<div id="imagesDiv" class="rounded">
    <label for="chooseFiles">Add Images</label>
    <input type="file" id="chooseFiles" multiple="multiple" />
    <table id="previewTable">
        <thead id="columns"></thead>
        <tbody id="previews"></tbody>
    </table>
</div>

Javascript

(function (global) {
    var imagesPerRow = 3,
        chooseFiles,
        columns,
        previews;

    function PreviewImages() {
        var row;

        Array.prototype.forEach.call(chooseFiles.files, function (file, index) {
            var cindex = index % imagesPerRow,
                oFReader = new FileReader(),
                cell,
                image;

            if (cindex === 0) {
                row = previews.insertRow(Math.ceil(index / imagesPerRow));
            }

            image = document.createElement("img");
            image.id = "img_" + index;
            image.style.width = "100%";
            image.style.height = "auto";
            cell = row.insertCell(cindex);
            cell.appendChild(image);

            oFReader.addEventListener("load", function assignImageSrc(evt) {
                image.src = evt.target.result;
                this.removeEventListener("load", assignImageSrc);
            }, false);

            oFReader.readAsDataURL(file);
        });
    }

    global.addEventListener("load", function windowLoadHandler() {
        global.removeEventListener("load", windowLoadHandler);
        chooseFiles = document.getElementById("chooseFiles");
        columns = document.getElementById("columns");
        previews = document.getElementById("previews");

        var row = columns.insertRow(-1),
            header,
            i;

        for (i = 0; i < imagesPerRow; i += 1) {
            header = row.insertCell(-1);
            header.style.width = (100 / imagesPerRow) + "%";
        }

        chooseFiles.addEventListener("change", PreviewImages, false);
    }, false);
}(window));

在 jsfiddle

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