Using readAsDataURL() for image preview

Question

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

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]);

    }
}
}

Xotic750 Xotic750 · Accepted Answer · 2013-05-08T02:26:48

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));

On jsfiddle

Using readAsDataURL() for image preview

2 Answers