Image preview before upload in IE and Chrome

Question

I am trying to design a module in which I would like to show a preview of the image to the user before he uploads the image to database.

I have found a solution which wo

Answer 1

I concur with the nay-sayers who have already answered - local files are off limits by design.

But, if you are really committed to this preview-before-upload feature, and willing to include some bumpy UX, you might circumvent the local/server question and...

...use an accompanying AIR application to handle image uploading for your web app.

• Create a simple AIR application that allow users to select local images and displays them in thumbnails without uploading them.

• You can check to see if user's have the app installed, at which point you can prompt them to install or launch it if it's already installed (see here for more on that). You could allow them to opt out and use a fallback upload system without thumbnail previews as well.

• Once the images are selected and reviewed (or even resized or otherwise processed), the AIR app could upload them to your server directly.

It's insane, I know, and probably doesn't fit your skill-set or expectations (based on the tags on this question) but I think it would work.

Answer 2

Use jQuery ajax to solve your problem.

$.ajax({
    type: "post",
    url: "serverURL?randomParam="+(Math.random() * 1000),
    cache: false,               
    data: null,
    success: function(json){
        try{            
            var obj = JSON.parse(json);                                             
            if(obj[0].IMAGE!=null){                             
                $("#captchaImage").attr("src", obj[0].IMAGE); 
            }               
        }catch(e) {     
            showMessage("E1");  
        }
    },
    error: function(){
    }
});

Answer 3

Try this for IE < 10:

<style type="text/css">
#imgPreview {
    width:320px;
    height:280px;
    filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale);
}
</style>

<h2>Preview images for MS-IE &lt; 10</h2>
<form id="form1" runat="server">
        <input type="file" onchange='document.getElementById("imgPreview").filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src=this.value' />
        <div id="imgPreview"></div>
</form>

Fiddle: http://jsfiddle.net/Sme2L/5/

Answer 4

This will not work in any other browser other than firefox because the FileReader object you are using is not a js standered, it is a class very specific to FireFox. As per web standard browser scripts(javascript) will not have security permission to read contents of any system resources(files).

In IE you can try to get some ActiveXObject(FileSystemObject) help access the file system contents.

Answer 5

There's no cross-browser solution (even FileReader needs certain permissions in Firefox), only some workarounds for ie and firefox.

You should do the conventional way, upload the image to a temp file and delete/save it depending on user confirmation

Hope this helps

Answer 6

There is no cross platform way to accomplish this using only HTML/JavaScript. It is possible, however, using a very basic programmatic approach:

Step 1: Binding to Blur
Bind a "blur" event to your file input field, like so:

$("#input_field").blur(function(event){
    alert("Blur!");
});

Step 2: Server-Side Thumbnailing
You're going to have to write a small application/route on your server side application that simply accepts a form that contains in input file, and generates a temporary output file. You could even just temporarily store the filedata in your database, rather than write individual files to disk; the implementation is up to you. When this route receives a request, it should thumbnail the image, and then return a path to that thumbnail

Step 3: AJAX
First, choose one of the many available jQuery "AJAX Upload" libraries to make the form that contains your file upload it via AJAX. Apply that library to the form(For the examples below, I'll use ajaxForm.), and then modify your blur:

// AJAX the form
$("#your_form").ajaxForm({
    success: function(response){
        // Insert your returned thumbnail into your DOM.
    }
});

// Modify the blur
$("#input_field").blur(function(event){
    $("#input_field").closest("form").submit();
});

Issues:
There will be issues with the approach above. Making your form AJAX will mean submitting it regularly will break - not to mention that the thumbnail route will be different than the actual form submission route. Use some workarounds (for example, have a secondary hidden form, and the blur event copies the file-upload onto it, and then submits it).