Introduction: In this article I have
explained How to validate image size and type of the file using jquery before
actually uploading on server. Image preview will also be shown if image is of
specified size and type.
In previous articles i explained How to Maintain image on postback in fileupload control in asp.net and Drag & drop to upload multiple files using ajaxfileupload like facebook in asp.net and Resize image in asp.net and Validate, upload, crop and store image in folder in asp.net using jquery and Upload, save image in folder and path in sql server database and retrieve using asp.net
Description: It is very common requirement while working on
asp.net project to upload image files e.g. jpg, jpeg, png, bmp, gif etc. I got the same
requirement where user can upload images. But I have to restrict user to upload
only certain type of imagesand of up to specified size.
Actually this can be done both server
side and client side. But to check the file type or size of file at server size
through code, file must be first uploaded into server memory which is time
consuming if the size of the file is large. So it will definitely degrade the
performance of our application. To overcome this problem we can validate file
type and size at client side using jQuery before actually uploading the image.
Implementation: Let’s create a sample
page to demonstrate the concept
HTML Source
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<style type="text/css">
.error {
background-color: #d9534f;
font-weight: 300;
font-size: 12px;
padding: 3px 6px 3px 6px;
color: #fff;
text-align: center;
white-space: nowrap;
}
</style>
<script src="http://code.jquery.com/jquery-1.11.3.js" type="text/javascript"></script>
<script type="text/javascript">
//Validate image size before
upload
function validateTypeAndSize(uploadCtrl) {
//
Get uploaded file extension
var extension = $(uploadCtrl).val().split('.').pop().toLowerCase();
//
Create array with the files extensions that we wish to upload
var validFileExtensions = ['jpeg', 'jpg', 'png', 'bmp'];
//Check
file extension in the array.if -1 that means the file extension is not in the
list.
if ($.inArray(extension, validFileExtensions) == -1) {
$('#spnMessage').text("Sorry!! Upload only jpg, jpeg, png, bmp image").show();
//
Clear fileuload control selected file
$(uploadCtrl).replaceWith($(uploadCtrl).val('').clone(true));
//Disable
Submit Button
$('#btnSubmit').prop('disabled', true);
//Clear
Image preview
$('#imgPreview').prop('src', '');
}
else {
//
Check and restrict the file size to 32 KB.
if ($(uploadCtrl).get(0).files[0].size > (32768)) {
$('#spnMessage').text("Sorry!! Max allowed image size is 32 kb").show();
// Clear fileuload control selected file
$(uploadCtrl).replaceWith($(uploadCtrl).val('').clone(true));
//Disable Submit Button
$('#btnSubmit').prop('disabled', true);
//Clear Image preview
$('#imgPreview').prop('src', '');
}
else {
//Clear and Hide message span
$('#spnMessage').text('').hide();
//Enable Submit Button
$('#btnSubmit').prop('disabled', false);
//Preview Image if valid
previewImage(uploadCtrl);
}
}
}
//Preview image before upload
function previewImage(input) {
if (input.files && input.files[0]) {
var reader = new FileReader();
reader.onload = function (e) {
$('#imgPreview')
.attr('src', e.target.result)
.width(200)
.height(150);
};
reader.readAsDataURL(input.files[0]);
}
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div style="text-align:center">
<asp:Image ID="imgPreview" Height="150px" Width="200px" runat="server" ClientIDMode="Static" /><br />
<asp:FileUpload ID="FileUpload1" runat="server" onchange="validateTypeAndSize(this)" /><br />
<br />
<asp:Button ID="btnSubmit" runat="server" Text="Submit" Enabled="false" ClientIDMode="Static" /><p>
<span id="spnMessage" class="error" style="display: none;"></span></p>
</div>
</form>
</body>
</html>
Explanation: User can now upload file of jpg, jpeg, png, gif, bmp type and up to 32 kb size. If
user selects any other file or large file than the specified limit then
appropriate message will be displayed to user and submit button will be
disabled. When a valid file of up to specified size is uploaded then submit
button will be enabled and image preview will be shown.
Note: I have restricted user to upload up to 32kb file. If you want to
restrict the file size to 2 mb then replace 32768 with 1024*1024*2 in above
jquery script.
Now over to you:
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