First we need a simple HTML input:
<input type="file" id="file" />
and then we add the javascript:
var _URL = window.URL || window.webkitURL;
$("#file").change(function(e) {
var file, img;
if ((file = this.files[0])) {
img = new Image();
img.onload = function() {
alert(this.width + " " + this.height);
};
img.onerror = function() {
alert( "not a valid file: " + file.type);
};
img.src = _URL.createObjectURL(file);
}
});
This shows the uploaded image's WxH in an alert.