获取上传图片的宽高

<input name="pic" id="pic"  type="file">

<script>

$('#pic').change(function(){

var file = this;
createReader(file.files[0], function (w, h) { 
alert(w + ' '+ h);
});
  })
createReader = function(file, whenReady) {
    var reader = new FileReader;
    reader.onload = function (evt) {
        var image = new Image();
        image.onload = function () {
            var width = this.width;
            var height = this.height;
            if (whenReady) whenReady(width, height);
        };
        image.src = evt.target.result;
    };
    reader.readAsDataURL(file);

}

</script>