Accessing function results from another function?

I have these functions

function readURL(input) {
    if (input.files && input.files[0]) {
        var reader = new FileReader();

        reader.onload = function (e) {

            var img = new Image;
            img.src = reader.result;

            var imgwidth = img.width;
            var imgheight = img.height;
            console.log(imgwidth);
            console.log(imgheight);

            $('#imgcrop').attr('src', e.target.result);
            $('#preview').attr('src', e.target.result);
            $('.crop').Jcrop({

                onSelect: updateCoords,
                boxWidth: 300,
                boxHeight: 300,
                onChange: showPreview,
                aspectRatio: 1,
                bgOpacity:   .4,
                setSelect:   [ 100, 100, 50, 50 ]
            });
        };

        reader.readAsDataURL(input.files[0]);
    }
}

$("#imgInp").change(function() {
    console.log(this);
    readURL(this);
});

function updateCoords(c) {
    console.log(c);
    $('#x').val(c.x);
    $('#y').val(c.y);
    $('#w').val(c.w);
    $('#h').val(c.h);
}

function showPreview(coords) {
    var rx = 100 / coords.w;
    var ry = 100 / coords.h;

    $('#preview').css({
        width: Math.round(rx * imgwidth) + 'px',
        height: Math.round(ry * imgheight) + 'px',
        marginLeft: '-' + Math.round(rx * coords.x) + 'px',
        marginTop: '-' + Math.round(ry * coords.y) + 'px'
    });
}

And I need to access imgwidth and imgheight from the file reader function to use in the showpreview function, but I'm having trouble with the scope of those functions. How can I access these values, or at least pass them as parameters to use in the other function?

Thanks!