to resize image in javascript:
$(window).load(function() {
mitad();doble();
});
function mitad(){
imag0.width=imag0.width/2;
imag0.height=imag0.height/2;
}
function doble(){
imag0.width=imag0.width*2;
imag0.height=imag0.height*2;}
imag0 is the name of the image:
<img src="xxx.jpg" name="imag0">